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Sample records for blood flow controls

  1. Local Control of Blood Flow

    Science.gov (United States)

    Clifford, Philip S.

    2011-01-01

    Organ blood flow is determined by perfusion pressure and vasomotor tone in the resistance vessels of the organ. Local factors that regulate vasomotor tone include myogenic and metabolic autoregulation, flow-mediated and conducted responses, and vasoactive substances released from red blood cells. The relative importance of each of these factors…

  2. Glial and neuronal control of brain blood flow

    DEFF Research Database (Denmark)

    Attwell, David; Buchan, Alastair M; Charpak, Serge

    2010-01-01

    Blood flow in the brain is regulated by neurons and astrocytes. Knowledge of how these cells control blood flow is crucial for understanding how neural computation is powered, for interpreting functional imaging scans of brains, and for developing treatments for neurological disorders. It is now...... in our understanding of cerebral blood flow control have important implications for the development of new therapeutic approaches....

  3. Synthetic Capillaries to Control Microscopic Blood Flow

    Science.gov (United States)

    Sarveswaran, K.; Kurz, V.; Dong, Z.; Tanaka, T.; Penny, S.; Timp, G.

    2016-02-01

    Capillaries pervade human physiology. The mean intercapillary distance is only about 100 μm in human tissue, which indicates the extent of nutrient diffusion. In engineered tissue the lack of capillaries, along with the associated perfusion, is problematic because it leads to hypoxic stress and necrosis. However, a capillary is not easy to engineer due to its complex cytoarchitecture. Here, it is shown that it is possible to create in vitro, in about 30 min, a tubular microenvironment with an elastic modulus and porosity consistent with human tissue that functionally mimicks a bona fide capillary using “live cell lithography”(LCL) to control the type and position of cells on a composite hydrogel scaffold. Furthermore, it is established that these constructs support the forces associated with blood flow, and produce nutrient gradients similar to those measured in vivo. With LCL, capillaries can be constructed with single cell precision—no other method for tissue engineering offers such precision. Since the time required for assembly scales with the number of cells, this method is likely to be adapted first to create minimal functional units of human tissue that constitute organs, consisting of a heterogeneous population of 100–1000 cells, organized hierarchically to express a predictable function.

  4. Glial and neuronal control of brain blood flow

    DEFF Research Database (Denmark)

    Attwell, David; Buchan, Alastair M; Charpak, Serge

    2010-01-01

    Blood flow in the brain is regulated by neurons and astrocytes. Knowledge of how these cells control blood flow is crucial for understanding how neural computation is powered, for interpreting functional imaging scans of brains, and for developing treatments for neurological disorders. It is now...

  5. Blood flow controls bone vascular function and osteogenesis

    Science.gov (United States)

    Ramasamy, Saravana K.; Kusumbe, Anjali P.; Schiller, Maria; Zeuschner, Dagmar; Bixel, M. Gabriele; Milia, Carlo; Gamrekelashvili, Jaba; Limbourg, Anne; Medvinsky, Alexander; Santoro, Massimo M.; Limbourg, Florian P.; Adams, Ralf H.

    2016-01-01

    While blood vessels play important roles in bone homeostasis and repair, fundamental aspects of vascular function in the skeletal system remain poorly understood. Here we show that the long bone vasculature generates a peculiar flow pattern, which is important for proper angiogenesis. Intravital imaging reveals that vessel growth in murine long bone involves the extension and anastomotic fusion of endothelial buds. Impaired blood flow leads to defective angiogenesis and osteogenesis, and downregulation of Notch signalling in endothelial cells. In aged mice, skeletal blood flow and endothelial Notch activity are also reduced leading to decreased angiogenesis and osteogenesis, which is reverted by genetic reactivation of Notch. Blood flow and angiogenesis in aged mice are also enhanced on administration of bisphosphonate, a class of drugs frequently used for the treatment of osteoporosis. We propose that blood flow and endothelial Notch signalling are key factors controlling ageing processes in the skeletal system. PMID:27922003

  6. Peripheral blood flow control in diabetes mellitus

    DEFF Research Database (Denmark)

    Hilsted, Jannik

    1991-01-01

    Long term diabetes has a profound effect on the peripheral circulation. This has been demonstrated to be due to the presence of angiopathy and autonomic neuropathy, affecting autoregulation and distensibility of the vessels as well as local and central reflex regulation of the vascular resistance....... Whereas the hemodynamic consequences of vascular denervation are well known (causing blood pressure maladaptation to a number of stimuli such as standing, exercise and agonist infusion) (Hilsted 1985), the consequences of disturbances in autoregulation and distensibility remain to be established....

  7. Metabolic control of muscle blood flow during exercise in humans

    DEFF Research Database (Denmark)

    Boushel, Robert Christopher

    2003-01-01

    and the vasculature that induce vasodilation. A link between muscle metabolic events and microvascular control of blood flow is illustrated by local dilation of terminal arterioles during contraction of muscle fibers and conduction of vasodilation upstream. Endothelial-derived vasodilator mechanisms are known...... to exert control of muscle vasodilation. Adenosine, nitric oxide (NO), prostacyclin (PGI2), and endothelial-derived hyperpolarization factor (EDHF) are possible mediators of muscle vasodilation during exercise. In humans, adenosine has been shown to contribute to functional hyperemia as blood flow...

  8. Cerebral autoregulation control of blood flow in the brain

    CERN Document Server

    Payne, Stephen

    2016-01-01

    This Brief provides a comprehensive introduction to the control of blood flow in the brain. Beginning with the basic physiology of autoregulation, the author goes on to discuss measurement techniques, mathematical models, methods of analysis, and relevant clinical conditions, all within this single volume. The author draws together this disparate field, and lays the groundwork for future research directions. The text gives an up-to-date review of the state of the art in cerebral autoregulation, which is particularly relevant as cerebral autoregulation moves from the laboratory to the bedside. Cerebral Autoregulation will be useful to researchers in the physical sciences such as mathematical biology, medical physics, and biomedical engineering whose work is concerned with the brain. Researchers in the medical sciences and clinicians dealing with the brain and blood flow, as well as industry professionals developing techniques such as ultrasound, MRI, and CT will also find this Brief of interest.

  9. Observer-based Controller For Microrobot in Pulsatile Blood Flow

    OpenAIRE

    Sadelli, Lounis; Fruchard, Matthieu; Ferreira, Antoine

    2014-01-01

    International audience; We propose an observer-based controller for a magnetic microrobot immersed in the human vasculature. The drag force depends on the pulsatile blood velocity and specially acts on the microrobot dynamics. In the design of advanced control laws, the blood velocity is usually assumed to be known or set to a constant mean value to achieve the control objectives, whereas the sole robot position is measured. We prove the stability of the proposed observer-based controller com...

  10. Unveiling astrocytic control of cerebral blood flow with optogenetics.

    Science.gov (United States)

    Masamoto, Kazuto; Unekawa, Miyuki; Watanabe, Tatsushi; Toriumi, Haruki; Takuwa, Hiroyuki; Kawaguchi, Hiroshi; Kanno, Iwao; Matsui, Ko; Tanaka, Kenji F; Tomita, Yutaka; Suzuki, Norihiro

    2015-06-16

    Cortical neural activities lead to changes in the cerebral blood flow (CBF), which involves astrocytic control of cerebrovascular tone. However, the manner in which astrocytic activity specifically leads to vasodilation or vasoconstriction is difficult to determine. Here, cortical astrocytes genetically expressing a light-sensitive cation channel, channelrhodopsin-2 (ChR2), were transcranially activated with a blue laser while the spatiotemporal changes in CBF were noninvasively monitored with laser speckle flowgraphy in the anesthetised mouse cortex. A brief photostimulation induced a fast transient increase in CBF. The average response onset time was 0.7 ± 0.7 sec at the activation foci, and this CBF increase spread widely from the irradiation spot with an apparent propagation speed of 0.8-1.1 mm/sec. The broad increase in the CBF could be due to a propagation of diffusible vasoactive signals derived from the stimulated astrocytes. Pharmacological manipulation showed that topical administration of a K(+) channel inhibitor (BaCl2; 0.1-0.5 mM) significantly reduced the photostimulation-induced CBF responses, which indicates that the ChR2-evoked astrocytic activity involves K(+) signalling to the vascular smooth muscle cells. These findings demonstrate a unique model for exploring the role of the astrocytes in gliovascular coupling using non-invasive, time-controlled, cell-type specific perturbations.

  11. Sympathetic reflex control of blood flow in human peripheral tissues

    DEFF Research Database (Denmark)

    Henriksen, O

    1991-01-01

    Sympathetic vasoconstrictor reflexes are essential for the maintenance of arterial blood pressure in upright position. It has been generally believed that supraspinal sympathetic vasoconstrictor reflexes elicited by changes in baroreceptor activity play an important role. Recent studies on human...... sympathetic vasoconstrictor reflexes are blocked. Blood flow has been measure by the local 133Xe-technique. The results indicate the presence of spinal as well as supraspinal sympathetic vasoconstrictor reflexes to human peripheral tissues. Especially is emphasized the presence of a local sympathetic veno...

  12. Intensive blood pressure control affects cerebral blood flow in type 2 diabetes mellitus patients

    DEFF Research Database (Denmark)

    Kim, Yu-Sok; Davis, Shyrin C A T; Truijen, Jasper;

    2011-01-01

    Type 2 diabetes mellitus is associated with microvascular complications, hypertension, and impaired dynamic cerebral autoregulation. Intensive blood pressure (BP) control in hypertensive type 2 diabetic patients reduces their risk of stroke but may affect cerebral perfusion. Systemic hemodynamic...... variables and transcranial Doppler-determined cerebral blood flow velocity (CBFV), cerebral CO2 responsiveness, and cognitive function were determined after 3 and 6 months of intensive BP control in 17 type 2 diabetic patients with microvascular complications (T2DM+), in 18 diabetic patients without (T2DM......-) microvascular complications, and in 16 nondiabetic hypertensive patients. Cerebrovascular reserve capacity was lower in T2DM+ versus T2DM- and nondiabetic hypertensive patients (4.6±1.1 versus 6.0±1.6 [P

  13. Oscillations and chaos in renal blood flow control

    DEFF Research Database (Denmark)

    Holstein-Rathlou, N H

    1993-01-01

    In normotensive, halothane-anesthetized rats, oscillations can be found both in the single-nephron blood flow and in the tubular pressure. Experimental data and computer simulations support the hypothesis that the oscillations are caused by the tubuloglomerular feedback (TGF) mechanism. Model...... to the other. In renovascular and spontaneously hypertensive rats, regular oscillations give way to highly irregular, chaotic fluctuations. The chaotic fluctuations appear to have the same mechanism as the regular TGF-mediated oscillations. The irregular fluctuations most likely represent a parameter...

  14. Fibro-Vascular Coupling in the Control of Cochlear Blood Flow

    OpenAIRE

    Min Dai; Xiaorui Shi

    2011-01-01

    BACKGROUND: Transduction of sound in the cochlea is metabolically demanding. The lateral wall and hair cells are critically vulnerable to hypoxia, especially at high sound levels, and tight control over cochlear blood flow (CBF) is a physiological necessity. Yet despite the importance of CBF for hearing, consensus on what mechanisms are involved has not been obtained. METHODOLOGY/PRINCIPAL FINDINGS: We report on a local control mechanism for regulating inner ear blood flow involving fibrocyte...

  15. Modeling Cerebral Blood Flow Control During Posture Change from Sitting to Standing

    DEFF Research Database (Denmark)

    Olufsen, Mette; Tran, Hien; Ottesen, Johnny T.

    2004-01-01

    , the heart, and venous valves. We use physiologically based control mechanisms to describe the regulation of cerebral blood velocity and arterial pressure in response to orthostatic hypotension resulting from postural change. Beyond active control mechanisms we also have to include certain passive non......Hypertension, decreased cerebral blood flow, and diminished cerebral blood flow regulation, are among the first signs indicating the presence of cerebral vascular disease. In this paper, we will present a mathematical model that can predict blood flow and pressure during posture change from sitting......-linearities in some of the compliance-pressure and resistance-pressure relationships. Futhermore, an acurate and physiologically based submodel, describing the dynamics of how gravity effects the blood distribution during suspine changes, is included. To justify the fidelity of our mathematical model and control...

  16. Minimal sensor count approach to fuzzy logic rotary blood pump flow control.

    Science.gov (United States)

    Casas, Fernando; Ahmed, Nisar; Reeves, Andrew

    2007-01-01

    A rotary blood pump fuzzy logic flow controller without flow sensors was developed and tested in vitro. The controller, implemented in LabView, was set to maintain a flow set point in the presence of external pressure disturbances. Flow was estimated as a function of measured pump's delta P and speed, using a steady-state, nonlinear approximation. The fuzzy controller used the pump's flow estimate and delta P as feedback variables. The defuzzified control output manipulated the pump speed. Membership functions included flow error, delta P, and pump speed. Experimental runs in a mock loop (water/glycerin 3.5 cPs, 37 degrees C), using the estimated flow, were compared with those using a Transonic flow meter for nine conditions of flow and delta P (4 to 6 L/min, 150 to 350 mm Hg). Pressure disturbances generated by a servo pinch valve ranged from +/-23 to +/-47 mm Hg. Results indicated that the fuzzy controller ably regulated the flow set point to within +/-10% of the baseline even under large swings in pressure. There was no difference in controller performance between the ultrasonic flow measurement and the estimated flow calculation scenarios. These tests demonstrated that the fuzzy controller is capable of rejecting disturbances and regulating flow to acceptable limits while using a flow estimate.

  17. Sympathetic reflex control of blood flow in human peripheral tissues

    DEFF Research Database (Denmark)

    Henriksen, O

    1991-01-01

    Sympathetic vasoconstrictor reflexes are essential for the maintenance of arterial blood pressure in upright position. It has been generally believed that supraspinal sympathetic vasoconstrictor reflexes elicited by changes in baroreceptor activity play an important role. Recent studies on human ...... to collision of normodromically and antidromically conducted impulses in efferent sympathetic vasoconstrictor fibers. The evidence obtained suggests that sympathetic vasoconstrictor reflexes to postural changes are complex and highly differentiated....

  18. Metabolic control of resting hemispheric cerebral blood flow is oxidative, not glycolytic

    OpenAIRE

    Powers, William. J.; Videen, Tom O.; Markham, Joanne; Walter, Vonn; Perlmutter, Joel S.

    2011-01-01

    Although the close regional coupling of resting cerebral blood flow (CBF) with both cerebral metabolic rate of oxygen (CMRO2) and cerebral metabolic rate of glucose (CMRglc) within individuals is well documented, there are few data regarding the coupling between whole brain flow and metabolism among different subjects. To investigate the metabolic control of resting whole brain CBF, we performed multivariate analysis of hemispheric CMRO2, CMRglc, and other covariates as predictors of resting ...

  19. Influence of skin temperature on central thermoregulatory control of leg blood flow.

    Science.gov (United States)

    Proppe, D W

    1981-05-01

    This study examined the influence of elevated skin temperature (Tsk) on the central thermoregulatory control of leg blood flow in five unanesthetized, chronically instrumented, resting baboons (Papio anubis and P. cynocephalus). In each experiment, mean iliac blood flow (MIBF), mean arterial blood pressure, arterial blood temperature (Tbl), and Tsk were measured, and iliac vascular conductance (IVC) was calculated. A heat exchanger was incorporated into a chronic arteriovenous femoral shunt to control Tbl. The protocol consisted of raising Tbl approximately 2.6 degrees C in thermoneutral environment (cool Tsk) an then again after Tsk had been elevated by environmental heating. A major influence of raising Tsk was the lowering of threshold Tbl at which the rise in MIBF and IVC commenced. This threshold Tbl was lowered at least 0.8 degrees C on the average. Also, over the whole range of Tbl studied (37.0-39.6 degrees C), MIBF and IVC were higher at high Tsk than at cool Tsk. Thus an elevation of Tsk significantly influences the control of skin blood flow by central thermoreceptors.

  20. Eppur Si Muove: The dynamic nature of physiological control of renal blood flow by the renal sympathetic nerves.

    Science.gov (United States)

    Schiller, Alicia M; Pellegrino, Peter Ricci; Zucker, Irving H

    2016-08-03

    Tubuloglomerular feedback and the myogenic response are widely appreciated as important regulators of renal blood flow, but the role of the sympathetic nervous system in physiological renal blood flow control remains controversial. Where classic studies using static measures of renal blood flow failed, dynamic approaches have succeeded in demonstrating sympathetic control of renal blood flow under normal physiological conditions. This review focuses on transfer function analysis of renal pressure-flow, which leverages the physical relationship between blood pressure and flow to assess the underlying vascular control mechanisms. Studies using this approach indicate that the renal nerves are important in the rapid regulation of the renal vasculature. Animals with intact renal innervation show a sympathetic signature in the frequency range associated with sympathetic vasomotion that is eliminated by renal denervation. In conscious rabbits, this sympathetic signature exerts vasoconstrictive, baroreflex control of renal vascular conductance, matching well with the rhythmic, baroreflex-influenced control of renal sympathetic nerve activity and complementing findings from other studies employing dynamic approaches to study renal sympathetic vascular control. In this light, classic studies reporting that nerve stimulation and renal denervation do not affect static measures of renal blood flow provide evidence for the strength of renal autoregulation rather than evidence against physiological renal sympathetic control of renal blood flow. Thus, alongside tubuloglomerular feedback and the myogenic response, renal sympathetic outflow should be considered an important physiological regulator of renal blood flow. Clinically, renal sympathetic vasomotion may be important for solving the problems facing the field of therapeutic renal denervation.

  1. Biomimetic approaches for green tribology: from the lotus effect to blood flow control

    Science.gov (United States)

    Maani, Nazanin; Rayz, Vitaliy S.; Nosonovsky, Michael

    2015-09-01

    The research in Green tribology combines several areas including biomimetic tribomaterials and surfaces for controlled adhesion. Biomimetic surfaces mimic living nature and thus they are eco-friendly. The most famous biomimetic surface effect is the Lotus effect (reduction of water adhesion to a solid surface due to micro/nanostructuring of the solid surface). Several extensions of the Lotus effect have been discussed in the literature including the oleophobicity (repelling organic liquids such as oils), underwater oleophobicity to reduce fouling, and the shark skin effect (flow drag reduction due to specially oriented micro-riblets). Here we suggest a potentially important application of micro/nanostructured surfaces in the biomedical area: the micro/nanostructure controlled adhesion in blood flow. Blood is a suspension, and its adhesion properties are different from those of water and oil. For many cardiovascular applications, it is desirable to reduce stagnation and clotting of blood. Therefore, both the underwater oleophobicuity and shark-skin effect can be used. We discuss how computational fluid dynamics models can be used to investigate the structure-property relationships of surface pattern-controlled blood flow adhesion.

  2. A model for investigating the control of muscle blood flow: the masseteric artery in conscious rabbits.

    Science.gov (United States)

    Roatta, S; Mohammed, M; Turturici, M; Milano, L; Passatore, M

    2010-09-01

    The complex interplay of neural, metabolic, myogenic and mechanical mechanisms that regulate blood flow in skeletal muscle (MBF) is still incompletely understood. For the first time, a method is presented for high time-resolution recording of MBF from a purely muscular artery in physiological conditions. Ultrasound perivascular flow probes were implanted (n = 15) mono- or bilaterally around the masseteric branch of the facial artery in nine rabbits and tested up to 16 days after implant. Reliable and stable recordings were achieved in 50% of implants. Blood flow was observed to increase from a resting level of 0.2-0.3 ml min(-1) up to 4.0-6.0 ml min(-1) during spontaneous masticatory activity. In addition, within single masticatory cycles marked back flow transients could be observed (peak flow = -10 ml min(-1)) during powerful masticatory strokes but not during mild mastication. The possibility of (1) surgically removing the sympathetic supply to the relevant vascular bed and of (2) bilaterally monitoring the perfusion of masseter muscles thus allowing to use one side as control side for different types of interventions makes this model a useful tool for disentangling the different mechanisms involved in the control of MBF.

  3. Sympathetic reflex control of subcutaneous blood flow in tetraplegic man during postural changes

    DEFF Research Database (Denmark)

    Skagen, K; Jensen, K; Henriksen, O

    1982-01-01

    1. The effect of head-up tilt upon subcutaneous blood flow in the distal arm and leg was studied in 12 patients with complete traumatic spinal cord transection at the cervical level. 2. Blood flow was measured by the local 133Xe washout technique. 3. Leg lowering induced a 47% decrease in blood f...

  4. Platelet adhesion from shear blood flow is controlled by near-wall rebounding collisions with erythrocytes.

    Science.gov (United States)

    Tokarev, A A; Butylin, A A; Ataullakhanov, F I

    2011-02-16

    The efficacy of platelet adhesion in shear flow is known to be substantially modulated by the physical presence of red blood cells (RBCs). The mechanisms of this regulation remain obscure due to the complicated character of platelet interactions with RBCs and vascular walls. To investigate this problem, we have created a mathematical model that takes into account shear-induced transport of platelets across the flow, platelet expulsion by the RBCs from the near-wall layer of the flow onto the wall, and reversible capture of platelets by the wall and their firm adhesion to it. This model analysis allowed us to obtain, for the first time to our knowledge, an analytical determination of the platelet adhesion rate constant as a function of the wall shear rate, hematocrit, and average sizes of platelets and RBCs. This formula provided a quantitative description of the results of previous in vitro adhesion experiments in perfusion chambers. The results of the simulations suggest that under a wide range of shear rates and hematocrit values, the rate of platelet adhesion from the blood flow is mainly limited by the frequency of their near-wall rebounding collisions with RBCs. This finding reveals the mechanism by which erythrocytes physically control platelet hemostasis.

  5. Hyperhomocysteinemia decreases bone blood flow

    Directory of Open Access Journals (Sweden)

    Neetu T

    2011-01-01

    Full Text Available Neetu Tyagi*, Thomas P Vacek*, John T Fleming, Jonathan C Vacek, Suresh C TyagiDepartment of Physiology and Biophysics, School of Medicine, University of Louisville, Louisville, KY, USA *These authors have equal authorshipAbstract: Elevated plasma levels of homocysteine (Hcy, known as hyperhomocysteinemia (HHcy, are associated with osteoporosis. A decrease in bone blood flow is a potential cause of compromised bone mechanical properties. Therefore, we hypothesized that HHcy decreases bone blood flow and biomechanical properties. To test this hypothesis, male Sprague–Dawley rats were treated with Hcy (0.67 g/L in drinking water for 8 weeks. Age-matched rats served as controls. At the end of the treatment period, the rats were anesthetized. Blood samples were collected from experimental or control rats. Biochemical turnover markers (body weight, Hcy, vitamin B12, and folate were measured. Systolic blood pressure was measured from the right carotid artery. Tibia blood flow was measured by laser Doppler flow probe. The results indicated that Hcy levels were significantly higher in the Hcy-treated group than in control rats, whereas vitamin B12 levels were lower in the Hcy-treated group compared with control rats. There was no significant difference in folate concentration and blood pressure in Hcy-treated versus control rats. The tibial blood flow index of the control group was significantly higher (0.78 ± 0.09 flow unit compared with the Hcy-treated group (0.51 ± 0.09. The tibial mass was 1.1 ± 0.1 g in the control group and 0.9 ± 0.1 in the Hcy-treated group. The tibia bone density was unchanged in Hcy-treated rats. These results suggest that Hcy causes a reduction in bone blood flow, which contributes to compromised bone biomechanical properties.Keywords: homocysteine, tibia, bone density

  6. Fibro-vascular coupling in the control of cochlear blood flow.

    Directory of Open Access Journals (Sweden)

    Min Dai

    Full Text Available BACKGROUND: Transduction of sound in the cochlea is metabolically demanding. The lateral wall and hair cells are critically vulnerable to hypoxia, especially at high sound levels, and tight control over cochlear blood flow (CBF is a physiological necessity. Yet despite the importance of CBF for hearing, consensus on what mechanisms are involved has not been obtained. METHODOLOGY/PRINCIPAL FINDINGS: We report on a local control mechanism for regulating inner ear blood flow involving fibrocyte signaling. Fibrocytes in the super-strial region are spatially distributed near pre-capillaries of the spiral ligament of the albino guinea pig cochlear lateral wall, as demonstrably shown in transmission electron microscope and confocal images. Immunohistochemical techniques reveal the inter-connected fibrocytes to be positive for Na+/K+ ATPase β1 and S100. The connected fibrocytes display more Ca(2+ signaling than other cells in the cochlear lateral wall as indicated by fluorescence of a Ca(2+ sensor, fluo-4. Elevation of Ca(2+ in fibrocytes, induced by photolytic uncaging of the divalent ion chelator o-nitrophenyl EGTA, results in propagation of a Ca(2+ signal to neighboring vascular cells and vasodilation in capillaries. Of more physiological significance, fibrocyte to vascular cell coupled signaling was found to mediate the sound stimulated increase in cochlear blood flow (CBF. Cyclooxygenase-1 (COX-1 was required for capillary dilation. CONCLUSIONS/SIGNIFICANCE: The findings provide the first evidence that signaling between fibrocytes and vascular cells modulates CBF and is a key mechanism for meeting the cellular metabolic demand of increased sound activity.

  7. Resting cerebral blood flow

    Science.gov (United States)

    Ances, B M.; Sisti, D; Vaida, F; Liang, C L.; Leontiev, O; Perthen, J E.; Buxton, R B.; Benson, D; Smith, D M.; Little, S J.; Richman, D D.; Moore, D J.; Ellis, R J.

    2009-01-01

    Objective: HIV enters the brain soon after infection causing neuronal damage and microglial/astrocyte dysfunction leading to neuropsychological impairment. We examined the impact of HIV on resting cerebral blood flow (rCBF) within the lenticular nuclei (LN) and visual cortex (VC). Methods: This cross-sectional study used arterial spin labeling MRI (ASL-MRI) to measure rCBF within 33 HIV+ and 26 HIV− subjects. Nonparametric Wilcoxon rank sum test assessed rCBF differences due to HIV serostatus. Classification and regression tree (CART) analysis determined optimal rCBF cutoffs for differentiating HIV serostatus. The effects of neuropsychological impairment and infection duration on rCBF were evaluated. Results: rCBF within the LN and VC were significantly reduced for HIV+ compared to HIV− subjects. A 2-tiered CART approach using either LN rCBF ≤50.09 mL/100 mL/min or LN rCBF >50.09 mL/100 mL/min but VC rCBF ≤37.05 mL/100 mL/min yielded an 88% (29/33) sensitivity and an 88% (23/26) specificity for differentiating by HIV serostatus. HIV+ subjects, including neuropsychologically unimpaired, had reduced rCBF within the LN (p = 0.02) and VC (p = 0.001) compared to HIV− controls. A temporal progression of brain involvement occurred with LN rCBF significantly reduced for both acute/early (<1 year of seroconversion) and chronic HIV-infected subjects, whereas rCBF in the VC was diminished for only chronic HIV-infected subjects. Conclusion: Resting cerebral blood flow (rCBF) using arterial spin labeling MRI has the potential to be a noninvasive neuroimaging biomarker for assessing HIV in the brain. rCBF reductions that occur soon after seroconversion possibly reflect neuronal or vascular injury among HIV+ individuals not yet expressing neuropsychological impairment. GLOSSARY AEH = acute/early HIV infection; ANOVA = analysis of variance; ASL-MRI = arterial spin labeling MRI; CART = classification and regression tree; CBF = cerebral blood flow; CH = chronic HIV

  8. Metabolic control of resting hemispheric cerebral blood flow is oxidative, not glycolytic.

    Science.gov (United States)

    Powers, William J; Videen, Tom O; Markham, Joanne; Walter, Vonn; Perlmutter, Joel S

    2011-05-01

    Although the close regional coupling of resting cerebral blood flow (CBF) with both cerebral metabolic rate of oxygen (CMRO(2)) and cerebral metabolic rate of glucose (CMRglc) within individuals is well documented, there are few data regarding the coupling between whole brain flow and metabolism among different subjects. To investigate the metabolic control of resting whole brain CBF, we performed multivariate analysis of hemispheric CMRO(2), CMRglc, and other covariates as predictors of resting CBF among 23 normal humans. The univariate analysis showed that only CMRO(2) was a significant predictor of CBF. The final multivariate model contained two additional terms in addition to CMRO(2): arterial oxygen content and oxygen extraction fraction. Notably, arterial plasma glucose concentration and CMRglc were not included in the final model. Our data demonstrate that the metabolic factor controlling hemispheric CBF in the normal resting brain is CMRO(2) and that CMRglc does not make a contribution. Our findings provide evidence for compartmentalization of brain metabolism into a basal component in which CBF is coupled to oxygen metabolism and an activation component in which CBF is controlled by another mechanism.

  9. Open-loop (feed-forward) and feedback control of coronary blood flow during exercise, cardiac pacing, and pressure changes.

    Science.gov (United States)

    Pradhan, Ranjan K; Feigl, Eric O; Gorman, Mark W; Brengelmann, George L; Beard, Daniel A

    2016-06-01

    A control system model was developed to analyze data on in vivo coronary blood flow regulation and to probe how different mechanisms work together to control coronary flow from rest to exercise, and under a variety of experimental conditions, including cardiac pacing and with changes in coronary arterial pressure (autoregulation). In the model coronary flow is determined by the combined action of a feedback pathway signal that is determined by the level of plasma ATP in coronary venous blood, an adrenergic open-loop (feed-forward) signal that increases with exercise, and a contribution of pressure-mediated myogenic control. The model was identified based on data from exercise experiments where myocardial oxygen extraction, coronary flow, cardiac interstitial norepinephrine concentration, and arterial and coronary venous plasma ATP concentrations were measured during control and during adrenergic and purinergic receptor blockade conditions. The identified model was used to quantify the relative contributions of open-loop and feedback pathways and to illustrate the degree of redundancy in the control of coronary flow. The results indicate that the adrenergic open-loop control component is responsible for most of the increase in coronary blood flow that occurs during high levels of exercise. However, the adenine nucleotide-mediated metabolic feedback control component is essential. The model was evaluated by predicting coronary flow in cardiac pacing and autoregulation experiments with reasonable fits to the data. The analysis shows that a model in which coronary venous plasma adenine nucleotides are a signal in local metabolic feedback control of coronary flow is consistent with the available data.

  10. Pulmonary blood flow and its distribution in highly trained endurance athletes and healthy control subjects

    NARCIS (Netherlands)

    I. Heinonen (Ilkka); M.J. Savolainen (Markku); C. Han (Chunlei); J. Kemppainen (Jukka); V. Oikonen (Vesa); M. Luotolahti (Matti); D.J.G.M. Duncker (Dirk); D. Merkus (Daphne); J. Knuuti (Juhani); K.K. Kalliokoski (Kari)

    2013-01-01

    textabstractPulmonary blood flow (PBF) is an important determinant of endurance sports performance, yet studies investigating adaptations of the pulmonary circulation in athletes are scarce. In the present study, we investigated PBF, its distribution, and heterogeneity at baseline and during intrave

  11. Blood flow and microgravity

    Science.gov (United States)

    Bureau, Lionel; Coupier, Gwennou; Dubois, Frank; Duperray, Alain; Farutin, Alexander; Minetti, Christophe; Misbah, Chaouqi; Podgorski, Thomas; Tsvirkun, Daria; Vysokikh, Mikhail

    2017-01-01

    The absence of gravity during space flight can alter cardio-vascular functions partially due to reduced physical activity. This affects the overall hemodynamics, and in particular the level of shear stresses to which blood vessels are submitted. Long-term exposure to space environment is thus susceptible to induce vascular remodeling through a mechanotransduction cascade that couples vessel shape and function with the mechanical cues exerted by the circulating cells on the vessel walls. Central to such processes, the glycocalyx - i.e. the micron-thick layer of biomacromolecules that lines the lumen of blood vessels and is directly exposed to blood flow - is a major actor in the regulation of biochemical and mechanical interactions. We discuss in this article several experiments performed under microgravity, such as the determination of lift force and collective motion in blood flow, and some preliminary results obtained in artificial microfluidic circuits functionalized with endothelium that offer interesting perspectives for the study of the interactions between blood and endothelium in healthy condition as well as by mimicking the degradation of glycocalyx caused by long space missions. A direct comparison between experiments and simulations is discussed. xml:lang="fr"

  12. Laser speckle contrast reveals cerebral blood flow dynamics evoked by optogenetically controlled neuronal activity

    Science.gov (United States)

    Li, Nan; Thakor, Nitish V.; Pelled, Galit

    2013-03-01

    As a critical basis of functional brain imaging, neurovascular coupling describes the link between neuronal and hemodynamic changes. The majority of in vivo neurovascular coupling studies was performed by inducing sensory stimulation via afferent inputs. Unfortunately such an approach results in recruiting of multiple types of cells, which confounds the explanation of neuronal roles in stimulus evoked hemodynamic changes. Recently optogenetics has emerged to provide immediate control of neurons by exciting or inhibiting genetically engineered neurons expressing light sensitive proteins. However, there is a need for optical methods capable of imaging the concurrent hemodynamic changes. We utilize laser speckle contrast imaging (LSCI) to obtain high resolution display of cerebral blood flow (CBF) in the vicinity of the targeted neural population. LSCI is a minimally invasive method for imaging CBF in microvessels through thinned skull, and produces images with high spatiotemporal resolution, wide field of view. In the integrated system light sources with different wavelengths and band-passing/blocking filters were used to allow simultaneous optical manipulation of neuronal activities and optical imaging of corresponding CBF. Experimental studies were carried out in a rodent model expressing channalrhodopsin (ChR2) in excitatory neurons in the somatosensory cortex (S1). The results demonstrated significant increases of CBF in response to ChR2 stimulation (exciting neuronal firing) comparable to the CBF response to contralateral forepaw stimulation. The approach promises to be an exciting minimally invasive method to study neurovascular coupling. The complete system provides a novel approach for broad neuroscience applications.

  13. Voluntary respiratory control and cerebral blood flow velocity upon ice-water immersion

    DEFF Research Database (Denmark)

    Mantoni, Teit; Rasmussen, Jakob Højlund; Belhage, Bo;

    2008-01-01

    INTRODUCTION: In non-habituated subjects, cold-shock response to cold-water immersion causes rapid reduction in cerebral blood flow velocity (approximately 50%) due to hyperventilation, increasing risk of syncope, aspiration, and drowning. Adaptation to the response is possible, but requires...... several cold immersions. This study examines whether thorough instruction enables non-habituated persons to attenuate the ventilatory component of cold-shock response. METHODS: There were nine volunteers (four women) who were lowered into a 0 degrees C immersion tank for 60 s. Middle cerebral artery mean......: Even without prior cold-water experience, subjects were able to suppress reflex hyperventilation following ice-water immersion, maintaining the cerebral blood flow velocity at a level not associated with impaired consciousness. This study implies that those susceptible to accidental cold...

  14. Flow Control

    Science.gov (United States)

    2013-04-08

    an aerodynamic design. A few examples of this type of flow control are winglets , fins, or dimples on a golf ball. The other type of flow control is...represented the density states of the flow field. The first parameter was the composition of the regression vector, Θ j. This regression vector was...Development Using Proper Orthogonal De- composition and Volterra Theory. In AIAA 2003-1922, 2003. A. Mani, M. Wang, and P. Moin. Resolution requirements

  15. Voluntary respiratory control and cerebral blood flow velocity upon ice-water immersion

    DEFF Research Database (Denmark)

    Mantoni, Teit; Rasmussen, Jakob Højlund; Belhage, Bo;

    2008-01-01

    In non-habituated subjects, cold-shock response to cold-water immersion causes rapid reduction in cerebral blood flow velocity (approximately 50%) due to hyperventilation, increasing risk of syncope, aspiration, and drowning. Adaptation to the response is possible, but requires several cold...... immersions. This study examines whether thorough instruction enables non-habituated persons to attenuate the ventilatory component of cold-shock response....

  16. Regional cerebral blood flow in schizophrenia

    Energy Technology Data Exchange (ETDEWEB)

    Mathew, R.J.; Duncan, G.C.; Weinman, M.L.; Barr, D.L.

    1982-10-01

    Regional cerebral blood flow (rCBF) was measured via xenon133 inhalation technique in 23 patients with schizophrenia and 18 age- and sex-matched controls. The mean blood flow to both hemispheres was found to be lower for the patients. The patients and their controls did not differ on interhemispheric differences in blood flow. There were no differences in rCBF between medicated and unmedicated, subchronic and chronic, and paranoid and nonparanoid patients. Hallucinations were associated with reduced blood flow to several postcentral regions.

  17. Deciphering the neuronal circuitry controlling local blood flow in the cerebral cortex with optogenetics in PV::Cre transgenic mice

    Directory of Open Access Journals (Sweden)

    Alan eUrban

    2012-06-01

    Full Text Available Although it is know since more than a century that neuronal activity is coupled to blood supply regulation, the underlying pathways remains to be identified. In the brain, neuronal activation triggers a local increase of cerebral blood flow (CBF that is controlled by the neurogliovascular unit composed of terminals of neurons, astrocytes and blood vessel muscles. It is generally accepted that the regulation of the neurogliovascular unit is adjusted to local metabolic demand by local circuits. Today experimental data led us to realize that the regulatory mechanisms are more complex and that a neuronal system within the brain is devoted to the control of local brain blood flow. Recent optogenetic experiments combined with functional magnetic resonance imaging (fMRI have revealed that light stimulation of neurons expressing the calcium binding protein parvalbumin (PV is associated with positive blood oxygen level-dependent (BOLD signal in the corresponding barrel field but also with negative BOLD in the surrounding deeper area. Here, we demonstrate that in acute brain slices, ChR2-based photostimulation of PV containing neurons gives rise to an effective contraction of penetrating arterioles. These results support the neurogenic hypothesis of a complex distributed nervous system controlling the CBF.

  18. Dual role of cerebral blood flow in regional brain temperature control in the healthy newborn infant.

    Science.gov (United States)

    Iwata, Sachiko; Tachtsidis, Ilias; Takashima, Sachio; Matsuishi, Toyojiro; Robertson, Nicola J; Iwata, Osuke

    2014-10-01

    Small shifts in brain temperature after hypoxia-ischaemia affect cell viability. The main determinants of brain temperature are cerebral metabolism, which contributes to local heat production, and brain perfusion, which removes heat. However, few studies have addressed the effect of cerebral metabolism and perfusion on regional brain temperature in human neonates because of the lack of non-invasive cot-side monitors. This study aimed (i) to determine non-invasive monitoring tools of cerebral metabolism and perfusion by combining near-infrared spectroscopy and echocardiography, and (ii) to investigate the dependence of brain temperature on cerebral metabolism and perfusion in unsedated newborn infants. Thirty-two healthy newborn infants were recruited. They were studied with cerebral near-infrared spectroscopy, echocardiography, and a zero-heat flux tissue thermometer. A surrogate of cerebral blood flow (CBF) was measured using superior vena cava flow adjusted for cerebral volume (rSVC flow). The tissue oxygenation index, fractional oxygen extraction (FOE), and the cerebral metabolic rate of oxygen relative to rSVC flow (CMRO₂ index) were also estimated. A greater rSVC flow was positively associated with higher brain temperatures, particularly for superficial structures. The CMRO₂ index and rSVC flow were positively coupled. However, brain temperature was independent of FOE and the CMRO₂ index. A cooler ambient temperature was associated with a greater temperature gradient between the scalp surface and the body core. Cerebral oxygen metabolism and perfusion were monitored in newborn infants without using tracers. In these healthy newborn infants, cerebral perfusion and ambient temperature were significant independent variables of brain temperature. CBF has primarily been associated with heat removal from the brain. However, our results suggest that CBF is likely to deliver heat specifically to the superficial brain. Further studies are required to assess the

  19. Blood Flow in the Microcirculation

    Science.gov (United States)

    Secomb, Timothy W.

    2017-01-01

    The microcirculation is an extensive network of microvessels that distributes blood flow throughout living tissues. Reynolds numbers are much less than 1, and the equations of Stokes flow apply. Blood is a suspension of cells with dimensions comparable to microvessel diameters. Highly deformable red blood cells, which transport oxygen, have a volume concentration (hematocrit) of 40–45% in humans. In the narrowest capillaries, these cells move in single file with a surrounding lubricating layer of plasma. In larger vessels, the red blood cells migrate toward the centerline, reducing the resistance to blood flow. Vessel walls are coated with a layer of macromolecules that restricts flow. At diverging bifurcations, hematocrit is not evenly distributed in the downstream vessels. Other particles are driven toward the walls by interactions with red blood cells. These physiologically important phenomena are discussed here from a fluid mechanical perspective.

  20. Humoral Control of Regional Blood Flow in Hemorrhagic Shock in Non-Resuscitated and Resuscitated Animals.

    Science.gov (United States)

    1987-07-17

    to perfusion with autologous normal (non-shock) blood. This increased resistance could be eliminated with phentolamine . However, oxygen consumption...perfusion with normal blood of 2.1 resistance units during perfusion with shock blood (pɘ.001). In a total of 17 phentolamine treated pig limbs...mL/min for normal blood and 1.4 mL/min for shock blood. None of these differences was statistically significant. The findings show that phentolamine

  1. Arterial line pressure control enhanced extracorporeal blood flow prescription in hemodialysis patients

    Directory of Open Access Journals (Sweden)

    Rosales Laura

    2008-11-01

    Full Text Available Abstract Background In hemodialysis, extracorporeal blood flow (Qb recommendation is 300–500 mL/min. To achieve the best Qb, we based our prescription on dynamic arterial line pressure (DALP. Methods This prospective study included 72 patients with catheter Group 1 (G1, 1877 treatments and 35 arterio-venous (AV fistulae Group 2 (G2, 1868 treatments. The dialysis staff was trained to prescribe Qb sufficient to obtain DALP between -200 to -250 mmHg. We measured ionic clearance (IK: mL/min, access recirculation, DALP (mmHg and Qb (mL/min. Six prescription zones were identified: from an optimal A zone (Qb > 400, DALP -200 to -250 to zones with lower Qb E (Qb -199. Results Treatments distribution in A was 695 (37% in G1 vs. 704 (37.7% in G2 (P = 0.7. In B 150 (8% in G1 vs. 458 (24.5% in G2 (P P = 0.62. IK in A was 214 ± 34 (G1 vs. 213 ± 35 (G2 (P = 0.65. IK Anova between G2 zones was: A vs. C and D (P P = 0.02. Conclusion In conclusion, an optimal Qb can de prescribed with DALP of -200 mmHg. Staff adherence to DLAP treatment prescription could be reached up to 81.3% in catheters and 84.1% in AV fistulae.

  2. Endovascular blood flow measurement system

    Science.gov (United States)

    Khe, A. K.; Cherevko, A. A.; Chupakhin, A. P.; Krivoshapkin, A. L.; Orlov, K. Yu

    2016-06-01

    In this paper an endovascular measurement system used for intraoperative cerebral blood flow monitoring is described. The system is based on a Volcano ComboMap Pressure and Flow System extended with analogue-to-digital converter and PC laptop. A series of measurements performed in patients with cerebrovascular pathologies allows us to introduce “velocity-pressure” and “flow rate-energy flow rate” diagrams as important characteristics of the blood flow. The measurement system presented here can be used as an additional instrument in neurosurgery for assessment and monitoring of the operation procedure. Clinical data obtained with the system are used for construction of mathematical models and patient-specific simulations. The monitoring of the blood flow parameters during endovascular interventions was approved by the Ethics Committee at the Meshalkin Novosibirsk Research Institute of Circulation Pathology and included in certain surgical protocols for pre-, intra- and postoperative examinations.

  3. Evidence of low dimensional chaos in renal blood flow control in genetic and experimental hypertension

    Science.gov (United States)

    Yip, K.-P.; Marsh, D. J.; Holstein-Rathlou, N.-H.

    1995-01-01

    We applied a surrogate data technique to test for nonlinear structure in spontaneous fluctuations of hydrostatic pressure in renal tubules of hypertensive rats. Tubular pressure oscillates at 0.03-0.05 Hz in animals with normal blood pressure, but the fluctuations become irregular with chronic hypertension. Using time series from rats with hypertension we produced surrogate data sets to test whether they represent linearly correlated noise or ‘static’ nonlinear transforms of a linear stochastic process. The correlation dimension and the forecasting error were used as discriminating statistics to compare surrogate with experimental data. The results show that the original experimental time series can be distinguished from both linearly and static nonlinearly correlated noise, indicating that the nonlinear behavior is due to the intrinsic dynamics of the system. Together with other evidence this strongly suggests that a low dimensional chaotic attractor governs renal hemodynamics in hypertension. This appears to be the first demonstration of a transition to chaotic dynamics in an integrated physiological control system occurring in association with a pathological condition.

  4. Carbon dioxide and liver blood flow.

    Science.gov (United States)

    Dutton, R; Levitzky, M; Berkman, R

    1976-01-01

    This study was designed to determine blood flow to the liver during hypercapnia and combined hypercapnia-hypoxia with the portal vein and hepatic artery intact except for placement of an electromagnetic flow probe around these vessels. Twenty mongrel dogs weighing 30-45 kg were anesthetized with pentobarbital and flow probes and occluders were surgically implanted. Ten of these dogs were subjected to hypercapnia alone. During inspiration of 6% CO2 in room air, portal vein flow increased from 588 +/- 73 ml/min to 731 +/- 113 ml/min (p less than .05), while hepatic artery flow did not change significantly from its control mean of 221 +/- 38 ml/min. In the remaining dogs, inhalation of 6% O2 resulted in a reduction of portal blood flow within 30 min from 527 +/- 55 ml/min to 381 +/- 41 ml/min (p less than .01). Again, mean hepatic artery flow did not increase significantly above its control of 273 +/- 43 ml/min. Subsequent inhalation of 6% CO2 plus 6% O2 (combined hypercapniahypoxia) for 30 min in these same animals resulted in a significant increase of portal vein blood flow from 514 +/- 46 ml/min to 716 +/- 116 ml/min (p less than .05). Thus, hypercapnia alone increases total liver blood flow, primarily by an increase in portal vein flow. Hypoxia results in a decrease in portal vein flow. The superimposition of hypercapnia on hypoxia restores blood flow to a level close to that found with hypercapnia alone. Hypercapnia in the range of 63 +/- 4 mmHg PCO2 overwhelms the tendency toward a reduction of portal vein blood flow induced by an arterial PO2 of 42 +/- 5 mmHg in the presence of mild hypocapnia (PCO2 : 30.2 +/- 1 mmHg).

  5. Neuromodulation of cerebral blood flow

    NARCIS (Netherlands)

    ter Laan, Mark

    2014-01-01

    Dit proefschrift behandelt de modulatie van de cerebrale doorbloeding (cerebral blood flow, CBF) door cervicale elektrische stimulatie en de aanname dat het sympathisch zenuwstelsel hierin een specifieke rol speelt. Enkele resultaten met cervicale ruggenmergsstimulatie (spinal cord stimulation, SCS)

  6. Chaotic advection in blood flow.

    Science.gov (United States)

    Schelin, A B; Károlyi, Gy; de Moura, A P S; Booth, N A; Grebogi, C

    2009-07-01

    In this paper we argue that the effects of irregular chaotic motion of particles transported by blood can play a major role in the development of serious circulatory diseases. Vessel wall irregularities modify the flow field, changing in a nontrivial way the transport and activation of biochemically active particles. We argue that blood particle transport is often chaotic in realistic physiological conditions. We also argue that this chaotic behavior of the flow has crucial consequences for the dynamics of important processes in the blood, such as the activation of platelets which are involved in the thrombus formation.

  7. Magnetohydrodynamics of blood flow.

    Science.gov (United States)

    Keltner, J R; Roos, M S; Brakeman, P R; Budinger, T F

    1990-10-01

    The changes in hydrostatic pressure and electrical potentials across vessels in the human vasculature in the presence of a large static magnetic field are estimated to determine the feasibility of in vivo NMR spectroscopy at fields as high as 10 T.A 10-T magnetic field changes the vascular pressure in a model of the human vasculature by less than 0.2%. An exact solution to the magnetohydrodynamic equations describing a conducting fluid flowing transverse to a static magnetic field in a nonconducting, straight, circular tube is used. This solution is compared to an approximate solution that assumes that no magnetic fields are induced in the fluid and that has led previous investigators to predict significant biological effects from static magnetic fields. Experimental results show that the exact solution accurately predicts the magnetohydrodynamic slowing of 15% NaCl flowing transverse to 2.3- and 4.7-T magnetic fields for fluxes below 0.5 liter/min while the approximate solution predicts a much more retarded flow.

  8. Cerebral blood-flow tomography

    DEFF Research Database (Denmark)

    Lassen, N A; Henriksen, L; Holm, S;

    1983-01-01

    Tomographic maps of local cerebral blood flow (CBF) were obtained with xenon-133 and with isopropyl-amphetamine-iodine-123 (IMP) in 11 subjects: one normal, two tumor cases, and eight cerebrovascular cases. A highly sensitive four-face, rapidly rotating, single-photon emission tomograph was used......., and with low radiation exposure to patient and personnel. On the other hand, IMP gives an image of slightly higher resolution. It also introduces a new class of iodinated brain-seeking compounds allowing, perhaps, imaging of other functions more important than mere blood flow.......Tomographic maps of local cerebral blood flow (CBF) were obtained with xenon-133 and with isopropyl-amphetamine-iodine-123 (IMP) in 11 subjects: one normal, two tumor cases, and eight cerebrovascular cases. A highly sensitive four-face, rapidly rotating, single-photon emission tomograph was used...

  9. Chronic blood pressure control.

    Science.gov (United States)

    Brands, Michael W

    2012-10-01

    Chronic blood pressure is maintained within very narrow limits around an average value. However, the multitude of physiologic processes that participate in blood pressure control present a bewildering array of possibilities to explain how such tight control of arterial pressure is achieved. Guyton and Coleman and colleagues addressed this challenge by creating a mathematical model that integrated the short- and long-term control systems for overall regulation of the circulation. The hub is the renal-body fluid feedback control system, which links cardiac function and vascular resistance and capacitance with fluid volume homeostasis as the foundation for chronic blood pressure control. The cornerstone of that system is renal sodium excretory capability, which is defined by the direct effect of blood pressure on urinary sodium excretion, that is, "pressure natriuresis." Steady-state blood pressure is the pressure at which pressure natriuresis balances sodium intake over time; therefore, renal sodium excretory capability is the set point for chronic blood pressure. However, this often is misinterpreted as dismissing, or minimizing, the importance of nonrenal mechanisms in chronic blood pressure control. This article explains the renal basis for the blood pressure set point by focusing on the absolute dependence of our survival on the maintenance of sodium balance. Two principal threats to sodium balance are discussed: (1) a change in sodium intake or renal excretory capability and (2) a change in blood pressure. In both instances, circulatory homeostasis is maintained because the sodium balance blood pressure set point is reached.

  10. Cellular transport of l-arginine determines renal medullary blood flow in control rats, but not in diabetic rats despite enhanced cellular uptake capacity.

    Science.gov (United States)

    Persson, Patrik; Fasching, Angelica; Teerlink, Tom; Hansell, Peter; Palm, Fredrik

    2017-02-01

    Diabetes mellitus is associated with decreased nitric oxide bioavailability thereby affecting renal blood flow regulation. Previous reports have demonstrated that cellular uptake of l-arginine is rate limiting for nitric oxide production and that plasma l-arginine concentration is decreased in diabetes. We therefore investigated whether regional renal blood flow regulation is affected by cellular l-arginine uptake in streptozotocin-induced diabetic rats. Rats were anesthetized with thiobutabarbital, and the left kidney was exposed. Total, cortical, and medullary renal blood flow was investigated before and after renal artery infusion of increasing doses of either l-homoarginine to inhibit cellular uptake of l-arginine or N(ω)-nitro- l-arginine methyl ester (l-NAME) to inhibit nitric oxide synthase. l-Homoarginine infusion did not affect total or cortical blood flow in any of the groups, but caused a dose-dependent reduction in medullary blood flow. l-NAME decreased total, cortical and medullary blood flow in both groups. However, the reductions in medullary blood flow in response to both l-homoarginine and l-NAME were more pronounced in the control groups compared with the diabetic groups. Isolated cortical tubular cells displayed similar l-arginine uptake capacity whereas medullary tubular cells isolated from diabetic rats had increased l-arginine uptake capacity. Diabetics had reduced l-arginine concentrations in plasma and medullary tissue but increased l-arginine concentration in cortical tissue. In conclusion, the reduced l-arginine availability in plasma and medullary tissue in diabetes results in reduced nitric oxide-mediated regulation of renal medullary hemodynamics. Cortical blood flow regulation displays less dependency on extracellular l-arginine and the upregulated cortical tissue l-arginine may protect cortical hemodynamics in diabetes.

  11. An implantable blood pressure and flow transmitter.

    Science.gov (United States)

    Rader, R. D.; Meehan, J. P.; Henriksen, J. K. C.

    1973-01-01

    A miniature totally implantable FM/FM telemetry system has been developed to simultaneously measure blood pressure and blood flow, thus providing an appreciation of the hemodynamics of the circulation to the entire body or to a particular organ. Developed for work with animal subjects, the telemetry system's transmission time is controlled by an RF signal that permits an operating life of several months. Pressure is detected by a miniature intravascular transducer and flow is detected by an extravascular interferometric ultrasonic technique. Both pressure and flow are calibrated prior to implanting. The pressure calibration can be checked after the implanting by cannulation; flow calibration can be verified only at the end of the experiment by determining the voltage output from the implanted sensing system as a function of several measured flow rates. The utility of this device has been established by its use in investigating canine renal circulation during exercise, emotional encounters, administration of drugs, and application of accelerative forces.

  12. Vascular inward rectifier K+ channels as external K+ sensors in the control of cerebral blood flow.

    Science.gov (United States)

    Longden, Thomas A; Nelson, Mark T

    2015-04-01

    For decades it has been known that external K(+) ions are rapid and potent vasodilators that increase CBF. Recent studies have implicated the local release of K(+) from astrocytic endfeet-which encase the entirety of the parenchymal vasculature-in the dynamic regulation of local CBF during NVC. It has been proposed that the activation of KIR channels in the vascular wall by external K(+) is a central component of these hyperemic responses; however, a number of significant gaps in our knowledge remain. Here, we explore the concept that vascular KIR channels are the major extracellular K(+) sensors in the control of CBF. We propose that K(+) is an ideal mediator of NVC, and discuss KIR channels as effectors that produce rapid hyperpolarization and robust vasodilation of cerebral arterioles. We provide evidence that KIR channels, of the KIR 2 subtype in particular, are present in both the endothelial and SM cells of parenchymal arterioles and propose that this dual positioning of KIR 2 channels increases the robustness of the vasodilation to external K(+), enables the endothelium to be actively engaged in NVC, and permits electrical signaling through the endothelial syncytium to promote upstream vasodilation to modulate CBF.

  13. Effects of CO2 pneumoperitoneum on blood flow vol-ume of abdominal organs of rabbits with controlled hem-orrhagic shock and liver impact injuries

    Institute of Scientific and Technical Information of China (English)

    ZHANG Lian-yang; ZHAO Song; LI Yong; MA Xiao-lin

    2009-01-01

    Objective: To investigate the effects of CO2 pneumo-peritoneum on blood flow volume of abdominal organs of rabbits with controlled hemorrhagic shock model and liver impact injuries.Methods: After controlled hemorrhagic shock and liver impact injuries, the rabbit model was established. Eighteen rabbits subjected to hemorrhagic shock and liver impact inju-ries were divided into 3 groups randomly according to the volume of lost blood: light hemorrhagic shock (blood loss volume was 10%, 6 ml/kg), moderate hemorrhagic shock (20%, 12 ml/kg) and severe hemorrhagic shock (40%, 22 ml/kg). Intraabdominal pressures of CO2 pneumoperitoneum was 10 mmHg. Color-labeled microspheres were used to mea-sure the blood flow volume of the liver, kidney and stomach before pneumoperitoneum at 30 minutes and 2 hours after pneumoperitoneum and 30 minutes after deflation. And the mortality and hepatic traumatic condition of rabbits were recorded.Results: Of the 18 rabbits, there were 9 with liver impact injuries at Grade Ⅰ, 8 at Grade Ⅱ and Ⅰ at Grade Ⅲ (according to AIS-2005). The mortality rate in light hemorrhagic shock group was 33.33%, and that in moderate or severe hemor-rhagic shock group was 100% within 30 minutes and 2 hours after pneumoperitoneum, respectively. The blood flow vol-ume in the organs detected decreased at 30 minutes under pneumoperitoneum in light and moderate hemorrhagic shock groups. At the same time, the blood flow volume of the liver in moderate hemorrhagic shock group decreased more sig-nificantly than that in light hemorrhagic shock group.Conclusions: The blood flow volume of abdominal organs in rabbits is decreased obviously under CO2 pneumoperitoneum, with fairly high mortality rate. It is be-lieved that CO2 pneumoperitoneum should cautiously be used in abdominal injury accompanied with hemorrhagic shock, especially under non-resuscitation conditions.

  14. Capillary pericytes regulate cerebral blood flow in health and disease

    DEFF Research Database (Denmark)

    Hall, Catherine N; Reynell, Clare; Gesslein, Bodil;

    2014-01-01

    Increases in brain blood flow, evoked by neuronal activity, power neural computation and form the basis of BOLD (blood-oxygen-level-dependent) functional imaging. Whether blood flow is controlled solely by arteriole smooth muscle, or also by capillary pericytes, is controversial. We demonstrate...... blood flow, capillaries dilate before arterioles and are estimated to produce 84% of the blood flow increase. In pathology, ischaemia evokes capillary constriction by pericytes. We show that this is followed by pericyte death in rigor, which may irreversibly constrict capillaries and damage the blood......-brain barrier. Thus, pericytes are major regulators of cerebral blood flow and initiators of functional imaging signals. Prevention of pericyte constriction and death may reduce the long-lasting blood flow decrease that damages neurons after stroke....

  15. Ocular Blood Flow Autoregulation Mechanisms and Methods

    Directory of Open Access Journals (Sweden)

    Xue Luo

    2015-01-01

    Full Text Available The main function of ocular blood flow is to supply sufficient oxygen and nutrients to the eye. Local blood vessels resistance regulates overall blood distribution to the eye and can vary rapidly over time depending on ocular need. Under normal conditions, the relation between blood flow and perfusion pressure in the eye is autoregulated. Basically, autoregulation is a capacity to maintain a relatively constant level of blood flow in the presence of changes in ocular perfusion pressure and varied metabolic demand. In addition, ocular blood flow dysregulation has been demonstrated as an independent risk factor to many ocular diseases. For instance, ocular perfusion pressure plays key role in the progression of retinopathy such as glaucoma and diabetic retinopathy. In this review, different direct and indirect techniques to measure ocular blood flow and the effect of myogenic and neurogenic mechanisms on ocular blood flow are discussed. Moreover, ocular blood flow regulation in ocular disease will be described.

  16. Ocular Blood Flow Autoregulation Mechanisms and Methods

    OpenAIRE

    Xue Luo; Yu-meng Shen; Meng-nan Jiang; Xiang-feng Lou; Yin Shen

    2015-01-01

    The main function of ocular blood flow is to supply sufficient oxygen and nutrients to the eye. Local blood vessels resistance regulates overall blood distribution to the eye and can vary rapidly over time depending on ocular need. Under normal conditions, the relation between blood flow and perfusion pressure in the eye is autoregulated. Basically, autoregulation is a capacity to maintain a relatively constant level of blood flow in the presence of changes in ocular perfusion pressure and va...

  17. Angiotensin II and renal prostaglandin release in the dog. Interactions in controlling renal blood flow and glomerular filtration rate.

    Science.gov (United States)

    Bugge, J F; Stokke, E S

    1994-04-01

    The relationship between angiotensin II and renal prostaglandins, and their interactions in controlling renal blood flow (RBF) and glomerular filtration rate (GFR) were investigated in 18 anaesthetized dogs with acutely denervated kidneys. Intrarenal angiotensin II infusion increased renal PGE2 release (veno-arterial concentration difference times renal plasma flow) from 1.7 +/- 0.9 to 9.1 +/- 0.4 and 6-keto-PGF1 alpha release from 0.1 +/- 0.1 to 5.3 +/- 2.1 pmol min-1. An angiotensin II induced reduction in RBF of 20% did not measurably change GFR whereas a 30% reduction reduced GFR by 18 +/- 8%. Blockade of prostaglandin synthesis approximately doubled the vasoconstrictory action of angiotensin II, and all reductions in RBF were accompanied by parallel reductions in GFR. When prostaglandin release was stimulated by infusion of arachidonic acid (46.8 +/- 13.3 and 15.9 +/- 5.4 pmol min-1 for PGE2, and 6-keto-PGF1 alpha, respectively), angiotensin II did not change prostaglandin release, but had similar effects on the relationship between RBF and GFR as during control. In an ureteral occlusion model with stopped glomerular filtration measurements of ureteral pressure and intrarenal venous pressure permitted calculations of afferent and efferent vascular resistances. Until RBF was reduced by 25-30% angiotensin II increased both afferent and efferent resistances almost equally, keeping the ureteral pressure constant. At greater reductions in RBF, afferent resistance increased more than the efferent leading to reductions in ureteral pressure. This pattern was not changed by blockade of prostaglandin synthesis indicating no influence of prostaglandins on the distribution of afferent and efferent vascular resistances during angiotensin II infusion. In this ureteral occlusion model glomerular effects of angiotensin II will not be detected, and it might well be that the shift from an effect predominantly on RBF to a combined effect on both RBF and GFR induced by inhibition

  18. EFFECT OF INCREASED WHOLE-BLOOD VISCOSITY ON REGIONAL BLOOD FLOWS IN CHRONICALLY HYPOXEMIC LAMBS

    NARCIS (Netherlands)

    DALINGHAUS, M; KNOESTER, H; GRATAMA, JWC; VANDERMEER, J; ZIJLSTRA, WG; KUIPERS, JRG

    1994-01-01

    In chronic hypoxemia blood flow and oxygen supply to vital organs are maintained, but to nonvital organs they are decreased. We measured organ blood flows (microspheres) and whole blood viscosity in 10 chronically hypoxemic lambs, with an atrial septal defect and pulmonary stenosis, and in 8 control

  19. Automated postoperative blood pressure control

    Institute of Scientific and Technical Information of China (English)

    Hang ZHENG; Kuanyi ZHU

    2005-01-01

    It is very important to maintain the level of mean arterial pressure (MAP).The MAP control is applied in many clinical situations,including limiting bleeding during cardiac surgery and promoting healing for patient's post-surgery.This paper presents a fuzzy controller-based multiple-model adaptive control system for postoperative blood pressure management.Multiple-model adaptive control (MMAC) algorithm is used to identify the patient model,and it is a feasible system identification method even in the presence of large noise.Fuzzy control (FC) method is used to design controller bank.Each fuzzy controller in the controller bank is in fact a nonlinear proportional-integral (PI) controller,whose proportional gain and integral gain are adjusted continuously according to error and rate of change of error of the plant output,resulting in better dynamic and stable control performance than the regular PI controller,especially when a nonlinear process is involved.For demonstration,a nonlinear,pulsatile-flow patient model is used for simulation,and the results show that the adaptive control system can effectively handle the changes in patient's dynamics and provide satisfactory performance in regulation of blood pressure of hypertension patients.

  20. Dexmedetomidine decreases the oral mucosal blood flow.

    Science.gov (United States)

    Kawaai, Hiroyoshi; Yoshida, Kenji; Tanaka, Eri; Togami, Kohei; Tada, Hitoshi; Ganzberg, Steven; Yamazaki, Shinya

    2013-12-01

    There is an abundance of blood vessels in the oral cavity, and intraoperative bleeding can disrupt operations. There have been some interesting reports about constriction of vessels in the oral cavity, one of which reported that gingival blood flow in cats is controlled by sympathetic α-adrenergic fibres that are involved with vasoconstriction. Dexmedetomidine is a sedative and analgesic agent that acts through the α-2 adrenoceptor, and is expected to have a vasoconstrictive action in the oral cavity. We have focused on the relation between the effects of α-adrenoceptors by dexmedetomidine and vasoconstriction in oral tissues, and assessed the oral mucosal blood flow during sedation with dexmedetomidine. The subjects comprised 13 healthy male volunteers, sedated with dexmedetomidine in a loading dose of 6 μg/kg/h for 10 min and a continuous infusion of 0.7 μg/kg/h for 32 min. The mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), stroke volume (SV), systemic vascular resistance (SVR), and palatal mucosal blood flow (PMBF) were measured at 0, 5, 10, 12, 22, and 32 min after the start of the infusion. The HR, CO, and PBMF decreased significantly during the infusion even though there were no differences in the SV. The SVR increased significantly but the PMBF decreased significantly. In conclusion, PMBF was reduced by the mediating effect of dexmedetomidine on α-2 adrenoceptors.

  1. Dynamic power flow controllers

    Science.gov (United States)

    Divan, Deepakraj M.; Prasai, Anish

    2017-03-07

    Dynamic power flow controllers are provided. A dynamic power flow controller may comprise a transformer and a power converter. The power converter is subject to low voltage stresses and not floated at line voltage. In addition, the power converter is rated at a fraction of the total power controlled. A dynamic power flow controller controls both the real and the reactive power flow between two AC sources having the same frequency. A dynamic power flow controller inserts a voltage with controllable magnitude and phase between two AC sources; thereby effecting control of active and reactive power flows between two AC sources.

  2. Cerebellar blood flow in methylmercury poisoning (Minamata disease)

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, K.; Korogi, Y.; Tomiguchi, S.; Takahashi, M. [Dept. of Radiology, Kumamoto University School of Medicine (Japan); Okajima, T. [Dept. of Neurology, Johnan Hospital, Maihara, Johnan-mochi (Japan); Sato, H. [Dept. of Neurology, Minamata City General Hospital and Medical Centre (Japan)

    2001-04-01

    We looked at regional cerebellar blood flow in patients with Minamata disease (MD) using technetium-99 m ethyl cysteinate dimer (99m-Tc-ECD). We carried out single-photon emission computed tomography (SPECT) on 15 patients with MD (eight men, seven women, aged 51-78 years, mean 70.5 years) and 11 control subjects (eight men, three women, aged 62-80 years, mean 72.5 years). Regional blood flow was measured in the superior, middle, and inferior portions of the cerebellar hemispheres, and the frontal, temporal and occipital cerebral lobes. The degree of cerebellar atrophy was assessed on MRI. There were significant differences in regional blood flow in all parts of the cerebellum between patients and control, but no significant decrease was observed in the cerebrum. Blood flow was lower in the inferior cerebellum than in the other parts. Even in patients without cerebellar atrophy, flow was significantly decreased regional blood flow in the inferior part. (orig.)

  3. Cerebellar blood flow in methylmercury poisoning (Minamata disease).

    Science.gov (United States)

    Itoh, K; Korogi, Y; Tomiguchi, S; Takahashi, M; Okajima, T; Sato, H

    2001-04-01

    We looked at regional cerebellar blood flow in patients with Minamata disease (MD) using technetium-99m ethyl cysteinate dimer (99m-Tc-ECD). We carried out single-photon emission computed tomography (SPECT) on 15 patients with MD (eight men, seven women, aged 51-78 years, mean 70.5 years) and 11 control subjects (eight men, three women, aged 62-80 years, mean 72.5 years). Regional blood flow was measured in the superior, middle, and inferior portions of the cerebellar hemispheres, and the frontal, temporal and occipital cerebral lobes. The degree of cerebellar atrophy was assessed on MRI. There were significant differences in regional blood flow in all parts of the cerebellum between patients and control, but no significant decrease was observed in the cerebrum. Blood flow was lower in the inferior cerebellum than in the other parts. Even in patients without cerebellar atrophy, flow was significantly decreased regional blood flow in the inferior part.

  4. Quantitative Cerebral Blood Flow Measurements Using MRI

    OpenAIRE

    Muir, Eric R; Watts, Lora Talley; Tiwari, Yash Vardhan; Bresnen, Andrew; Timothy Q Duong

    2014-01-01

    Magnetic resonance imaging utilized as a quantitative and noninvasive method to image cerebral blood flow. The two most common techniques used to detect cerebral blood flow are dynamic susceptibility contrast (DSC) perfusion MRI and arterial spin labeling perfusion MRI. Herein we describe the use of these two techniques to measure cerebral blood flow in rodents, including methods, analysis, and important considerations when utilizing these techniques.

  5. Neural and non-neural control of skin blood flow during isometric handgrip exercise in the heat stressed human

    DEFF Research Database (Denmark)

    Shibasaki, M.; Rasmussen, P.; Secher, Niels H.

    2009-01-01

    During heat stress, isometric handgrip (IHG) exercise causes cutaneous vasoconstriction, but it remains controversial whether neural mechanisms are responsible for this observation. The objective of this study was to test the hypothesis that cutaneous vasoconstriction during IHG exercise in heat ...... = 0.01). These findings suggest that neural and non-neural mechanisms contribute to the reduction in forearm CVC during IHG exercise in heat stressed humans Udgivelsesdato: 2009/5/1......During heat stress, isometric handgrip (IHG) exercise causes cutaneous vasoconstriction, but it remains controversial whether neural mechanisms are responsible for this observation. The objective of this study was to test the hypothesis that cutaneous vasoconstriction during IHG exercise in heat...... stressed individuals occurs via a neural mechanism. An axillary nerve blockade was performed to block efferent nerve traffic to the left forearm in seven healthy subjects. Two intradermal microdialysis probes were placed within forearm skin of the blocked area. Forearm skin blood flow was measured by laser...

  6. Sympathetic reflex control of skeletal muscle blood flow in patients with congestive heart failure: evidence for beta-adrenergic circulatory control

    Energy Technology Data Exchange (ETDEWEB)

    Kassis, E.; Jacobsen, T.N.; Mogensen, F.; Amtorp, O.

    1986-11-01

    Mechanisms controlling forearm muscle vascular resistance (FMVR) during postural changes were investigated in seven patients with severe congestive heart failure (CHF) and in seven control subjects with unimpaired left ventricular function. Relative brachioradial muscle blood flow was determined by the local /sup 133/Xe-washout technique. Unloading of baroreceptors with use of 45 degree upright tilt was comparably obtained in the patients with CHF and control subjects. Control subjects had substantially increased FMVR and heart rate to maintain arterial pressure whereas patients with CHF had decreased FMVR by 51 +/- 11% and had no increase in heart rate despite a fall in arterial pressure during upright tilt. The autoregulatory and local vasoconstrictor reflex responsiveness during postural changes in forearm vascular pressures were intact in both groups. In the patients with CHF, the left axillary nerve plexus was blocked by local anesthesia. No alterations in forearm vascular pressures were observed. This blockade preserved the local regulation of FMVR but reversed the vasodilator response to upright tilt as FMVR increased by 30 +/- 7% (p less than .02). Blockade of central neural impulses to this limb combined with brachial arterial infusions of phentolamine completely abolished the humoral vasoconstriction in the tilted position. Infusions of propranolol to the contralateral brachial artery that did not affect baseline values of heart rate, arterial pressure, or the local reflex regulation of FMVR reversed the abnormal vasodilator response to upright tilt as FMVR increased by 42 +/- 12% (p less than .02). Despite augmented baseline values, forearm venous but not arterial plasma levels of epinephrine increased in the tilted position, as did arteri rather than venous plasma concentrations of norepinephrine in these patients.

  7. Distributed Power Flow Controller

    NARCIS (Netherlands)

    Yuan, Z.

    2010-01-01

    In modern power systems, there is a great demand to control the power flow actively. Power flow controlling devices (PFCDs) are required for such purpose, because the power flow over the lines is the nature result of the impedance of each line. Due to the control capabilities of different types of P

  8. Pancreatic islet blood flow and its measurement.

    Science.gov (United States)

    Jansson, Leif; Barbu, Andreea; Bodin, Birgitta; Drott, Carl Johan; Espes, Daniel; Gao, Xiang; Grapensparr, Liza; Källskog, Örjan; Lau, Joey; Liljebäck, Hanna; Palm, Fredrik; Quach, My; Sandberg, Monica; Strömberg, Victoria; Ullsten, Sara; Carlsson, Per-Ola

    2016-05-01

    Pancreatic islets are richly vascularized, and islet blood vessels are uniquely adapted to maintain and support the internal milieu of the islets favoring normal endocrine function. Islet blood flow is normally very high compared with that to the exocrine pancreas and is autonomously regulated through complex interactions between the nervous system, metabolites from insulin secreting β-cells, endothelium-derived mediators, and hormones. The islet blood flow is normally coupled to the needs for insulin release and is usually disturbed during glucose intolerance and overt diabetes. The present review provides a brief background on islet vascular function and especially focuses on available techniques to measure islet blood perfusion. The gold standard for islet blood flow measurements in experimental animals is the microsphere technique, and its advantages and disadvantages will be discussed. In humans there are still no methods to measure islet blood flow selectively, but new developments in radiological techniques hold great hopes for the future.

  9. Bone blood flow and metabolism in humans

    DEFF Research Database (Denmark)

    Heinonen, Ilkka; Kemppainen, Jukka; Kaskinoro, Kimmo;

    2012-01-01

    Human bone blood flow and metabolism during physical exercise remains poorly characterised. In the present study we measured femoral bone blood flow and glucose uptake in young healthy subjects by positron emission tomography in three separate protocols. In six women, blood flow was measured...... in femoral bone at rest and during one leg intermittent isometric exercise with increasing exercise intensities. In nine men, blood flow in femur was determined at rest and during dynamic one leg exercise, and two other physiological perturbations: moderate systemic hypoxia (14 O(2) ) at rest and during...... exercise, and during intra-femoral infusion of high-dose adenosine. Bone glucose uptake was measured at rest and during dynamic one leg exercise in five men. The results indicate that isometric exercise increased femoral bone blood flow from rest (1.8 ± 0.6 ml/100g/min) to low intensity exercise (4.1 ± 1...

  10. The Physics of Coronary Blood Flow

    CERN Document Server

    Zamir, M

    2005-01-01

    Coronary blood flow is blood flow to the heart for its own metabolic needs. In the most common form of heart disease there is a disruption in this flow because of obstructive disease in the vessels that carry the flow. The subject of coronary blood flow is therefore associated mostly with the pathophysiology of this disease, rarely with dynamics or physics. Yet, the system responsible for coronary blood flow, namely the "coronary circulation," is a highly sophisticated dynamical system in which the dynamics and physics of the flow are as important as the integrity of the conducting vessels. While an obstruction in the conducting vessels is a fairly obvious and clearly visible cause of disruption in coronary blood flow, any discord in the complex dynamics of the system can cause an equally grave, though less conspicuous, disruption in the flow. This book is devoted specifically to the dynamics and physics of coronary blood flow. While relevance to the clinical and pathophysiological issues is clearly maintaine...

  11. Mechanics of blood flow in the microcirculation.

    Science.gov (United States)

    Secomb, T W

    1995-01-01

    The microcirculation in most tissues consists of an intricate network of very narrow tubes. In analyses of blood flow through the microcirculation, inertial effects can be neglected, but continuum models for blood cannot be assumed, since blood is a concentrated suspension of cells with dimensions comparable to vessel diameters. These cells strongly influence blood flow. About 45% of blood volume consists of red blood cells, whose key mechanical properties are known. A red cell has a fluid interior, surrounded by a flexible membrane, which strongly resists area changes, but bends and shears easily. White blood cells are comparable in size but much less numerous. They are less flexible than red cells and capable of active locomotion. Other suspended elements are much smaller than red cells: This review focuses on the mechanics of red cell motion in the microcirculation. Experimental and theoretical studies of blood flow in uniform tubes, bifurcations and networks are discussed. Comparisons between predicted and observed flows in networks imply that resistance to blood flow in living microvessels is higher than that in uniform tubes with corresponding diameters. Living microvessels have non-uniform geometries, and red cells must deform continually to traverse them. Theoretical results are presented implying that these transient deformations contribute to increased flow resistance in the microcirculation.

  12. Blood flow autoregulation in pedicled flaps

    DEFF Research Database (Denmark)

    Bonde, Christian T; Holstein-Rathlou, Niels-Henrik; Elberg, Jens J

    2009-01-01

    INTRODUCTION: Clinical work on the blood perfusion in skin and muscle flaps has suggested that some degree of blood flow autoregulation exists in such flaps. An autoregulatory mechanism would enable the flap to protect itself from changes in the perfusion pressure. The purpose of the present study...... was to evaluate if, and to what extent, a tissue flap could compensate a reduction in blood flow due to an acute constriction of the feed artery. Further, we wanted to examine the possible role of smooth muscle L-type calcium channels in the autoregulatory mechanism by pharmacological intervention with the L......-type calcium channel blocker nimodipine and the vasodilator papaverine. MATERIAL AND METHODS: Pedicled flaps were raised in pigs. Flow in the pedicle was reduced by constriction of the feed artery (n=34). A transit time flow probe measured the effect on blood flow continuously. Following this, three different...

  13. Angularis oculi vein blood flow modulates the magnitude but not the control of selective brain cooling in sheep.

    Science.gov (United States)

    Fuller, Andrea; Hetem, Robyn S; Meyer, Leith C R; Maloney, Shane K

    2011-06-01

    To investigate the role of the angularis oculi vein (AOV) in selective brain cooling (SBC), we measured brain and carotid blood temperatures in six adult female Dorper sheep. Halfway through the study, a section of the AOV, just caudal to its junction with the dorsal nasal vein, was extirpated on both sides. Before and after AOV surgery, the sheep were housed outdoors at 21-22°C and were exposed in a climatic chamber to daytime heat (40°C) and water deprivation for 5 days. In sheep outdoors, SBC was significantly lower after the AOV had been cut, with its 24-h mean reduced from 0.25 to 0.01°C (t(5) = 3.06, P = 0.03). Carotid blood temperature also was lower (by 0.28°C) at all times of day (t(5) = 3.68, P = 0.01), but the pattern of brain temperature was unchanged. The mean threshold temperature for SBC was not different before (38.85 ± 0.28°C) and after (38.85 ± 0.39°C) AOV surgery (t(5) =0.00, P = 1.00), but above the threshold, SBC magnitude was about twofold less after surgery. SBC after AOV surgery also was less during heat exposure and water deprivation. However, SBC increased progressively by the same magnitude (0.4°C) over the period of water deprivation, and return of drinking water led to rapid cessation of SBC in sheep before and after AOV surgery. We conclude that the AOV is not the only conduit for venous drainage contributing to SBC in sheep and that, contrary to widely held opinion, control of SBC does not involve changes in the vasomotor state of the AOV.

  14. The effect of hyperosmotic solutions on the hepatic blood flow

    DEFF Research Database (Denmark)

    Winkler, K; Henriksen, Jens Henrik; Tygstrup, N

    1993-01-01

    The present study was undertaken in order to measure the effect of hyperosmotic solutions on portal and hepatic blood flow. In five anaesthetized pigs without arterial blood supply to the liver, portal blood flow rate was measured (electromagnetic flowmeter) during 5 min lasting intravenous...... infusions of hyperosmotic galactose (50%, 84-100 ml) and mannitol (25%, 100 ml), with physiological saline (100 ml) as control. Portal blood flow increased to a peak value of (39% [P = 0.06] galactose and 37%, [P = 0.06], mannitol) soon after stop of the hyperosmotic infusion. For galactose the change ended...... somewhat earlier than for mannitol. Saline induced a minor increase (15%). Similarly, increments of, on average, 144% of the hepatic blood flow rate was seen in six patients with cirrhosis, following infusion of hyperosmotic galactose, the increase being more pronounced than in the pigs. The causes...

  15. Frequency encoding in renal blood flow regulation

    DEFF Research Database (Denmark)

    Marsh, Donald J; Sosnovtseva, Olga; Pavlov, Alexey N;

    2005-01-01

    With a model of renal blood flow regulation, we examined consequences of tubuloglomerular feedback (TGF) coupling to the myogenic mechanism via voltage-gated Ca channels. The model reproduces the characteristic oscillations of the two mechanisms and predicts frequency and amplitude modulation...... of the myogenic oscillation by TGF. Analysis by wavelet transforms of single-nephron blood flow confirms that both amplitude and frequency of the myogenic oscillation are modulated by TGF. We developed a double-wavelet transform technique to estimate modulation frequency. Median value of the ratio of modulation...... TGF cycle to the next. We used a blood pressure signal recorded by telemetry from a conscious rat as the input to the model. Blood pressure fluctuations induced variability in the modulation records similar to those found in the nephron blood flow results. Frequency and amplitude modulation can...

  16. Regulation of blood flow by prostaglandins

    DEFF Research Database (Denmark)

    Boushel, Robert Christopher; Langberg, H; Risum, N;

    2004-01-01

    adaptation of connective tissues e.g. tendon. This review covers the role of PG for mediating tissue blood flow at rest and during increases in metabolic demand such as exercise and reactive hyperaemia. There is strong evidence that PGs contribute to elevate blood flow at rest and during reactive hyperaemia...... in a variety of tissues. Their role for regulating the large increases in muscle blood flow during exercise is less clear which may be explained by redundant mechanisms. Several interactions are known to exist between specific vasodilator substances, and therefore PGs can act in synergy with other substances...... and contribute to functional hyperaemia. Furthermore, there is evidence for differential, tissue-specific influences of PGs where their influence on blood flow during exercise may be profound....

  17. Blood flow and permeability in microvessels

    Science.gov (United States)

    Sugihara-Seki, Masako; Fu, Bingmei M.

    2005-07-01

    The mechanics of blood flow in microvessels and microvessel permeability are reviewed. In the first part, characteristics of blood flow in vivo and in vitro are described from a fluid-mechanical point of view, and mathematical models for blood flow in microvessels are presented. Possible causes of the increased flow resistance obtained in vivo compared to in vitro are examined, including the effects of irregularities of vessel lumen, the presence of endothelial surface glycocalyx and white blood cells. In the second part, the ultrastructural pathways and mechanisms whereby endothelial cells and the clefts between the cells modulate microvessel permeability to water and solutes are introduced. Previous and current models for microvessel permeability to water and solutes are reviewed. These models examine the role of structural components of interendothelial cleft, such as junction strands and surface glycocalyx, in the determination of water and solute transport across the microvessel walls. Transport models in the tissue space surrounding the microvessel are also described.

  18. Controlling your high blood pressure

    Science.gov (United States)

    ... medlineplus.gov/ency/patientinstructions/000101.htm Controlling your high blood pressure To use the sharing features on this page, ... JavaScript. Hypertension is another term used to describe high blood pressure. High blood pressure can lead to: Stroke Heart ...

  19. Cerebral blood flow response to propranolol in streptozotocin diabetic rats

    DEFF Research Database (Denmark)

    Lass, Preben; Knudsen, G M

    1990-01-01

    The influence of propranolol on cerebral blood flow (CBF) was tested in streptozotocin diabetic rats and in control animals. Resting CBF values were 40% lower in the diabetic rats compared with controls. Intravenous injection of propranolol (2 mg kg-1) decreased CBF significantly in the control...

  20. Spontaneous oscillations of capillary blood flow in artificial microvascular networks.

    Science.gov (United States)

    Forouzan, Omid; Yang, Xiaoxi; Sosa, Jose M; Burns, Jennie M; Shevkoplyas, Sergey S

    2012-09-01

    Previous computational studies have suggested that the capillary blood flow oscillations frequently observed in vivo can originate spontaneously from the non-linear rheological properties of blood, without any regulatory input. Testing this hypothesis definitively in experiments involving real microvasculature has been difficult because in vivo the blood flow in capillaries is always actively controlled by the host. The objective of this study was to test the hypothesis experimentally and to investigate the relative contribution of different blood cells to the capillary blood flow dynamics under static boundary conditions and in complete isolation from the active regulatory mechanisms mediated by the blood vessels in vivo. To accomplish this objective, we passed whole blood and re-constituted blood samples (purified red blood cells suspended in buffer or in autologous plasma) through an artificial microvascular network (AMVN) comprising completely inert, microfabricated vessels with the architecture inspired by the real microvasculature. We found that the flow of blood in capillaries of the AMVN indeed oscillates with characteristic frequencies in the range of 0-0.6 Hz, which is in a very good agreement with previous computational studies and in vivo observations. We also found that the traffic of leukocytes through the network (typically neglected in computational modeling) plays an important role in generating the oscillations. This study represents the key piece of experimental evidence in support of the hypothesis that spontaneous, self-sustained oscillations of capillary blood flow can be generated solely by the non-linear rheological properties of blood flowing through microvascular networks, and provides an insight into the mechanism of this fundamentally important microcirculatory phenomenon.

  1. 21 CFR 870.2120 - Extravascular blood flow probe.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Extravascular blood flow probe. 870.2120 Section... blood flow probe. (a) Identification. An extravascular blood flow probe is an extravascular ultrasonic or electromagnetic probe used in conjunction with a blood flowmeter to measure blood flow in...

  2. Cerebral blood flow response to functional activation

    DEFF Research Database (Denmark)

    Paulson, Olaf B; Hasselbalch, Steen G; Rostrup, Egill

    2010-01-01

    Cerebral blood flow (CBF) and cerebral metabolic rate are normally coupled, that is an increase in metabolic demand will lead to an increase in flow. However, during functional activation, CBF and glucose metabolism remain coupled as they increase in proportion, whereas oxygen metabolism only...

  3. Aortic blood flow subtraction: an alternative method for measuring total renal blood flow in conscious dogs

    DEFF Research Database (Denmark)

    Sandgaard, N C F; Andersen, J L; Holstein-Rathlou, N-H;

    2002-01-01

    We have measured total renal blood flow (TRBF) as the difference between signals from ultrasound flow probes implanted around the aorta above and below the renal arteries. The repeatability of the method was investigated by repeated, continuous infusions of angiotensin II and endothelin-1 seven...... arterial blood pressure by 49% and decreased TRBF by 12%, providing an increase in renal vascular resistance of 69%. Dynamic analysis showed autoregulation of renal blood flow in the frequency range ... of TRBF by aortic blood flow subtraction is a practical and reliable method that allows direct comparison of excretory function and renal blood flow from two kidneys. The method also allows direct comparison between TRBF and flow in the caudal aorta....

  4. BLOOD FLOW AND MACROMOLECULAR TRANSPORT IN CURVED BLOOD VESSELS

    Institute of Scientific and Technical Information of China (English)

    WEI Lan; WEN Gong-bi; TAN Wen-chang

    2006-01-01

    A numerical analysis of the steady/pulsatile flow and macromolecular (such as LDL and Albumin) transport in curved blood vessels was carried out. The computational results predict that the vortex of the secondary flow is time-dependent in the aortic arch.The concentration of macromolecule concentrates at the region of sharp curve, and the wall concentration at the outer part is higher than that at the inner part. Atherosclerosis and thrombosis are prone to develop in such regions with sharp flow.

  5. Hepatic and intestinal blood flow following thermal injury

    Energy Technology Data Exchange (ETDEWEB)

    Carter, E.A.; Tompkins, R.G.; Burke, J.F.

    1988-07-01

    Because cardiac output decreases after burn injuries, investigators have assumed, based upon dye clearance techniques, that hepatic and intestinal blood flow are also decreased following these injuries. Blood flow to the liver, stomach, small intestine, and kidney was determined by the uptake of 201thallium and 125I-labeled fatty acid (para-125I-phenyl-3-methyl pentanoic acid) in a 20% body surface area scald injury that also included plasma volume replacement resuscitation. Uptake of these radioisotopes was determined 15 minutes, 18 hours, and 72 hours after injury. The uptake of the 201thallium and 125I-labeled fatty acid by the gastrointestinal tissues was not statistically different at any of the time periods after comparison of the injured and control (sham-treated) animals. 201Thallium uptake by the kidney was significantly diminished 15 minutes after the burn injury (P less than 0.01). Based on these blood flow measurement techniques, the data suggest that the 20% body surface area scald injury did not alter blood flow to the liver or gastrointestinal tract within the initial 72 hours after the burn injury even though a decrease in renal blood flow was easily detected. These results suggest that the dysfunction of the gastrointestinal system or hepatic system observed after an acute burn injury is not simply the result of hypovolemic shock, which reduces both renal and mesenteric blood flow. These gastrointestinal and hepatic alterations may be related to a factor or factors other than intestinal ischemia.

  6. Salt-gland secretion and blood flow in the goose.

    Science.gov (United States)

    Hanwell, A; Linzell, J L; Peaker, M

    1971-03-01

    1. Salt-gland blood flow in the domestic goose has been measured using a combination of Sapirstein's indicator fractionation technique for organ blood flow and Fegler's thermodilution method for cardiac output.2. Nasal salt secretion was induced by giving 0.5 M-NaCl or 0.154 M-NaCl I.V. or by giving artificial sea water by stomach tube into the proventriculus.3. During secretion, salt-gland blood flow increased from 82.7 +/- 21.9 ml./100 g tissue. min to as high as 2179 ml./100 g. min (mean 1209 +/- 140).4. The rate of secretion in response to salt loading was very variable and was not correlated with the rate of blood flow.5. From the data obtained, it could be calculated that the median values for the percentage extraction of ions from the arterial plasma were Na 15%, K 35%, Cl 21% and water 5.8%.6. Atropine abolished secretion but not the increase in blood flow produced by salt loading.7. Unilateral complete denervation abolished secretion from and the increase in blood flow through the operated but not the control gland.8. Anaesthesia, induced by pentobarbitone sodium, almost completely blocked secretion and the increase in blood flow in the salt-gland in response to salt loading.9. In geese given 0.5 or 0.154 M-NaCl I.V. a positive, significant correlation was found between the total amount of nasal secretion collected over 30 min and the concentrations of Na and Cl in the nasal fluid. However, when the time course of secretion was followed in any one bird, the rate of secretion was inversely related to the concentrations of Na and Cl.10. Harderian gland blood flow was not affected by salt loading.

  7. Assessment of intramural blood flow and neurogenic control in intact and hypertrophic urinary bladder with harmonic analysis of bioimpedance in rats.

    Science.gov (United States)

    Kirpatovsky, V I; Mudraya, I S; Revenko, S V; Nesterov, A V; Gavrilov, I Yu; Khromov, R A; Bablumyan, A Yu

    2012-08-01

    High-resolution impedancometry and harmonic (Fourier) analysis of variable component of bioimpedance revealed rhythmic oscillations of urinary bladder bioimpedance at the Mayer wave, respiration, and heartbeat frequencies. The power values of the corresponding Mayer, respiratory, and cardiac peaks were calculated to assess circulation in the urinary bladder wall and its autonomic nervous control at various stages of infusion cystometry in intact rats and in the rats with preliminary formed infravesical obstruction (IVO). In intact rats, filling of the bladder with physiological saline diminished the power of the first (fundamental) cardiac peak attesting to a decrease of the blood flow in the bladder wall. Simultaneously, the power of low-frequency Mayer peak reflecting sympathetic activity increased, while the power of respiratory peak decreased supposedly reflecting abatement of the parasympathetic influences. Bladder voiding was accompanied by a decrease of Mayer peak and increase of the respiratory one. Prior to infusion cystometry, the intravesical pressure in IVO rats was elevated while the power of fundamental cardiac peak was below the control value. Filling the bladder in these rats was accompanied by further decrease of the cardiac peak reflecting still greater drop in blood supply. In control rats, voiding the bladder normalized the vesical circulation assessed by the cardiac peak, while in IVO rats this peak remained decreased. The reciprocal changes of Mayer and respiratory peaks observed during infusion cystometry in the norm were replaced by unidirectional decrease in the power of both peaks in IVO rats, which probably attest to disturbance of autonomic nervous control in the hypertrophic urinary bladder in these rats.

  8. A multiple disk centrifugal pump as a blood flow device.

    Science.gov (United States)

    Miller, G E; Etter, B D; Dorsi, J M

    1990-02-01

    A multiple disk, shear force, valveless centrifugal pump was studied to determine its suitability as a blood flow device. A pulsatile version of the Tesla viscous flow turbine was designed by modifying the original steady flow pump concept to produce physiological pressures and flows with the aid of controlling circuitry. Pressures and flows from this pump were compared to a Harvard Apparatus pulsatile piston pump. Both pumps were connected to an artificial circulatory system. Frequency and systolic duration were varied over a range of physiological conditions for both pumps. The results indicated that the Tesla pump, operating in a pulsatile mode, is capable of producing physiologic pressures and flows similar to the Harvard pump and other pulsatile blood pumps.

  9. Cerebral blood flow in the neonate.

    Science.gov (United States)

    Vutskits, Laszlo

    2014-01-01

    Ensuring adequate oxygenation of the developing brain is the cornerstone of neonatal critical care. Despite decades of clinical research dedicated to this issue of paramount importance, our knowledge and understanding regarding the physiology and pathophysiology of neonatal cerebral blood flow are still rudimentary. This review primarily focuses on currently available human clinical and experimental data on cerebral blood flow and autoregulation in the preterm and term infant. Limitations of systemic blood pressure values as surrogates for monitoring adequate cerebral oxygen delivery are discussed. Particular emphasis is placed on the high interindividual variability in cerebral blood flow values, vasoreactivity, and autoregulatory thresholds making the applications of normative values highly questionable. Technical and ethical difficulties to conduct such trials leave us with a near complete lack of knowledge on how pharmacological and surgical interventions impact on cerebral autoregulation. The ensemble of these works argues for the necessity of highly individualized care by taking advantage of continuous bedside monitoring of cerebral circulation. They also point to the urgent need for further studies addressing the exciting but difficult issue of cerebral blood flow autoregulation in the neonate.

  10. Blood flow characteristics in the aortic arch

    Science.gov (United States)

    Prahl Wittberg, Lisa; van Wyk, Stevin; Mihaiescu, Mihai; Fuchs, Laszlo; Gutmark, Ephraim; Backeljauw, Philippe; Gutmark-Little, Iris

    2012-11-01

    The purpose with this study is to investigate the flow characteristics of blood in the aortic arch. Cardiovascular diseases are associated with specific locations in the arterial tree. Considering atherogenesis, it is claimed that the Wall Shear Stress (WSS) along with its temporal and spatial gradients play an important role in the development of the disease. The WSS is determined by the local flow characteristics, that in turn depends on the geometry as well as the rheological properties of blood. In this numerical work, the time dependent fluid flow during the entire cardiac cycle is fully resolved. The Quemada model is applied to account for the non-Newtonian properties of blood, an empirical model valid for different Red Blood Cell loading. Data obtained through Cardiac Magnetic Resonance Imaging have been used in order to reconstruct geometries of the the aortic arch. Here, three different geometries are studied out of which two display malformations that can be found in patients having the genetic disorder Turner's syndrome. The simulations show a highly complex flow with regions of secondary flow that is enhanced for the diseased aortas. The financial support from the Swedish Research Council (VR) and the Sweden-America Foundation is gratefully acknowledged.

  11. In situ assessment of the role of the beta 1-, beta 2- and beta 3-adrenoceptors in the control of lipolysis and nutritive blood flow in human subcutaneous adipose tissue.

    Science.gov (United States)

    Barbe, P.; Millet, L.; Galitzky, J.; Lafontan, M.; Berlan, M.

    1996-01-01

    1. The involvement of beta 1-, beta 2- and beta 3-adrenoceptors in the control of lipolysis and nutritive blood flow was investigated in abdominal subcutaneous adipose tissue of healthy young adults by use of an in situ microdialysis technique. 2. Dialysis probes were infused either with isoprenaline (non-selective beta-adrenoceptor agonist), CGP 12,177 (selective beta 3-adrenoceptor agonist having beta 1-/beta 2-antagonist properties), dobutamine (selective beta 1-adrenoceptor agonist) or terbutaline (selective beta 2-adrenoceptor agonist). The recovery of each probe used for perfusion was calculated by an in vivo calibration method. The local blood flow was estimated through the measurement of the escape of ethanol infused simultaneously with the drugs included in the probe. 3. Isoprenaline infusion at 0.01 microM had a weak effect while higher concentrations of isoprenaline (0.1 and 1 microM) caused a rapid, sustained and concentration-dependent increase of glycerol outflow; the maximum increase was 306 +/- 34% with 1 microM. Isoprenaline also increased the nutritive blood flow in adipose tissue; a significant effect appeared at 0.1 microM isoprenaline and was greater at 1 microM. 4. CGP 12,177 (10 and 100 microM) increased the glycerol concentration in the dialysate (128 +/- 8 and 149 +/- 12%, respectively) and nutritive blood flow. Terbutaline and dobutamine (100 microM) both provoked rapid and similar increases in glycerol outflow (252 +/- 18 and 249 +/- 18%, respectively). Both, terbutaline and dobutamine increased nutritive blood flow. 5. It is concluded that beta 1- and beta 2-adrenoceptor subtypes are both mainly involved in the mobilization of lipids and in the control of nutritive blood flow. beta 3-Adrenoceptors play a weaker role in the control of lipolysis and nutritive blood flow in human subcutaneous abdominal adipose tissue. PMID:8851509

  12. Intrinsic regulation of blood flow in adipose tissue

    DEFF Research Database (Denmark)

    Henriksen, O; Nielsen, Steen Levin; Paaske, W

    1976-01-01

    Previous studies on intact human subcutaneous tissue have shown, that blood flow remains constant during minor changes in perfusion pressure. This so-called autoregulatory response has not been demonstrable in isolated preparations of adipose tissue. In the present study on isolated, denervated...... subcutaneous tissue in female rabbits only 2 of 12 expts. revealed an autoregulatory response during reduction in arterial perfusion pressure. Effluent blood flow from the tissue in the control state was 15.5 ml/100 g-min (S.D. 6.4, n = 12) corresponding to slight vasodilatation of the exposed tissue....... Following total ischemia all experiments showed a period with reactive hyperemia, and both duration of hyperemia and excess flow was related to the duration of the ischemia. This response therefore seems more resistant to the experimental procedure, while autoregulation of blood flow to lowered pressure...

  13. Transcutaneous measurement of volume blood flow

    Science.gov (United States)

    Daigle, R. E.; Mcleod, F. D.; Miller, C. W.; Histand, M. B.; Wells, M. K.

    1974-01-01

    Blood flow velocity measurements, using Doppler velocimeter, are described. The ability to measure blood velocity using ultrasound is derived from the Doppler effect; the change in frequency which occurs when sound is reflected or transmitted from a moving target. When ultrasound of the appropriate frequency is transmitted through a moving blood stream, the blood cells act as point scatterers of ultrasonic energy. If this scattered ultrasonic energy is detected, it is found to be shifted in frequency according to the velocity of the blood cells, nu, the frequency of the incident sound, f sub o, the speed of sound in the medium, c, and the angle between the sound beam and the velocity vector, o. The relation describing this effect is known as the Doppler equation. Delta f = 2 f sub o x nu x cos alpha/c. The theoretical and experimental methods are evaluated.

  14. Control of Unstable Flows

    Institute of Scientific and Technical Information of China (English)

    刘曾荣; 茅坚民

    2003-01-01

    Without introducing a discrete model, unstable continuous flows in a neighbourhood of an unstable stationary point can be stabilized. The linear part of the vector field of disturbing the flow can be managed to become the state variable multiplied by a negative constant. The nonlinear part of the vector field keeps to be unchanged,therefore flows far away from the stationary point are almost unaffected by the disturbance. The control method is easy to be used, even for practical problems for which a priori analytical knowledge of system dynamics is unavailable.

  15. Blood flow dynamics in the snake spectacle.

    Science.gov (United States)

    van Doorn, Kevin; Sivak, Jacob G

    2013-11-15

    The eyes of snakes are shielded beneath a layer of transparent integument referred to as the 'reptilian spectacle'. Well adapted to vision by virtue of its optical transparency, it nevertheless retains one characteristic of the integument that would otherwise prove detrimental to vision: its vascularity. Given the potential consequence of spectacle blood vessels on visual clarity, one might expect adaptations to have evolved that mitigate their negative impact. Earlier research demonstrated an adaptation to their spatial layout in only one species to reduce the vessels' density in the region serving the foveal and binocular visual fields. Here, we present a study of spectacle blood flow dynamics and provide evidence of a mechanism to mitigate the spectacle blood vessels' deleterious effect on vision by regulation of blood flow through them. It was found that when snakes are at rest and undisturbed, spectacle vessels undergo cycles of dilation and constriction, such that the majority of the time the vessels are fully constricted, effectively removing them from the visual field. When snakes are presented with a visual threat, spectacle vessels constrict and remain constricted for longer periods than occur during the resting cycles, thus guaranteeing the best possible visual capabilities in times of need. Finally, during the snakes' renewal phase when they are generating a new stratum corneum, the resting cycle is abolished, spectacle vessels remain dilated and blood flow remains strong and continuous. The significance of these findings in terms of the visual capabilities and physiology of snakes is discussed.

  16. Regional cerebral blood flow in aphasia

    DEFF Research Database (Denmark)

    Soh, K; Larsen, B; Skinhøj, E

    1978-01-01

    Regional cerebral blood flow (rCBF) was studied in 13 aphasic patients with left hemisphere lesions, using the intracarotid xenon 133 injection method and a 254-detector gamma camera system. The rCBF was measured during rest and during various function tests, including a simple speech test...

  17. Effects of aortic irregularities on blood flow.

    Science.gov (United States)

    Prahl Wittberg, Lisa; van Wyk, Stevin; Fuchs, Laszlo; Gutmark, Ephraim; Backeljauw, Philippe; Gutmark-Little, Iris

    2016-04-01

    Anatomic aortic anomalies are seen in many medical conditions and are known to cause disturbances in blood flow. Turner syndrome (TS) is a genetic disorder occurring only in females where cardiovascular anomalies, particularly of the aorta, are frequently encountered. In this study, numerical simulations are applied to investigate the flow characteristics in four TS patient- related aortic arches (a normal geometry, dilatation, coarctation and elongation of the transverse aorta). The Quemada viscosity model was applied to account for the non-Newtonian behavior of blood. The blood is treated as a mixture consisting of water and red blood cells (RBC) where the RBCs are modeled as a convected scalar. The results show clear geometry effects where the flow structures and RBC distribution are significantly different between the aortas. Transitional flow is observed as a jet is formed due to a constriction in the descending aorta for the coarctation case. RBC dilution is found to vary between the aortas, influencing the WSS. Moreover, the local variations in RBC volume fraction may induce large viscosity variations, stressing the importance of accounting for the non-Newtonian effects.

  18. Ergot alkaloids decrease rumen epithelial blood flow

    Science.gov (United States)

    Two experiments were conducted to determine if ergot alkaloids affect blood flow to the absorptive surface of the rumen of steers. Steers (n=8 total) were pair-fed alfalfa cubes at 1.5× NEM and received ground endophyte-infected tall fescue seed (E+) or endophyte-free tall fescue seed (E-) via rumen...

  19. Cerebral blood flow in acute mountain sickness

    DEFF Research Database (Denmark)

    Jensen, J B; Wright, Anne; Lassen, N A

    1990-01-01

    Changes in cerebral blood flow (CBF) were measured using the radioactive xenon technique and were related to the development of acute mountain sickness (AMS). In 12 subjects, ascending from 150 to 3,475 m, CBF was 24% increased at 24 h [45.1 to 55.9 initial slope index (ISI) units] and 4% increased...

  20. Frequency encoding in renal blood flow regulation

    DEFF Research Database (Denmark)

    Marsh, D.J.; Sosnovtseva, Olga; Pavlov, A.N.

    2005-01-01

    With a model of renal blood flow regulation, we examined consequences of tubuloglomerular feedback (TGF) coupling to the myogenic mechanism via voltage-gated Ca channels. The model reproduces the characteristic oscillations of the two mechanisms and predicts frequency and amplitude modulation...

  1. Controlled study on the effect of pentoxifylline and an ergot alkaloid derivative on regional cerebral blood flow in patients with chronic cerebrovascular disease

    Energy Technology Data Exchange (ETDEWEB)

    Hartmann, A.; Tsuda, Y.

    1988-05-01

    Regional cerebral blood flow (rCBF) in 90 patients with CBF decreased due to vascular diseases was studied by using the xenon 133 inhalation technique and a 32-detector setup. Whereas 30 patients received their standard basic therapy only and were regarded as controls, 30 others received 3 x 2 mg/day of an ergot alkaloid (co-dergocrine mesylate), and 30 others received 3 x 400 mg pentoxifylline (slow-release formulation)/day orally. Therapy was performed for eight weeks and CBF measured before start of treatment, after a four-week treatment period, and at the end of the study. CBF did not change significantly in the control group; both the pentoxifylline and the ergot alkaloid group presented with a significant increase in the CBF. This positive effect was significantly more pronounced in the pentoxifylline group and affected more ischemic than other brain tissues. In addition, symptoms like sleep disturbances, vertigo, and tinnitus improved significantly during the pentoxifylline observation period.

  2. Effects of the. cap alpha. -adrenoceptor antagonists phentolamine, phenoxybenzamine, and Idazoxan on sympathetic blood flow control in the periodontal ligament of the cat

    Energy Technology Data Exchange (ETDEWEB)

    Edwall, B.; Gazelius, B.

    1988-01-01

    Blood flow changes in the periodontal ligament (PDL) were measured indirectly by monitoring the local clearance of /sup 125/I/sup -/ during electric sympathetic nerve stimulation or close intra-arterial infusions of either noradrenaline (NA) or adrenaline (ADR) before and after administration of phentolamine (PA), phenoxybenzamine (PBZ) or Idazoxan (RX). At the doses used in the present study, PA was the only antagonist that significantly reduced the blood flow decrease seen on activation of sympathetic fibers, although PBZ also reduced this response. Idazoxan, however, did not induce the consistent effect on blood flow decreases seen on sympathetic activation. All three ..cap alpha..-adrenoceptor antagonists almost abolished the effects of exogenously administered NA and ADR. The results suggest the presence of functional post-junctional adrenoceptors of both the ..cap alpha.. 1 and ..cap alpha.. 2 subtypes in the sympathetic regulation of the blood flow in the PDL of the cat. A component of the response elicited by electrical sympathetic stimulation appeared to be resistant to ..cap alpha..-adrenoceptor blockade. Administration of guanethidine (which inhibits further release of NA and neuropeptide Y) after PA abolished this residual sympathetic response. 32 refs.

  3. Nonuniform blood flow in the canine left ventricle.

    Science.gov (United States)

    Flynn, A E; Coggins, D L; Austin, R E; Muehrcke, D D; Aldea, G S; Goto, M; Doucette, J W; Hoffman, J I

    1990-11-01

    In order to investigate the relationship between coronary perfusion pressure and blood flow distribution in the left ventricle (LV), we measured myocardial blood flow in small regions using radioactive microspheres in six anesthetized, open-chest dogs. Mean coronary perfusion pressure (CPP) was controlled with a femoral artery to left main coronary artery shunt which included a pressurized, servo-controlled blood reservoir. In each dog, we measured flow in 192 regions of the LV free wall (mean weight per region = 206 +/- 38 mg) at different perfusion pressures. At CPP = 80 mm Hg, blood flow to individual regions varied fourfold (0.30 to 1.18 ml/min/g; relative dispersion (RD) = 21.8 +/- 2.3%). At CPP = 50 mm Hg, flow varied over sevenfold (0.08 to 0.60 ml/min/g; RD = 42.8 +/- 10%; P less than 0.01 vs 80 mm Hg). This relationship between flow variability and CPP was present within individual LV layers as well between layers and is much higher than the error associated with the microsphere technique. We conclude that blood flow to small regions of the LV is markedly nonuniform. This heterogeneity becomes more profound at lower CPP. These findings suggest that (1) global measurements of coronary flow must be interpreted with caution, and (2) even in hearts with normal coronary arteries some regions of the LV are more susceptible to ischemia than others. In addition, these findings may help explain the patchy nature of myocardial damage that occurs following periods of low coronary pressure or inadequate myocardial protection during cardiopulmonary bypass.

  4. Renal blood flow in experimental septic acute renal failure

    NARCIS (Netherlands)

    Langenberg, C.; Wan, L.; Egi, M.; May, C. N.; Bellomo, R.

    2006-01-01

    Reduced renal blood flow (RBF) is considered central to the pathogenesis of septic acute renal failure (ARF). However, no controlled experimental studies have continuously assessed RBF during the development of severe septic ARF. We conducted a sequential animal study in seven female Merino sheep. F

  5. Increased cerebral blood flow in preeclampsia with magnetic resonance imaging

    NARCIS (Netherlands)

    Zeeman, GG; Hatab, MR; Twickler, DM

    2004-01-01

    Objective: The purpose of this study was to compare third trimester and nonpregnant cerebral blood flow of women with preeclampsia to normotensive control subjects with the use of magnetic resonance imaging techniques. Study design: Nine normotensive pregnant women and 12 untreated women with preecl

  6. Influence of blood flow on the coagulation cascade

    DEFF Research Database (Denmark)

    The influence of diffusion and convetive flows on the blood coagulation cascade is investigated for a controlled perfusion experiment. We present a cartoon model and reaction schemes for parts of the coagulation cascade with sunsequent set up of a mathematical model in two space dimensions plus one...

  7. Ocular Blood Flow and Normal Tension Glaucoma

    Directory of Open Access Journals (Sweden)

    Ning Fan

    2015-01-01

    Full Text Available Normal tension glaucoma (NTG is known as a multifactorial optic neuropathy characterized by progressive retinal ganglion cell death and glaucomatous visual field loss, even though the intraocular pressure (IOP does not exceed the normal range. The pathophysiology of NTG remains largely undetermined. It is hypothesized that the abnormal ocular blood flow is involved in the pathogenesis of this disease. A number of evidences suggested that the vascular factors played a significant role in the development of NTG. In recent years, the new imaging techniques, fluorescein angiography, color Doppler imaging (CDI, magnetic resonance imaging (MRI, and laser speckle flowgraphy (LSFG, have been used to evaluate the ocular blood flow and blood vessels, and the impaired vascular autoregulation was found in patients with NTG. Previous studies showed that NTG was associated with a variety of systemic diseases, including migraine, Alzheimer’s disease, primary vascular dysregulation, and Flammer syndrome. The vascular factors were involved in these diseases. The mechanisms underlying the abnormal ocular blood flow in NTG are still not clear, but the risk factors for glaucomatous optic neuropathy likely included oxidative stress, vasospasm, and endothelial dysfunction.

  8. Power flow controller

    NARCIS (Netherlands)

    Ferreira, J.A.; Yuan, Z.; De Haan, S.W.H.

    2008-01-01

    The invention relates to a power flow controller, comprising at least one first converter coupled with a power transmission line, and at least one second converter coupled with a power source, wherein said power source operates at a predeter-mined first frequency and connects to the power transmissi

  9. Skin temperature and subcutaneous adipose blood flow in man

    DEFF Research Database (Denmark)

    Astrup, A; Bülow, J; Madsen, J

    1980-01-01

    The abdominal subcutaneous adipose tissue blood flow (ATBF) was measured bilaterally by the 133Xe washout method. At one side of the skin (epicutaneous) temperature was varied with a temperature blanket, the other side served as control. There was a significant (P less than 0.001) positive...... correlation between skin temperature and ATBF. In the range from 25 to 37 degrees CATBF increased 9% of the control flow on average per centigrade increase in skin temperature. ATBF at the control side was uninfluenced by the contralateral variations in skin temperature. Although no better correlation could...

  10. Red blood cell clusters in Poiseuille flow

    Science.gov (United States)

    Ghigliotti, Giovanni; Selmi, Hassib; Misbah, Chaouqi; Elasmi, Lassaad

    2011-11-01

    We present 2D numerical simulations of sets of vesicles (closed bags of a lipid bilayer membrane) in a parabolic flow, a setup that mimics red blood cells (RBCs) in the microvasculature. Vesicles, submitted to sole hydrodynamical interactions, are found to form aggregates (clusters) of finite size. The existence of a maximal cluster size is pointed out and characterized as a function of the flow intensity and the swelling ratio of the vesicles. Moreover bigger clusters move at lower velocity, a fact that may prove of physiological interest. These results quantify previous observations of the inhomogeneous distribution of RBCs in vivo (Gaehtgens et al., Blood Cells 6 - 1980). An interpretation of the phenomenon is put forward based on the presence of boli (vortices) between vesicles. Both the results and the explanation can be transposed to the three-dimensional case.

  11. Deterministic Aperiodic Sickle Cell Blood Flows

    Science.gov (United States)

    Atsaves, Louis; Harris, Wesley

    2013-11-01

    In this paper sickle cell blood flow in the capillaries is modeled as a hydrodynamical system. The hydrodynamical system consists of the axisymmetric unsteady, incompressible Navier-Stokes equations and a set of constitutive equations for oxygen transport. Blood cell deformation is not considered in this paper. The hydrodynamical system is reduced to a system of non-linear partial differential equations that are then transformed into a system of three autonomous non-linear ordinary differential equations and a set of algebraic equations. We examine the hydrodynamical system to discern stable/unstable, periodic/nonperiodic, reversible/irreversible properties of the system. The properties of the solutions are driven in large part by the coefficients of the governing system of equations. These coefficients depend on the physiological properties of the sickle cell blood. The chaotic nature of the onset of crisis in sickle cell patients is identified. Research Assistant.

  12. Computational Analysis of Human Blood Flow

    Science.gov (United States)

    Panta, Yogendra; Marie, Hazel; Harvey, Mark

    2009-11-01

    Fluid flow modeling with commercially available computational fluid dynamics (CFD) software is widely used to visualize and predict physical phenomena related to various biological systems. In this presentation, a typical human aorta model was analyzed assuming the blood flow as laminar with complaint cardiac muscle wall boundaries. FLUENT, a commercially available finite volume software, coupled with Solidworks, a modeling software, was employed for the preprocessing, simulation and postprocessing of all the models.The analysis mainly consists of a fluid-dynamics analysis including a calculation of the velocity field and pressure distribution in the blood and a mechanical analysis of the deformation of the tissue and artery in terms of wall shear stress. A number of other models e.g. T branches, angle shaped were previously analyzed and compared their results for consistency for similar boundary conditions. The velocities, pressures and wall shear stress distributions achieved in all models were as expected given the similar boundary conditions. The three dimensional time dependent analysis of blood flow accounting the effect of body forces with a complaint boundary was also performed.

  13. Blood flow measurements and clot detection with nearinfrared spectroscopy

    OpenAIRE

    Rossow, MJ; Gatto, R.; D'amico, E.; Mantulin, WW; Gratton, E

    2006-01-01

    Detecting impeded blood flow and locating the clot causing it is a major challenge in neurosurgery. We propose an instrument that uses near-infrared spectroscopy to simultaneously detect clots and measure blood flow. © 2006 Optical Society of America.

  14. Blood flow characteristics in the ascending aorta after TAVI compared to surgical aortic valve replacement.

    Science.gov (United States)

    Trauzeddel, Ralf Felix; Löbe, Ulrike; Barker, Alex J; Gelsinger, Carmen; Butter, Christian; Markl, Michael; Schulz-Menger, Jeanette; von Knobelsdorff-Brenkenhoff, Florian

    2016-03-01

    Ascending aortic blood flow characteristics are altered after aortic valve surgery, but the effect of transcatheter aortic valve implantation (TAVI) is unknown. Abnormal flow may be associated with aortic and cardiac remodeling. We analyzed blood flow characteristics in the ascending aorta after TAVI in comparison to conventional stented aortic bioprostheses (AVR) and healthy subjects using time-resolved three-dimensional flow-sensitive cardiovascular magnetic resonance imaging (4D-flow MRI). Seventeen patients with TAVI (Edwards Sapien XT), 12 with AVR and 9 healthy controls underwent 4D-flow MRI of the ascending aorta. Target parameters were: severity of vortical and helical flow pattern (semiquantitative grading from 0 = none to 3 = severe) and the local distribution of systolic wall shear stress (WSSsystole). AVR revealed significantly more extensive vortical and helical flow pattern than TAVI (p = 0.042 and p = 0.002) and controls (p flow than controls (p blood flow eccentricity (64.7 and 66.7%, respectively), whereas controls showed central blood flow (88.9%). TAVI and AVR exhibited an asymmetric distribution of WSSsystole in the mid-ascending aorta with local maxima at the right anterior aortic wall and local minima at the left posterior wall. In contrast, controls showed a symmetric distribution of WSSsystole along the aortic circumference. Blood flow was significantly altered in the ascending aorta after TAVI and AVR. Changes were similar regarding WSSsystole distribution, while TAVI resulted in less helical and vortical blood flow.

  15. Modeling cerebral blood flow during posture change from sitting to standing

    DEFF Research Database (Denmark)

    Ottesen, Johnny T.; Olufsen, M.; Tran, H.T.

    2004-01-01

    extremities, the brain, and the heart. We use physiologically based control mechanisms to describe the regulation of cerebral blood flow velocity and arterial pressure in response to orthostatic hypotension resulting from postural change. To justify the fidelity of our mathematical model and control......Abstract Hypertension, decreased cerebral blood flow, and diminished cerebral blood flow velocity regulation, are among the first signs indicating the presence of cerebral vascular disease. In this paper, we will present a mathematical model that can predict blood flow and pressure during posture...

  16. Controllability of flow turbulence.

    Science.gov (United States)

    Guan, Shuguang; Wei, G W; Lai, C-H

    2004-06-01

    In this paper, we study the controllability of real-world flow turbulence governed by the two-dimensional Navier-Stokes equations, using strategies developed in chaos control. A case of control/synchronization of turbulent dynamics is observed when only one component of the velocity field vector is unidirectionally coupled to a target state, while the other component is uncoupled. Unlike previous results, it is shown that the dynamics of the whole velocity field cannot be completely controlled/synchronized to the target, even in the limit of long time and strong coupling strength. It is further revealed that the controlled component of the velocity field can be fully controlled/synchronized to the target, but the other component, which is not directly coupled to the target, can only be partially controlled/synchronized to the target. By extending an auxiliary method to distributed dynamic systems, the partial synchronization of two turbulent orbits in the present study can be categorized in the domain of generalized synchronization of spatiotemporal dynamics.

  17. Blood flow in healed and inflamed periodontal tissues of dogs

    Energy Technology Data Exchange (ETDEWEB)

    Hock, J.M.; Kim, S.

    1987-01-01

    The objectives of this study were to determine if increased blood flow associated with gingivitis would decrease following resolution of gingival inflammation in dogs with periodontitis; if increased blood flow in inflamed gingiva was associated with changes in the blood flow of alveolar bone, and if blood flow in gingiva and alveolar bone increased if periodontitis was reactivated by ligating teeth. Regional blood flow was measured in dogs with pre-existing periodontitis, using radioisotope-labelled, plastic microspheres. In the first experiment on 4 adult Beagle dogs, teeth in the left jaws were treated to resolve the periodontitis, while teeth in the right jaws were not treated. Gingival and bone blood flow were measured after 12 wk. Blood flow was significantly (p<0.05) lower in non-inflamed healed gingiva (32.1 +- 2.7 ml/min/100 g) than in inflamed gingiva (46.1 +- 5.3 ml/min/100 g). No differences in the blood flow of the alveolar bone underlying inflamed or non-inflamed gingiva were present. In the second experiment, the right mandibular teeth of 5 dogs were treated to resolve periodontitis while teeth in the other quadrants were ligated for 4, 10 or 12 wk. The duration of ligation did not alter blood flow. Gingival blood flow around ligated maxillary and mandibular teeth was comparable and approximately 54% higher than around non-ligated teeth (p<0.03). The difference in blood flow between gingiva with G.I.>1 and gingiva with G.I.<2 was significant (p<0.04). Blood flow in bone was not altered by changes in the inflammatory status of the overlying gingiva. The findings suggest that changes in blood flow associated with inflammation are reversible and that blood flow alveolar bone is regulated independently of gingival blood flow.

  18. Skin blood flow changes during apneic spells in preterm infants

    NARCIS (Netherlands)

    Suichies, H.E.; Aarnoudse, J.G.; Okken, A.; Jentink, H.W.; Mul, de F.F.M.; Greve, J.

    1989-01-01

    Changes in skin blood flow during apneic spells were determined in 18 preterm infants using a diode laser Doppler flow meter without light conducting fibres. Heart rate, nasal air flow, impedance pneumography, skin and incubator temperature and laser Doppler skin blood flow were recorded simultaneou

  19. Nonlinear interactions in renal blood flow regulation

    DEFF Research Database (Denmark)

    Marsh, Donald J.; Sosnovtseva, Olga; Chon, Ki H.

    2005-01-01

    , identical except for the strength of TGF input, with a third, fixed resistance segment representing prearteriolar vessels. The two arteriolar segments are electrically coupled. The arteriolar, glomerular, and tubular models are linked; TGF modulates arteriolar circumference, which determines vascular...... resistance and glomerular capillary pressure. The model couples TGF input to voltage-gated Ca channels. It predicts autoregulation of GFR and renal blood flow, matches experimental measures of tubular pressure and macula densa NaCl concentration, and predicts TGF-induced oscillations and a faster smaller...

  20. Absolute quantification of myocardial blood flow.

    Science.gov (United States)

    Yoshinaga, Keiichiro; Manabe, Osamu; Tamaki, Nagara

    2016-07-21

    With the increasing availability of positron emission tomography (PET) myocardial perfusion imaging, the absolute quantification of myocardial blood flow (MBF) has become popular in clinical settings. Quantitative MBF provides an important additional diagnostic or prognostic information over conventional visual assessment. The success of MBF quantification using PET/computed tomography (CT) has increased the demand for this quantitative diagnostic approach to be more accessible. In this regard, MBF quantification approaches have been developed using several other diagnostic imaging modalities including single-photon emission computed tomography, CT, and cardiac magnetic resonance. This review will address the clinical aspects of PET MBF quantification and the new approaches to MBF quantification.

  1. Decorrelation-based blood flow velocity estimation: effect of spread of flow velocity, linear flow velocity gradients, and parabolic flow.

    NARCIS (Netherlands)

    Lupotti, F.A.; Steen, A.F.W. van der; Mastik, F.; Korte, C.L. de

    2002-01-01

    In recent years, a new method to measure transverse blood flow, based on the decorrelation of the radio frequency (RF) signals has been developed. In this paper, we investigated the influence of nonuniform flow on the velocity estimation. The decorrelation characteristics of transverse blood flow us

  2. Regional cerebral blood flow in schizophrenics

    Energy Technology Data Exchange (ETDEWEB)

    Uchino, J.; Ohta, Y.; Nakane, Y.; Mori, H.; Hirota, N.; Yonekura, M.

    1987-01-01

    The present study on schizophrenics dealt with the relationship of regional cerebral blood flow (rCBF) to age, disease duration, and treatment length with chlorpromazine hydrochloride (CPZ). Regional cerebral blood flow in 28 cerebral regions of interest was measured by iv injection of /sup 133/X in 54 schizophrenic patients and 39 healthy volunteers. Neither age nor dosage of CPZ significantly influenced rCBF. All patients, including 11 treated for a short period of time (6 months or less), were characterized by having a decreased rCBF over the whole cerebrum. Thirty-four patients treated for a long period of time (2 years or more) had a varied rCBF distribution in the left hemisphere, with the most predominant feature being the decrease in rCBF in the frontal lobe (i.e., hypofrontality); however, there was no linear correlation between rCBF and disease duration. A decreased rCBE in the right occipital region was seen in patients with paranoid schizophrenia, suggesting that manifestations of symptoms may depend on disturbed regions. These results suggest that cerebral dysfunction in schizophrenic patients may not be restricted to the frontal lobe, but cover the whole cerebrum, and that nonuniform dysfunction in various regions of the cerebrum, including the frontal lobe, may be involved in manifestations of symptoms.

  3. Cerebral blood flow tomography with xenon-133

    Energy Technology Data Exchange (ETDEWEB)

    Lassen, N.A.

    1985-10-01

    Cerebral blood flow (CBF) can be measured tomographically by inhalation of Xenon-/sup 133/. The calculation is based on taking a sequence of tomograms during the wash-in and wash-out phase of the tracer. Due to the dynamic nature of the process, a highly sensitive and fast moving single photon emission computed tomograph (SPECT) is required. Two brain-dedicated SPECT systems designed for this purpose are mentioned, and the method is described with special reference to the limitations inherent in the soft energy of the 133Xe primary photons. CBF tomography can be used for a multitude of clinical and investigative purposes. This article discusses in particular its use for the selection of patients with carotid occlusion for extracranial/intracranial bypass surgery, for detection of severe arterial spasm after aneurysm bleeding, and for detection of low flow areas during severe migraine attacks. The use of other tracers for CBF tomography using SPECT is summarized with emphasis on the /sup 99m/Tc chelates that freely pass the intact blood-brain barrier. The highly sensitive brain-dedicated SPECT systems described are a prerequisite for achieving high resolution tomograms with such tracers.

  4. Tissue blood flow mapping using laser technology

    Science.gov (United States)

    Wardell, Karin; Linden, Maria; Nilsson, Gert E.

    1995-03-01

    By the introduction of the laser Doppler perfusion imager (LDPI) the microvascular blood flow in a tissue area can be mapped by sequentially moving a laser beam over the tissue. The measurement is performed without touching the tissue and the captured perfusion values in the peripheral circulation are presented as a color-coded image. In the ordinary LDPI-set-up, 64 X 64 measurement sites cover an area in the range of about 10 - 150 cm2 depending on system settings. With a high resolution modification, recordings can be done on tissue areas as small as 1 cm2. This high resolution option has been assessed in animal models for the mapping of small vessels. To be able to record not only spatial but also temporal perfusion components of tissue blood flow, different local area scans (LAS) have been developed. These include single point recording as well as integration of either 2 X 2, 3 X 3, or 4 X 4 measurement sites. The laser beam is repeatedly moved in a quadratic pattern over the small tissue area of interest and the output value constitutes the average perfusion of all captured values within the actual region. For the evaluation, recordings were performed on healthy volunteers before and after application of a vasodilatating cream on the dorsal side of the hand.

  5. Effects of liraglutide on neurodegeneration, blood flow and cognition in Alzheimer´s disease - protocol for a controlled, randomized double-blinded trial

    DEFF Research Database (Denmark)

    Egefjord, Lærke; Jensen, Michael Gejl; Møller, Arne;

    2012-01-01

    Introduction: Type 2 diabetes (DM-2) increases the risk of developing Alzheimer’s disease (AD), and patients with AD are more likely to develop DM-2. DM-2 and AD share some pathophysiological features. In AD, amyloid-β (Aβ) is accumulated as extracellular plaques in the gray matter of the brain......, a perfusion-weighted magnetic resonance imaging with contrast will be performed to evaluate blood flow. Conclusion: No registered drug affects the deposition of Aβ in the brain of AD patients. Our goal is to find a new therapeutic agent that alters the pathophysiology in AD patients by decreasing...

  6. Resistance exercise with different volumes: blood pressure response and forearm blood flow in the hypertensive elderly

    Science.gov (United States)

    Brito, Aline de Freitas; de Oliveira, Caio Victor Coutinho; Brasileiro-Santos, Maria do Socorro; Santos, Amilton da Cruz

    2014-01-01

    Background The purpose of this study was to evaluate the effect of two sessions of resistance exercise with different volumes on post-exercise hypotension, forearm blood flow, and forearm vascular resistance in hypertensive elderly subjects. Methods The study was conducted with ten hypertensive elderly (65±3 years, 28.7±3 kg/m2) subjected to three experimental sessions, ie, a control session, exercise with a set (S1), and exercise with three sets (S3). For each session, the subjects were evaluated before and after intervention. In the pre-intervention period, blood pressure, forearm blood flow, and forearm vascular resistance were measured after 10 minutes of rest in the supine position. Thereafter, the subjects were taken to the gym to perform their exercise sessions or remained at rest during the same time period. Both S1 and S3 comprised a set of ten repetitions of ten exercises, with an interval of 90 seconds between exercises. Subsequently, the measurements were again performed at 10, 30, 50, 70, and 90 minutes of recovery (post-intervention) in the supine position. Results Post-exercise hypotension was greater in S3 than in S1 (systolic blood pressure, −26.5±4.2 mmHg versus −17.9±4.7 mmHg; diastolic blood pressure, −13.8±4.9 mmHg versus −7.7±5 mmHg, P<0.05). Similarly, forearm blood flow and forearm vascular resistance changed significantly in both sessions with an increase and decrease, respectively, that was more evident in S3 than in S1 (P<0.05). Conclusion Resistance exercises with higher volume were more effective in causing post-exercise hypotension, being accompanied by an increase in forearm blood flow and a reduction of forearm vascular resistance. PMID:25540580

  7. Why control blood glucose levels?

    Science.gov (United States)

    Rossini, A A

    1976-03-01

    The controversy as to the relationship between the degree of control of diabetes and the progression of the complications of the disease has not been solved. However, in this review, various studies suggesting a relationship between the metabolic abnormality and the diabetic complications are examined. The disadvantages of the uncontrolled diabetes mellitus can be divided into two major categories-short-term and long-term. The short-term disadvantages of controlled diabetes mellitus include the following: (1) ketoacidosis and hyperosmolar coma; (2) intracellular dehydration; (3) electrolyte imbalance; (4) decreased phagocytosis; (5) immunologic and lymphocyte activity; (6) impairment of wound healing; and (7) abnormality of lipids. The long-term disadvantages of uncontrolled diabetes melitus include the following: (1) nephropathy; (2) neuropathy; (3) retinopathy; (4) cataract formation; (5) effect on perinatal mortality; (6) complications of vascular disease; and (7) the evaluation of various clinical studies suggesting the relationship of elevated blood glucose levels and complications of diabetes mellitus. It is suggested that until the question of control can absolutely be resolved, the recommendation is that the blood glucose levels should be controlled as close to the normal as possible.

  8. Quantitative retinal blood flow mapping from fluorescein videoangiography using tracer kinetic modeling.

    Science.gov (United States)

    Tichauer, Kenneth M; Guthrie, Micah; Hones, Logan; Sinha, Lagnojita; St Lawrence, Keith; Kang-Mieler, Jennifer J

    2015-05-15

    Abnormal retinal blood flow (RBF) has been associated with numerous retinal pathologies, yet existing methods for measuring RBF predominantly provide only relative measures of blood flow and are unable to quantify volumetric blood flow, which could allow direct patient to patient comparison. This work presents a methodology based on linear systems theory and an image-based arterial input function to quantitatively map volumetric blood flow from standard fluorescein videoangiography data, and is therefore directly translatable to the clinic. Application of the approach to fluorescein retinal videoangiography in rats (4 control, 4 diabetic) demonstrated significantly higher RBF in 4-5 week diabetic rats as expected from the literature.

  9. Subcutaneous blood flow in man during sleep with continous epdural anaesthesia

    DEFF Research Database (Denmark)

    Sindrup, JH; Petersen, Lars Jelstrup; Kastrup, Jens;

    1996-01-01

    BACKGROUND: Subcutaneous blood flow increases during sleep and we evaluated if this increase is affected by epidural anaesthesia. METHODS: Lower leg subcutaneous blood flow was determined by 133Xenon clearance in ten subjects during continous epidural anaesthesia at L2-L3 including eight hours...... of sleep, while the opper abdominal subcutaneous blood flow served as control. RESULTS: Epidural anaesthesia to the level of the umbilicus was followed by an increase in the lower leg subcutaneous blood flow fra 3.4 (1.8-6.3) to 7.8 (3.6-16.9) ml min-1 (median and range; P...-1 100 g-1 after 34 (29-70) min (Pepidural anaesthesia induced only a temporary increase in lower leg subcutaneous blood flow, it hindered the rise in subcutaneous blood flow normally manifest...

  10. A double-blind, placebo-controlled study evaluating the effects of caffeine and L-theanine both alone and in combination on cerebral blood flow, cognition and mood

    OpenAIRE

    2015-01-01

    Rationale -Evidence suggests interactive effects of the tea components caffeine and L-theanine on behaviour, yet no data exists exploring the impact of the two on cerebral blood flow (CBF).\\ud \\ud Objectives - The current placebo-controlled, double-blind, counterbalanced, crossover study examined the effects of caffeine and L-theanine on CBF and extended previous cognitive and mood findings by using lower doses than previous studies of a similar methodology, which more closely reflect the rat...

  11. Low cerebral blood flow in hypotensive perinatal distress

    DEFF Research Database (Denmark)

    Lou, H C; Lassen, N A; Friis-Hansen, B

    1977-01-01

    was used for the cerebral blood flow measurements. The study confirmed that perinatal distress may be associated with low arterial blood pressure, and it was shown that cerebral blood flow is very low, 20 ml/100 g/min or less, in hypotensive perinatal distress. It is concluded that cerebral ischaemia plays...

  12. Methods for blood flow measurements using ultrasound contrast agents

    Science.gov (United States)

    Fowlkes, J. Brian

    2003-10-01

    Blood flow measurements using ultrasound contrast agents are being investigated for myocardial perfusion and more recently in other organ systems. The methods are based largely on the relative increase in echogenicity due to the concentration of bubbles present in the ultrasound beam. In the simplest form, regional differences in blood volume can be inferred but the possibility exists to extract perfusion from the transit of contrast agent through tissue. Perfusion measurements rely on determining the flux of blood through a tissue volume and as such require knowledge of the fractional blood volume (FBV), i.e., ml blood/g tissue and the rate of exchange, commonly measured as the mean transit time (MTT). This presentation will discuss methods of determining each of these values and their combination to estimate tissue perfusion. Underlying principles of indicator-dilution theory will be provided in the context of ultrasound contrast agents. Current methods for determining MTT will include imaging of the intravenous bolus, in-plane contrast disruption with interval and real-time contrast recovery imaging, and control of contrast agent flow using arterial disruption (contrast interruption). The advantages and limitations of the methods will be examined along with current applications. [Work supported in part by NIH.

  13. Intensive Insulin Therapy: Tight Blood Sugar Control

    Science.gov (United States)

    ... insulin therapy can help you achieve desired blood sugar control and what intensive insulin therapy requires of ... aggressive treatment approach designed to control your blood sugar levels. Intensive insulin therapy requires close monitoring of ...

  14. Control Blood Pressure, Protect Your Kidneys

    Science.gov (United States)

    ... Bar Home Current Issue Past Issues Health Lines Control Blood Pressure, Protect Your Kidneys Past Issues / Fall ... Not Alone / Keep Weight Off / Facts About Fat / Control Blood Pressure, Protect Your Kidneys Fall 2008 Issue: ...

  15. Effect of spinal sympathetic blockade upon postural changes of blood flow in human peripheral tissues

    DEFF Research Database (Denmark)

    Skagen, K; Haxholdt, O; Henriksen, O

    1982-01-01

    local nervous blockade was induced by Lidocaine in 133Xe labelled subcutaneous tissue on one side. During epidural blockade and tilt blood flow increased by 12% whereas blood flow decreased by 30% on the control side. Thus epidural blockade had no influence on the vasoconstrictor response...

  16. Subcutaneous blood flow in early male pattern baldness

    Energy Technology Data Exchange (ETDEWEB)

    Klemp, P.; Peters, K.; Hansted, B.

    1989-05-01

    The subcutaneous blood flow (SBF) was measured by the /sup 133/Xe washout method in the scalp of 14 patients with early male pattern baldness. Control experiments were performed in 14 normal haired men matched for age. The SBF in the scalp of the normal individuals was about 10 times higher than previously reported SBF values in other anatomical regions. In patients with early male pattern baldness, SBF was 2.6 times lower than the values found in the normal individuals (13.7 +/- 9.6 vs 35.7 +/- 10.5 ml/100 g/min-1). This difference was statistically significant (p much less than 0.001). A reduced nutritive blood flow to the hair follicles might be a significant event in the pathogenesis of early male pattern baldness.

  17. Intraoperative cerebral blood flow imaging of rodents

    Science.gov (United States)

    Li, Hangdao; Li, Yao; Yuan, Lu; Wu, Caihong; Lu, Hongyang; Tong, Shanbao

    2014-09-01

    Intraoperative monitoring of cerebral blood flow (CBF) is of interest to neuroscience researchers, which offers the assessment of hemodynamic responses throughout the process of neurosurgery and provides an early biomarker for surgical guidance. However, intraoperative CBF imaging has been challenging due to animal's motion and position change during the surgery. In this paper, we presented a design of an operation bench integrated with laser speckle contrast imager which enables monitoring of the CBF intraoperatively. With a specially designed stereotaxic frame and imager, we were able to monitor the CBF changes in both hemispheres during the rodent surgery. The rotatable design of the operation plate and implementation of online image registration allow the technician to move the animal without disturbing the CBF imaging during surgery. The performance of the system was tested by middle cerebral artery occlusion model of rats.

  18. Mapping blood flow directionality in the human brain.

    Science.gov (United States)

    Park, Sung-Hong; Do, Won-Joon; Choi, Seung Hong; Zhao, Tiejun; Bae, Kyongtae Ty

    2016-07-01

    Diffusion properties of tissue are often expressed on the basis of directional variance, i.e., diffusion tensor imaging. In comparison, common perfusion-weighted imaging such as arterial spin labeling yields perfusion in a scalar quantity. The purpose of this study was to test the feasibility of mapping cerebral blood flow directionality using alternate ascending/descending directional navigation (ALADDIN), a recently-developed arterial spin labeling technique with sensitivity to blood flow directions. ALADDIN was applied along 3 orthogonal directions to assess directional blood flow in a vector form and also along 6 equally-spaced directions to extract blood flow tensor matrix (P) based on a blood flow ellipsoid model. Tensor elements (eigenvalues, eigenvectors, etc) were calculated to investigate characteristics of the blood flow tensor, in comparison with time-of-flight MR angiogram. While the directions of the main eigenvectors were heterogeneous throughout the brain, regional clusters of blood flow directionality were reproducible across subjects. The technique could show heterogeneous blood flow directionality within and around brain tumor, which was different from that of the contralateral normal side. The proposed method is deemed to provide information of blood flow directionality, which has not been demonstrated before. The results warrant further studies to assess changes in the directionality map as a function of scan parameters, to understand the signal sources, to investigate the possibility of mapping local blood perfusion directionality, and to evaluate its usefulness for clinical diagnosis.

  19. The effect of hyperosmotic solutions on the hepatic blood flow

    DEFF Research Database (Denmark)

    Winkler, K; Henriksen, Jens Henrik Sahl; Tygstrup, N

    1993-01-01

    The present study was undertaken in order to measure the effect of hyperosmotic solutions on portal and hepatic blood flow. In five anaesthetized pigs without arterial blood supply to the liver, portal blood flow rate was measured (electromagnetic flowmeter) during 5 min lasting intravenous infus...... for these osmotic effects are not known, but they have to be taken into consideration in studies of the portal and hepatic blood flow.......The present study was undertaken in order to measure the effect of hyperosmotic solutions on portal and hepatic blood flow. In five anaesthetized pigs without arterial blood supply to the liver, portal blood flow rate was measured (electromagnetic flowmeter) during 5 min lasting intravenous...

  20. Cerebral blood flow simulations in realistic geometries

    Directory of Open Access Journals (Sweden)

    Szopos Marcela

    2012-04-01

    Full Text Available The aim of this work is to perform the computation of the blood flow in all the cerebral network, obtained from medical images as angiographies. We use free finite elements codes as FreeFEM++. We first test the code on analytical solutions in simplified geometries. Then, we study the influence of boundary conditions on the flow and we finally perform first computations on realistic meshes. L’objectif est ici de simuler l’écoulement sanguin dans tout le réseau cérébral (artériel et veineux obtenu à partir d’angiographies cérébrales 3D à l’aide de logiciels d’éléments finis libres, comme FreeFEM++. Nous menons d’abord une étude détaillée des résultats sur des solutions analytiques et l’influence des conditions limites à imposer dans des géométries simplifiées avant de travailler sur les maillages réalistes.

  1. Anisodamine augments mucosal blood flow during gut ischemia/reperfusion

    Institute of Scientific and Technical Information of China (English)

    Hu Sen; Sheng Zhiyong

    2002-01-01

    Objective: To determine if anisodamine is able to augment mucosal perfusion during gut ischemia-reperfusion (I/R). Methods: A jejunal sac was formed in Sprague Dawley rat. A Laser Doppler probe and a tonometer were inserted into the sac which was filled with saline. The superior mesenteric artery was occluded (SMAO) for 60minutes followed by 90 minutes of reperfusion. At the end of 60 minutes of SMAO, either 0.2mg/kg of anisodmine or dobutamine was injected into the jejunal sac. Laser Doppler mucosal blood flow and regional PCO2 (PrCO2) measurements were made. Results: Mucosal blood flow was significantly increased at 30,60 and 90 minutes of reperfusion (R30, R60, R90 ) when intraluminal anisodamine or dobutamine was introduced compared to intraluminal saline only (44±3.3)% or (48±4.1)% vs. (37±2.6) % at R30, (57±5.0)% or (56±4.7)% vs. (45±2.7)% at R60, (64±3.3) % or (56 ± 4.2) % vs. (48 ± 3.4) % at R90 , respectively P<0.05). Blood flow changes were also reflected by lowering of jejunal PrCO2 measurements after intraluminal anisodamine or dobutamine compared with that of the saline controls (41±3. 1)mmHg or (44±3.0)mmHg vs. (49±3.7) mmHg at R30 , (38±3.7)mmHg or (40±2. 1)mmHg vs. (47±3.8) mmHgat R60, (34±2.1) mmHg or (39± 3.0) mmHg vs. (46±3.4) mmHg at R90, respectively,P<0. 05). The most interesting finding was that there were significantly higher mucosal blood flow and lower jejunal PrCO2 in anisodamine group than those in dobutamine group at 90 minutes of reperfusion (64± 3.3) %vs. (56±4.2)% for blood flow or (34 ± 2.1)mmHg vs. (39 ± 3.0)mmHg for PrCO2, respectively, P<0.05),suggesting that anisodamine had more lasting effect on mucosal perfusion than dobutamine. Conclusions:Intraluminal anisodamine can augment mucosal blood flow during gut I/R, and it may provide the protective effect on gut from ischemia and reperfusion injury.

  2. Dynamic Effect of Rolling Massage on Blood Flow

    Institute of Scientific and Technical Information of China (English)

    CHEN Yan-Yan; YI Hou-Hui; LI Hua-Bing; FANG Hai-Ping

    2009-01-01

    The Chinese traditional medical massage has been used as a natural therapy to eliminate some diseases.Here, the effect of the rolling massage frequency to the blood flow in the blood vessels under the rolling massage manipulation is studied by the lattice Boltzmann simulation.The simulation results show that when the frequency is smaller than or comparable to the putsatile frequency of the blood flow, the effect on the blood flux by the rolling massage is small.On the contrast, if the frequency is twice or more times of the putsatile frequency of the blood flow, the blood flux is greatly enhanced and increases linearly with respect to the frequency.Similar behavior has also been observed on the shear stress on the blood vessel waits.The result is helpful for understanding that the rolling massage has the function of promoting the blood circulation and removing the blood stasis.

  3. Dynamic Effect of Rolling Massage on Blood Flow

    Science.gov (United States)

    Chen, Yan-Yan; Yi, Hou-Hui; Li, Hua-Bing; Fang, Hai-Ping

    2009-02-01

    The Chinese traditional medical massage has been used as a natural therapy to eliminate some diseases. Here, the effect of the rolling massage frequency to the blood flow in the blood vessels under the rolling massage manipulation is studied by the lattice Boltzmann simulation. The simulation results show that when the frequency is smaller than or comparable to the pulsatile frequency of the blood flow, the effect on the blood flux by the rolling massage is small. On the contrast, if the frequency is twice or more times of the pulsatile frequency of the blood flow, the blood flux is greatly enhanced and increases linearly with respect to the frequency. Similar behavior has also been observed on the shear stress on the blood vessel walls. The result is helpful for understanding that the rolling massage has the function of promoting the blood circulation and removing the blood stasis.

  4. Vascular Function and Regulation of Blood Flow in Resting and Contracting Skeletal Muscle

    DEFF Research Database (Denmark)

    Nyberg, Michael Permin

    in the regulation of exercise hyperemia. Furthermore, blood flow to contracting leg skeletal muscles is reduced both in essential hypertension and with aging. The potential difference in vasoactive system(s) responsible for the reduction in blood flow in the two conditions is in agreement with the suggestion......The precise matching of blood flow, oxygen delivery and metabolism is essential as it ensures that any increase in muscle work is precisely matched by increases in oxygen delivery. Therefore, understanding the control mechanisms of skeletal muscle blood flow regulation is of great biological...... importance. The present work provides new insight in to vasodilator interactions important for exercise hyperemia and sheds light on mechanisms important for vascular function and regulation of skeletal muscle blood flow in essential hypertension (high blood pressure) and aging and identifies mechanisms...

  5. Multiscale modeling of blood flow: from single cells to blood rheology.

    Science.gov (United States)

    Fedosov, Dmitry A; Noguchi, Hiroshi; Gompper, Gerhard

    2014-04-01

    Mesoscale simulations of blood flow, where the red blood cells are described as deformable closed shells with a membrane characterized by bending rigidity and stretching elasticity, have made much progress in recent years to predict the flow behavior of blood cells and other components in various flows. To numerically investigate blood flow and blood-related processes in complex geometries, a highly efficient simulation technique for the plasma and solutes is essential. In this review, we focus on the behavior of single and several cells in shear and microcapillary flows, the shear-thinning behavior of blood and its relation to the blood cell structure and interactions, margination of white blood cells and platelets, and modeling hematologic diseases and disorders. Comparisons of the simulation predictions with existing experimental results are made whenever possible, and generally very satisfactory agreement is obtained.

  6. Blood flow distribution with adrenergic and histaminergic antagonists

    Energy Technology Data Exchange (ETDEWEB)

    Baker, C.H.; Davis, D.L.; Sutton, E.T.

    1989-03-01

    Superficial fibular nerve stimulation (SFNS) causes increased pre- and post-capillary resistances as well as increased capillary permeability in the dog hind paw. These responses indicate possible adrenergic and histaminergic interactions. The distribution of blood flow between capillaries and arteriovenous anastomoses (AVA) may depend on the relative effects of these neural inputs. Right hind paws of anesthetized heparinized dogs were vascularly and neurally isolated and perfused with controlled pressure. Blood flow distribution was calculated from the venous recovery of 85Sr-labeled microspheres (15 microns). The mean transit times of 131I-albumin and 85Sr-labeled microspheres were calculated. The effects of adrenergic and histaminergic antagonists with and without SFNS were determined. Phentolamine blocked the entire response to SFNS. Prazosin attenuated increases in total and AVA resistance. Yohimbine prevented increased total resistance, attenuated the AVA resistance increase, and revealed a decrease in capillary circuit resistance. Pyrilamine attenuated total resistance increase while SFNS increased capillary and AVA resistances. Metiamide had no effect on blood flow distribution with SFNS. The increase in AVA resistance with SFNS apparently resulted from a combination of alpha 1 and alpha 2 receptor stimulation but not histaminergic effects.

  7. Prediction of Anomalous Blood Viscosity in Confined Shear Flow

    Science.gov (United States)

    Thiébaud, Marine; Shen, Zaiyi; Harting, Jens; Misbah, Chaouqi

    2014-06-01

    Red blood cells play a major role in body metabolism by supplying oxygen from the microvasculature to different organs and tissues. Understanding blood flow properties in microcirculation is an essential step towards elucidating fundamental and practical issues. Numerical simulations of a blood model under a confined linear shear flow reveal that confinement markedly modifies the properties of blood flow. A nontrivial spatiotemporal organization of blood elements is shown to trigger hitherto unrevealed flow properties regarding the viscosity η, namely ample oscillations of its normalized value [η]=(η-η0)/(η0ϕ) as a function of hematocrit ϕ (η0=solvent viscosity). A scaling law for the viscosity as a function of hematocrit and confinement is proposed. This finding can contribute to the conception of new strategies to efficiently detect blood disorders, via in vitro diagnosis based on confined blood rheology. It also constitutes a contribution for a fundamental understanding of rheology of confined complex fluids.

  8. Blood flow dynamics and sensitivity in breasts after reconstruction with DIEP-flap.

    Science.gov (United States)

    Klasson, Stina; Svensson, Karin; Wollmer, Per; Velander, Patrik; Svensson, Henry

    2014-12-01

    A method of breast reconstruction is based on the Deep Inferior Epigastric Perforator (DIEP) technique. Skin and fat are transplanted from the abdomen to the chest; blood vessels are reconnected through microsurgery. Nerves are, however, left unconnected. This study aims to evaluate the blood flow and reinnervation of blood vessels and skin in breasts reconstructed by DIEP flaps without neural repair. In all, DIEP flaps of 10 patients were tested at an average of 16.3 months postoperatively. Blood flow was assessed by PeriScan PIM II System, both before and after indirect heating. Tactile perception threshold was assessed by Semmes-Weinstein monofilament and thermal sensibility by SENSELab MSA Thermotest. The patients' contralateral breasts were used as controls. The blood flow of the flaps was statistically significantly lower than in the control breasts, both before and after indirect heating. The change in blood flow after indirect heating did, however, not significantly differ when comparing the breasts. All flaps regained deep pressure sensibility in all four quadrants. Five patients regained even better sensibility in one of their quadrants. Seven patients regained perception of cold stimuli, five perceived warmth. This study has shown that skin blood flow regulation is present in DIEP flaps 1 year after reconstruction. Blood flow dynamics are very similar to those in the normal breast. There is also a recovery of tactile and thermal sensibility, but this study has not shown any clear parallels between recovery blood flow, tactile sensibility and thermal sensibility.

  9. Renal cortical and medullary blood flow responses to altered NO-availability in humans

    DEFF Research Database (Denmark)

    Damkjaer, Mads; Vafaee, Manoucher; Møller, Michael Lehd;

    2010-01-01

    of one voxel were eliminated stepwise from the external surface of the VOI ('voxel peeling'), and the blood flow subsequently determined in each new, reduced VOI. Blood flow in the shrinking volumes of interest (VOIs) decreased as the number of cycles of voxel peeling increased. After 4-5 cycles, blood...... flow was not reduced further by additional voxel peeling. This volume-insensitive flow was measured to be 2.30 ±0.17 ml·(g·min)(-1) during the control period; it increased during infusion of glyceryl nitrate to 2.97 ±0.18 ml·(g·min)(-1) (p...

  10. Subcutaneous blood flow during insulin-induced hypoglycaemia

    DEFF Research Database (Denmark)

    Hilsted, J; Madsbad, S; Sestoft, L

    1982-01-01

    Subcutaneous blood flow was measured preceding insulin-induced hypoglycaemia, at the onset of hypoglycaemic symptoms and 2 h later in juvenile diabetics with and without autonomic neuropathy and in normal males. In all groups subcutaneous blood flow decreased at the onset of hypoglycaemic symptoms...... compared with pre-hypoglycaemic flow. Two hours after onset of hypoglycaemic symptoms, subcutaneous blood flow was still significantly decreased compared with pre-hypoglycaemic flow. In normal subjects local nerve blockade had no effect on blood flow changes during hypoglycaemia, whereas local alpha......-receptor blockade abolished the vasoconstrictor response. We suggest that circulating catecholamines stimulating vascular alpha-receptors are probably responsible for flow reduction in the subcutaneous tissue during hypoglycaemia....

  11. Pulsatile blood flow in Abdominal Aortic Aneurysms

    Science.gov (United States)

    Salsac, Anne-Virginie; Lasheras, Juan C.; Singel, Soeren; Varga, Chris

    2001-11-01

    We discuss the results of combined in-vitro laboratory measurements and clinical observations aimed at determining the effect that the unsteady wall shear stresses and the pressure may have on the growth and eventual rupturing of an Abdominal Aortic Aneurysm (AAA), a permanent bulging-like dilatation occurring near the aortic bifurcation. In recent years, new non-invasive techniques, such as stenting, have been used to treat these AAAs. However, the development of these implants, aimed at stopping the growth of the aneurysm, has been hampered by the lack of understanding of the effect that the hemodynamic forces have on the growth mechanism. Since current in-vivo measuring techniques lack the precision and the necessary resolution, we have performed measurements of the pressure and shear stresses in laboratory models. The models of the AAA were obtained from high resolution three-dimensional CAT/SCANS performed in patients at early stages of the disease. Preliminary DPIV measurements show that the pulsatile blood flow discharging into the cavity of the aneurysm leads to large spikes of pressure and wall shear stresses near and around its distal end, indicating a possible correlation between the regions of high wall shear stresses and the observed location of the growth of the aneurysm.

  12. Blood Flow Restricted Exercise and Vascular Function

    Directory of Open Access Journals (Sweden)

    Masahiro Horiuchi

    2012-01-01

    Full Text Available It is established that regular aerobic training improves vascular function, for example, endothelium-dependent vasodilatation and arterial stiffness or compliance and thereby constitutes a preventative measure against cardiovascular disease. In contrast, high-intensity resistance training impairs vascular function, while the influence of moderate-intensity resistance training on vascular function is still controversial. However, aerobic training is insufficient to inhibit loss in muscular strength with advancing age; thus, resistance training is recommended to prevent sarcopenia. Recently, several lines of study have provided compelling data showing that exercise and training with blood flow restriction (BFR leads to muscle hypertrophy and strength increase. As such, BFR training might be a novel means of overcoming the contradiction between aerobic and high-intensity resistance training. Although it is not enough evidence to obtain consensus about impact of BFR training on vascular function, available evidences suggested that BFR training did not change coagulation factors and arterial compliance though with inconsistence results in endothelial function. This paper is a review of the literature on the impact of BFR exercise and training on vascular function, such as endothelial function, arterial compliance, or other potential factors in comparison with those of aerobic and resistance training.

  13. Resistance exercise with different volumes: blood pressure response and forearm blood flow in the hypertensive elderly

    Directory of Open Access Journals (Sweden)

    Brito AF

    2014-12-01

    Full Text Available Aline de Freitas Brito,1 Caio Victor Coutinho de Oliveira,2 Maria do Socorro Brasileiro-Santos,1 Amilton da Cruz Santos1 1Physical Education Department, 2Research Laboratory for Physical Training Applied to Performance and Health, Federal University of Paraíba, João Pessoa, Brazil Background: The purpose of this study was to evaluate the effect of two sessions of resistance exercise with different volumes on post-exercise hypotension, forearm blood flow, and forearm vascular resistance in hypertensive elderly subjects.Methods: The study was conducted with ten hypertensive elderly (65±3 years, 28.7±3 kg/m2 subjected to three experimental sessions, ie, a control session, exercise with a set (S1, and exercise with three sets (S3. For each session, the subjects were evaluated before and after intervention. In the pre-intervention period, blood pressure, forearm blood flow, and forearm vascular resistance were measured after 10 minutes of rest in the supine position. Thereafter, the subjects were taken to the gym to perform their exercise sessions or remained at rest during the same time period. Both S1 and S3 comprised a set of ten repetitions of ten exercises, with an interval of 90 seconds between exercises. Subsequently, the measurements were again performed at 10, 30, 50, 70, and 90 minutes of recovery (post-intervention in the supine position.Results: Post-exercise hypotension was greater in S3 than in S1 (systolic blood pressure, −26.5±4.2 mmHg versus −17.9±4.7 mmHg; diastolic blood pressure, −13.8±4.9 mmHg versus −7.7±5 mmHg, P<0.05. Similarly, forearm blood flow and forearm vascular resistance changed significantly in both sessions with an increase and decrease, respectively, that was more evident in S3 than in S1 (P<0.05.Conclusion: Resistance exercises with higher volume were more effective in causing post-exercise hypotension, being accompanied by an increase in forearm blood flow and a reduction of forearm vascular

  14. Blood flow velocity in migraine attacks - a transcranial Doppler study

    Energy Technology Data Exchange (ETDEWEB)

    Zwetsloot, C.P.; Caekebeke, J.F.V.; Jansen, J.C.; Odink, J.; Ferrari, M.D. (Rijksuniversiteit Leiden (Netherlands))

    1991-05-01

    A pulsed Doppler device was used to measure blood flow velocities in the common carotid artery, the extracranial part of the internal carotid artery, the external carotid artery, the middle cerebral artery, and the anterior cerebral artery in 31 migraneurs without aura (n=27) and with aura (n=4), both during and ouside an attack. The aims were to compare blood flow velocity during and between migraine attacks and to study asymmetries of the blood flow velocity. Compared with blood flow velocity values obtained in the attack-free interval, blood flow velocity was lower during attacks without aura in both common carotid arteries, but not in the other extra- and intracranial vessels which were examined. However, during attacks of migraine with aura, blood flow velocity tended to be lower in all examined vessels. There were no asymmetries of the blood flow velocity. It is suggested that during migraine attacks without aura there is a dissociation in blood flow regulation in the common carotid and middle cerebral arteries. 20 refs., 2 tabs.

  15. Blood flow rate measurements with indicator techniques revisited

    DEFF Research Database (Denmark)

    Sejrsen, Per; Bülow, Jens

    2009-01-01

    In view of the emerging role, disturbances in regional blood flow rate seem to play in the pathogenesis of the metabolic syndrome; we review the concepts of the classical indicator dilution and washout techniques used for determinations of regional blood flow rate. Prerequisites, assumptions...

  16. Nephron blood flow dynamics measured by laser speckle contrast imaging

    DEFF Research Database (Denmark)

    von Holstein-Rathlou, Niels-Henrik; Sosnovtseva, Olga V; Pavlov, Alexey N

    2011-01-01

    Tubuloglomerular feedback (TGF) has an important role in autoregulation of renal blood flow and glomerular filtration rate (GFR). Because of the characteristics of signal transmission in the feedback loop, the TGF undergoes self-sustained oscillations in single-nephron blood flow, GFR, and tubula...

  17. N-butyl cyanoacrylate embolization with blood flow control of an arterioportal shunt that developed after radiofrequency ablation of hepatocellular carcinoma

    Energy Technology Data Exchange (ETDEWEB)

    Sonomura, Tetsuo; Kawai, Nobuyuki; Kishi, Kazushi [Wakayama Medical University, Wakayama (Japan); and others

    2014-04-15

    We present a case of a patient with rapid deterioration of esophageal varices caused by portal hypertension accompanied by a large arterioportal shunt that developed after radiofrequency ablation of hepatocellular carcinoma. We used n-butyl cyanoacrylate (NBCA) as an embolic material to achieve pinpoint embolization of the shunt, because the microcatheter tip was 2 cm away from the shunt site. Under hepatic arterial flow control using a balloon catheter, the arterioportal shunt was successfully embolized with NBCA, which caused an improvement in the esophageal varices.

  18. Data adaptive estimation of transversal blood flow velocities

    DEFF Research Database (Denmark)

    Pirnia, E.; Jakobsson, A.; Gudmundson, E.

    2014-01-01

    , posing natural difficulties due to the complex behaviour of blood flow, and due to the natural orientation of most blood vessels. Recently, a transversal modulation scheme was introduced to induce also an oscillation along the transversal direction, thereby allowing for the measurement of also...... the transversal blood flow. In this paper, we propose a novel data-adaptive blood flow estimator exploiting this modulation scheme. Using realistic Field II simulations, the proposed estimator is shown to achieve a notable performance improvement as compared to current state-of-the-art techniques....

  19. Micro-PIV measurements of blood flow in extraembryonic blood vessels of chicken embryos.

    Science.gov (United States)

    Lee, Jung Yeop; Ji, Ho Seong; Lee, Sang Joon

    2007-10-01

    The hemodynamic characteristics of blood flow are important in the diagnosis of circulatory diseases, since such diseases are related to wall shear stress of cardiovascular vessels. In chicken embryos at early stages of development, it is possible to directly visualize blood flow inside blood vessels. We therefore employed a micro-PIV technique to assess blood flow in extraembryonic venous and arterial blood vessels of chicken embryos, using red blood cells (RBCs) as tracers and obtaining flow images of RBCs using a high-speed CMOS camera. The mean velocity field showed non-Newtonian flow characteristics. The blood flow in two venous vessels merged smoothly into the Y-shaped downstream vein without any flow separation or secondary flow. Vorticity was high in the inner regions, where the radius of curvature varied greatly. A periodic variation of temporally resolved velocity signals, due to beating of the heart, was observed in arterial blood vessels. The pulsating frequency was obtained by fast Fourier transform analysis using the measured velocity data. The measurement technique used here was useful in analyzing the hemodynamic characteristics of in vivo blood flow in chicken embryos.

  20. Exploration of 4D MRI blood flow using stylistic visualization.

    Science.gov (United States)

    van Pelt, Roy; Oliván Bescós, Javier; Breeuwer, Marcel; Clough, Rachel E; Gröller, M Eduard; ter Haar Romenij, Bart; Vilanova, Anna

    2010-01-01

    Insight into the dynamics of blood-flow considerably improves the understanding of the complex cardiovascular system and its pathologies. Advances in MRI technology enable acquisition of 4D blood-flow data, providing quantitative blood-flow velocities over time. The currently typical slice-by-slice analysis requires a full mental reconstruction of the unsteady blood-flow field, which is a tedious and highly challenging task, even for skilled physicians. We endeavor to alleviate this task by means of comprehensive visualization and interaction techniques. In this paper we present a framework for pre-clinical cardiovascular research, providing tools to both interactively explore the 4D blood-flow data and depict the essential blood-flow characteristics. The framework encompasses a variety of visualization styles, comprising illustrative techniques as well as improved methods from the established field of flow visualization. Each of the incorporated styles, including exploded planar reformats, flow-direction highlights, and arrow-trails, locally captures the blood-flow dynamics and may be initiated by an interactively probed vessel cross-section. Additionally, we present the results of an evaluation with domain experts, measuring the value of each of the visualization styles and related rendering parameters.

  1. Loss of autoregulation of blood flow in subcutaneous tissue in juvenile diabetes

    DEFF Research Database (Denmark)

    Henriksen, O; Kastrup, J; Parving, H H;

    1984-01-01

    and retinopathy. The blood flow remained constant in all normal subjects, when the arterial perfusion pressure was varied between 70 and 150 mm Hg. All diabetics had impaired or reduced autoregulation of the subcutaneous blood flow. The blood flow increased and decreased almost linearly with the changes...... in arterial perfusion pressure. The mechanism underlying the defect autoregulation of blood flow in diabetics is uncertain; possibilities include structural changes of the arterioles and/or alterations of local metabolic factors.......The autoregulation of blood flow in subcutaneous tissue was investigated at the level of the lateral malleolus by the local 133Xenon washout technique. We have investigated eight long-term insulin-dependent diabetics and seven healthy controls. All diabetics had moderate diabetic nephropathy...

  2. Mechanisms of temporal variation in single-nephron blood flow in rats

    DEFF Research Database (Denmark)

    Yip, K P; Holstein-Rathlou, N H; Marsh, D J

    1993-01-01

    Modified laser-Doppler velocimetry was used to determine the number of different mechanisms regulating single-nephron blood flow. Two oscillations were identified in star vessel blood flow, one at 20-50 mHz and another at 100-200 mHz. Tubuloglomerular feedback (TGF) mediates the slower oscillation......, and the faster one is probably myogenic in origin. Acute hypertension increased autospectral power in the 20-50 mHz and 100-200 mHz frequency bands to 282 +/- 50 and 248 +/- 64%, respectively, of control even though mean single-nephron blood flow was autoregulated. Mean blood flow increased 24.6 +/- 6.1% when...... components in efferent arteriole blood flow....

  3. Lattice BGK Simulations of the Blood Flow in Elastic Vessels

    Institute of Scientific and Technical Information of China (English)

    LU Xiao-Yang; YI Hou-Hui; CHEN Ji-Yao; FANG Hai-Ping

    2006-01-01

    @@ The lattice Boltzmann method is applied to study the flow in elastic blood vessels. The volume-flow rate increases considerably when the compliance constant of the blood vessel is below a critical value. There is a region of the compliance constant in which the average volume-flow rate is dramatically enhanced. A harmonic perturbation of the pressure does not change the behaviour of the average volume-flow rate while the harmonic wave attenuates very quickly along the tube when the resonant period is close to that of the input wave. The model, together with the simulation results, is expected to be helpful to understand the mechanism of the blood volume-flow rate related to the compliance constant of the blood vessel, especially on the dependence of the flux of human blood vessel under weather changes, which has medical significance.

  4. Mammary blood flow regulation in the nursing rabbit

    Energy Technology Data Exchange (ETDEWEB)

    Katz, M.; Creasy, R.K.

    1984-11-01

    Cardiac output and mammary blood flow distribution prior to and after suckling were studied in 10 nursing rabbits by means of radionuclide-labeled microspheres. Suckling was followed by a 5.8% rise in cardiac output and a 20.4% rise in mammary blood flow. Determinations of intraglandular blood flow distribution have shown that there was a 43% increase in blood flow to the glands suckled from as compared to a 22.7% rise to the contralateral untouched glands and a 4.9% rise in the remainder of untouched glands. The conclusion is that a local mechanism may be involved in the regulation of mammary blood flow in the nursing rabbit.

  5. Ultrasonic Doppler measurement of renal artery blood flow

    Science.gov (United States)

    Freund, W. R.; Beaver, W. L.; Meindl, J. D.

    1976-01-01

    Studies were made of (1) blood flow redistribution during lower body negative pressure (LBNP), (2) the profile of blood flow across the mitral annulus of the heart (both perpendicular and parallel to the commissures), (3) testing and evaluation of a number of pulsed Doppler systems, (4) acute calibration of perivascular Doppler transducers, (5) redesign of the mitral flow transducers to improve reliability and ease of construction, and (6) a frequency offset generator designed for use in distinguishing forward and reverse components of blood flow by producing frequencies above and below the offset frequency. Finally methodology was developed and initial results were obtained from a computer analysis of time-varying Doppler spectra.

  6. PERFORMANCE MODELING AND ANALYSIS OF BLOOD FLOW IN ELASTIC ARTERIES

    Institute of Scientific and Technical Information of China (English)

    Anil Kumar; C.L. Varshney; G.C. Sharma

    2005-01-01

    Two different non-Newtonian models for blood flow are considered, first a simple power law model displaying shear thinning viscosity, and second a generalized Maxwell model displaying both shear thinning viscosity and oscillating flow viscous-elasticity. These models are used along with a Newtonian model to study sinusoidal flow of blood in rigid and elastic straight arteries in the presence of magnetic field. The elasticity of blood does not appear to influence its flow behavior under physiological conditions in the large arteries,purely viscous shear thinning model should be quite realistic for simulating blood flow under these conditions. On using the power law model with high shear rate for sinusoidal flow simulation in elastic arteries, the mean and amplitude of the flow rate were found to be lower for a power law fluid compared to Newtonian fluid for the same pressure gradient. The governing equations have been solved by Crank-Niclson scheme. The results are interpreted in the context of blood in the elastic arteries keeping the magnetic effects in view. For physiological flow simulation in the aorta, an increase in mean wall shear stress, but a reduction in peak wall shear stress were observed for power law model compared to a Newtonian fluid model for matched flow rate wave form. Blood flow in the presence of transverse magnetic field in an elastic artery is investigated and the influence of factors such as morphology and surface irregularity is evaluated.

  7. Alterations of Regional Cerebral Blood Flow in Major Depressive Disorder

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Won Hyoung; Chung, Yong An; Seo, Ye Young; Yoo, Ik Dong; Na, Sae Jung; Jung, Hyun Suk; Kim, Ki Jun [College of Medicine, The Catholic University of Korea, Seoul (Korea, Republic of)

    2009-04-15

    The authors analyzed how the regional cerebral blood flow (rCBF) findings of patients with major depression differ from the normal control, and our results were compared to previous reports. Twelve patients fulfilling DSM-IV criteria for major depression who were off all psychotropic medications for > 4 weeks (male: 7, female: 5, age range: 19approx52 years, average age: 29.3+-9.9 years) and 14 normal volunteers (male: 8, female: 6, age range: 19approx53 years, average age: 31.4+-9.2 years) were recruited. Images of brain perfusion SPECT were obtained using Tc-99m ECD and patterns of the rCBF were compared between patients with major depression and the healthy control subjects. The patients with major depression showed increase of the r-CBF in right lingual gyrus, right fusiform gyrus, left lingual gyrus, left precuneus, and left superior temporal gyrus, and showed decrease of r-CBF in right pons, left medial frontal gyrus, cingulate gyrus of left limbic lobe, cingulate gyrus of right frontal lobe, and cingulate gyrus of right limbic lobe compared to the normal control. The Tc-99m ECD brain perfusion SPECT findings in our study did not differ from the previously reported regional cerebral blood flow pattern of patients with major depression. Especially, decreased rCBF pattern typical to major depression patients in the right pons, left medial frontal gyrus, and cingulate regions was clearly demonstrated

  8. Dynamics of blood flow in a microfluidic ladder network

    Science.gov (United States)

    Maddala, Jeevan; Zilberman-Rudenko, Jevgenia; McCarty, Owen

    The dynamics of a complex mixture of cells and proteins, such as blood, in perturbed shear flow remains ill-defined. Microfluidics is a promising technology for improving the understanding of blood flow under complex conditions of shear; as found in stent implants and in tortuous blood vessels. We model the fluid dynamics of blood flow in a microfluidic ladder network with dimensions mimicking venules. Interaction of blood cells was modeled using multiagent framework, where cells of different diameters were treated as spheres. This model served as the basis for predicting transition regions, collision pathways, re-circulation zones and residence times of cells dependent on their diameters and device architecture. Based on these insights from the model, we were able to predict the clot formation configurations at various locations in the device. These predictions were supported by the experiments using whole blood. To facilitate platelet aggregation, the devices were coated with fibrillar collagen and tissue factor. Blood was perfused through the microfluidic device for 9 min at a physiologically relevant venous shear rate of 600 s-1. Using fluorescent microscopy, we observed flow transitions near the channel intersections and at the areas of blood flow obstruction, which promoted larger thrombus formation. This study of integrating model predictions with experimental design, aids in defining the dynamics of blood flow in microvasculature and in development of novel biomedical devices.

  9. Nutraceuticals for blood pressure control.

    Science.gov (United States)

    Sirtori, Cesare R; Arnoldi, Anna; Cicero, Arrigo F G

    2015-01-01

    Significant effects on blood pressure (BP) have been reported from large nutritional interventions, particularly the Dietary Approaches to Stop Hypertension (DASH) and the Mediterranean diet. In more recent years, numerous studies have investigated the possible BP-lowering effect of different nutraceuticals; these range from specific foods to minerals, lipids, whole proteins, peptides, amino acids, probiotics, and vitamins. While a very large body of evidence supports the use of potassium, L-arginine, vitamins C and D, cocoa flavonoids, beetroot juice, some probiotics, coenzyme Q10, controlled-release melatonin, aged garlic extract, and coffee, the use of other nutraceuticals, such as green tea, flaxseed, and resveratrol, has not as yet been supported by adequate evidence. In some cases, e.g. proteins/peptides, the responsible component needs also to be fully uncovered. Finally, while for most of the products only short-term studies are available, with no specific end-points, an ongoing very large prospective study on chocolate flavanols will answer the question whether this may reduce cardiovascular risk. Thus, in addition to data on long-term safety, further clinical research is advisable in order to identify, among active nutraceuticals, those with the best cost-effectiveness and risk-benefit ratio for a wide use in the general population with a raised cardiovascular risk consequent to uncomplicated hypertension.

  10. Cerebral blood flow and metabolism during sleep.

    Science.gov (United States)

    Madsen, P L; Vorstrup, S

    1991-01-01

    A review of the current literature regarding sleep-induced changes in cerebral blood flow (CBF) and cerebral metabolic rate (CMR) is presented. Early investigations have led to the notion that dreamless sleep was characterized by global values of CBF and CMR practically at the level of wakefulness, while rapid eye movement (REM) sleep (dream sleep) was a state characterized by a dramatically increased level of CBF and possibly also of CMR. However, recent investigations firmly contradict this notion. Investigations on CBF and CMR performed during non-REM sleep, taking the effect of different levels of sleep into consideration, show that light sleep (stage II) is characterized by global levels of CBF and CMR only slightly reduced by 3-10% below the level associated with wakefulness, whereas CBF and CMR during deep sleep (stage III-IV) is dramatically reduced by 25-44%. Furthermore, recent data indicate that global levels of CBF and CMR are about the same during REM sleep as in wakefulness. On the regional level, deep sleep seems to be associated with a uniform decrease in regional CBF and CMR. Investigations concerning regional CBF and CMR during REM sleep are few but data from recent investigations seem to identify site-specific changes in regional CBF and CMR during REM sleep. CBF and CMR are reflections of cerebral synaptic activity and the magnitude of reduction in these variables associated with deep sleep indicates that overall cerebral synaptic activity is reduced to approximately one-half the level associated with wakefulness, while cerebral synaptic activity levels during REM sleep are similar to wakefulness. However, even though the new understanding of CBF and CMR during sleep provides significant and important information of the brain's mode of working during sleep, it does not at its current state identify the physiological processes involved in sleep or the physiological role of sleep.

  11. Regional patterns of cortical blood flow distinguish extraverts from introverts

    OpenAIRE

    Stenberg, Georg; Risberg, Jarl; Warkentin, S.; Rosén, Ingmar

    1990-01-01

    Eysenck's hypothesis of higher cortical arousal in introverts was examined using regional cerebral blood flow measurement in 37 healthy subjects . The measurement was made at rest, using the133Xe-inhalation method. Estimates of gray matter flow were obtained for 32 brain regions. There was no significant evidence of personality differences in general arousal, as measured by the mean flow level, averaged over all regions. There were, however, regional differences. An overall test of the blood ...

  12. Quantification of complex blood flow using real-time in vivo vector flow ultrasound

    DEFF Research Database (Denmark)

    Pedersen, Mads Møller; Pihl, Michael Johannes; Haugaard, Per;

    2010-01-01

    A quantitative method for distinguishing complex from non-complex flow patterns in ultrasound is presented. A new commercial BK Medical ultrasound scanner uses the Transverse Oscillation vector flow technique for visualising flow patterns in real-time. In vivo vector flow data of the blood flow...

  13. On the flow dependency of the electrical conductivity of blood

    NARCIS (Netherlands)

    Hoetink, AE; Faes, TJC; Visser, KR; Heethaar, RM

    2004-01-01

    Experiments presented in the literature show that the electrical conductivity of flowing blood depends on flow velocity. The aim of this study is to extend the Maxwell-Fricke theory, developed for a dilute suspension of ellipsoidal particles in an electrolyte, to explain this flow dependency of the

  14. ANALYSIS OF PULSATILE BLOOD FLOW IN AXIALLY MOVING ARTERIES

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In order to study motional properties of pulsatile blood flow in axially moving arteries, the authors derived some expressions of the pulsatile blood flow from the basic equations of motion for blood and vascular walls, including an axial blood velocity equation, a flow rate equation and a wall shear stress equation, which described not only the overall axial movement of the arteries but also the elastic properties of the vascular walls, discussed the effects of the arterial wall elasticity on the wall shear stress in coronary arteries in terms of these expressions, and analyzed changes of motional properties of pulsatile blood flow between an elastic arterial tube model and a rigid tube model. The results proved the inference by J.E. Moore Jr. et al. (1994) that the axial movement of arteries be as important in determining coronary artery hemodynamics as the elastic property of the vascular wall.

  15. Mesenteric, coeliac and splanchnic blood flow in humans during exercise

    DEFF Research Database (Denmark)

    Perko, M J; Nielsen, H B; Skak, C;

    1998-01-01

    1. Exercise reduces splanchnic blood flow, but the mesenteric contribution to this response is uncertain. 2. In nineteen humans, superior mesenteric and coeliac artery flows were determined by duplex ultrasonography during fasting and postprandial submaximal cycling and compared with the splanchnic...... blood flow as assessed by the Indocyanine Green dye-elimination technique. 3. Cycling increased arterial pressure, heart rate and cardiac output, while it reduced total vascular resistance. These responses were not altered in the postprandial state. During fasting, cycling increased mesenteric, coeliac...... and splanchnic resistances by 76, 165 and 126 %, respectively, and it reduced corresponding blood flows by 32, 50 and 43 % (by 0.18 +/- 0.04, 0.42 +/- 0.03 and 0.60 +/- 0.04 l min-1). Postprandially, mesenteric and splanchnic vascular resistances decreased, thereby elevating regional blood flow, while...

  16. Effects of non Newtonian spiral blood flow through arterial stenosis

    Science.gov (United States)

    Hasan, Md. Mahmudul; Maruf, Mahbub Alam; Ali, Mohammad

    2016-07-01

    The spiral component of blood flow has both beneficial and detrimental effects in human circulatory system. A numerical investigation is carried out to analyze the effect of spiral blood flow through an axisymmetric three dimensional artery having 75% stenosis at the center. Blood is assumed as a Non-Newtonian fluid. Standard k-ω model is used for the simulation with the Reynolds number of 1000. A parabolic velocity profile with spiral flow is used as inlet boundary condition. The peak values of all velocity components are found just after stenosis. But total pressure gradually decreases at downstream. Spiral flow of blood has significant effects on tangential component of velocity. However, the effect is mild for radial and axial velocity components. The peak value of wall shear stress is at the stenosis zone and decreases rapidly in downstream. The effect of spiral flow is significant for turbulent kinetic energy. Detailed investigation and relevant pathological issues are delineated throughout the paper.

  17. Modified Beer-Lambert law for blood flow

    Science.gov (United States)

    Baker, Wesley B.; Parthasarathy, Ashwin B.; Busch, David R.; Mesquita, Rickson C.; Greenberg, Joel H.; Yodh, A. G.

    2015-03-01

    The modified Beer-Lambert law is among the most widely used approaches for analysis of near-infrared spectroscopy (NIRS) reflectance signals for measurements of tissue blood volume and oxygenation. Briefly, the modified Beer-Lambert paradigm is a scheme to derive changes in tissue optical properties based on continuous-wave (CW) diffuse optical intensity measurements. In its simplest form, the scheme relates differential changes in light transmission (in any geometry) to differential changes in tissue absorption. Here we extend this paradigm to the measurement of tissue blood flow by diffuse correlation spectroscopy (DCS). In the new approach, differential changes of the intensity temporal auto-correlation function at a single delay-time are related to differential changes in blood flow. The key theoretical results for measurement of blood flow changes in any tissue geometry are derived, and we demonstrate the new method to monitor cerebral blood flow in a pig under conditions wherein the semi-infinite geometry approximation is fairly good. Specifically, the drug dinitrophenol was injected in the pig to induce a gradual 200% increase in cerebral blood flow, as measured with MRI velocity flow mapping and by DCS. The modified Beer-Lambert law for flow accurately recovered these flow changes using only a single delay-time in the intensity auto-correlation function curve. The scheme offers increased DCS measurement speed of blood flow. Further, the same techniques using the modified Beer-Lambert law to filter out superficial tissue effects in NIRS measurements of deep tissues can be applied to the DCS modified Beer-Lambert law for blood flow monitoring of deep tissues.

  18. AN ANALYSIS MODEL OF PULSATILE BLOOD FLOW IN ARTERIES

    Institute of Scientific and Technical Information of China (English)

    LIUZhao-rong; XUGang; CHENYong; TENGZhong0=zhao; QINKai-rong

    2003-01-01

    Blood flow in artery was treated as the flow under equilibriums state(the steady flow under mean pressure)combined with the periodically small pulsatile flow.Using vascular strain energy function advanced by Fung,the vascular stress-strain relationship under equilibrium state was analyzed and the circumferential and axial elastic moduli were deduced that are expressed while the arterial strains around the equilibrium state are relatively small,so that the equations of vesse wall motion under the pulsatile pressure could be established here.Through solving both the vessel equations and the linear Navier-Stokes equations,the analytic expressions of the blood flow velocities and the vascular displacements were obtained.The influence of the difference between vascular circumferentia and axial elasticities on pulsatile blood flow and vascular motion was discussed in details.

  19. AN ANALYSIS MODEL OF PULSATILE BLOOD FLOW IN ARTERIES

    Institute of Scientific and Technical Information of China (English)

    柳兆荣; 徐刚; 陈泳; 滕忠照; 覃开蓉

    2003-01-01

    Blood flow in artery was treated as the flow under equilibrium state ( the steady flow under mean pressure ) combined with the periodically small pulsatile flow. Using vascular strain energy function advanced by Fung, the vascular stress-strain relationship under equilibrium state was analyzed and the circumferential and axial elastic moduli were deduced that are expressed while the arterial strains around the equilibrium state are relatively small, so that the equations of vessel wall motion under the pulsatile pressure could be established here. Through solving both the vessel equations and the linear NavierStokes equations, the analytic expressions of the blood flow velocities and the vascular displacements were obtained. The influence of the difference between vascular circumferential and axial elasticities on pulsatile blood flow and vascular motion was discussed in details.

  20. Arterial secondary blood flow patterns visualized with vector flow ultrasound

    DEFF Research Database (Denmark)

    Pedersen, Mads Møller; Pihl, Michael Johannes; Hansen, Jens Munk

    2011-01-01

    This study presents the first quantification and visualisation of secondary flow patterns with vector flow ultrasound. The first commercial implementation of the vector flow method Transverse Oscillation was used to obtain in-vivo, 2D vector fields in real-time. The hypothesis of this study...

  1. Regulation of exercise blood flow: Role of free radicals.

    Science.gov (United States)

    Trinity, Joel D; Broxterman, Ryan M; Richardson, Russell S

    2016-09-01

    During exercise, oxygen and nutrient rich blood must be delivered to the active skeletal muscle, heart, skin, and brain through the complex and highly regulated integration of central and peripheral hemodynamic factors. Indeed, even minor alterations in blood flow to these organs have profound consequences on exercise capacity by modifying the development of fatigue. Therefore, the fine-tuning of blood flow is critical for optimal physical performance. At the level of the peripheral circulation, blood flow is regulated by a balance between the mechanisms responsible for vasodilation and vasoconstriction. Once thought of as toxic by-products of in vivo chemistry, free radicals are now recognized as important signaling molecules that exert potent vasoactive responses that are dependent upon the underlying balance between oxidation-reduction reactions or redox balance. Under normal healthy conditions with low levels of oxidative stress, free radicals promote vasodilation, which is attenuated with exogenous antioxidant administration. Conversely, with advancing age and disease where background oxidative stress is elevated, an exercise-induced increase in free radicals can further shift the redox balance to a pro-oxidant state, impairing vasodilation and attenuating blood flow. Under these conditions, exogenous antioxidants improve vasodilatory capacity and augment blood flow by restoring an "optimal" redox balance. Interestingly, while the active skeletal muscle, heart, skin, and brain all have unique functions during exercise, the mechanisms by which free radicals contribute to the regulation of blood flow is remarkably preserved across each of these varied target organs.

  2. Quantitative myocardial blood flow with Rubidium-82 PET

    DEFF Research Database (Denmark)

    Hagemann, Christoffer E; Ghotbi, Adam A; Kjær, Andreas

    2015-01-01

    Positron emission tomography (PET) allows assessment of myocardial blood flow in absolute terms (ml/min/g). Quantification of myocardial blood flow (MBF) and myocardial flow reserve (MFR) extend the scope of conventional semi-quantitative myocardial perfusion imaging (MPI): e.g. in 1......) identification of the extent of a multivessel coronary artery disease (CAD) burden, 2) patients with balanced 3-vessel CAD, 3) patients with subclinical CAD, and 4) patients with regional flow variance, despite of a high global MFR. A more accurate assessment of the ischemic burden in patients with intermediate...

  3. Optimal Power Flow Control by Rotary Power Flow Controller

    Directory of Open Access Journals (Sweden)

    KAZEMI, A.

    2011-05-01

    Full Text Available This paper presents a new power flow model for rotary power flow controller (RPFC. RPFC injects a series voltage into the transmission line and provides series compensation and phase shifting simultaneously. Therefore, it is able to control the transmission line impedance and the active power flow through it. An RPFC is composed mainly of two rotary phase shifting transformers (RPST and two conventional (series and shunt transformers. Structurally, an RPST consists of two windings (stator and rotor windings. The rotor windings of the two RPSTs are connected in parallel and their stator windings are in series. The injected voltage is proportional to the vector sum of the stator voltages and so its amplitude and angle are affected by the rotor position of the two RPSTs. This paper, describes the steady state operation and single-phase equivalent circuit of the RPFC. Also in this paper, a new power flow model, based on power injection model of flexible ac transmission system (FACTS controllers, suitable for the power flow analysis is introduced. Proposed model is used to solve optimal power flow (OPF problem in IEEE standard test systems incorporating RPFC and the optimal settings and location of the RPFC is determined.

  4. Large-Eddy simulation of pulsatile blood flow.

    Science.gov (United States)

    Paul, Manosh C; Mamun Molla, Md; Roditi, Giles

    2009-01-01

    Large-Eddy simulation (LES) is performed to study pulsatile blood flow through a 3D model of arterial stenosis. The model is chosen as a simple channel with a biological type stenosis formed on the top wall. A sinusoidal non-additive type pulsation is assumed at the inlet of the model to generate time dependent oscillating flow in the channel and the Reynolds number of 1200, based on the channel height and the bulk velocity, is chosen in the simulations. We investigate in detail the transition-to-turbulent phenomena of the non-additive pulsatile blood flow downstream of the stenosis. Results show that the high level of flow recirculation associated with complex patterns of transient blood flow have a significant contribution to the generation of the turbulent fluctuations found in the post-stenosis region. The importance of using LES in modelling pulsatile blood flow is also assessed in the paper through the prediction of its sub-grid scale contributions. In addition, some important results of the flow physics are achieved from the simulations, these are presented in the paper in terms of blood flow velocity, pressure distribution, vortices, shear stress, turbulent fluctuations and energy spectra, along with their importance to the relevant medical pathophysiology.

  5. In vivo lateral blood flow velocity measurement using speckle size estimation.

    Science.gov (United States)

    Xu, Tiantian; Hozan, Mohsen; Bashford, Gregory R

    2014-05-01

    In previous studies, we proposed blood measurement using speckle size estimation, which estimates the lateral component of blood flow within a single image frame based on the observation that the speckle pattern corresponding to blood reflectors (typically red blood cells) stretches (i.e., is "smeared") if blood flow is in the same direction as the electronically controlled transducer line selection in a 2-D image. In this observational study, the clinical viability of ultrasound blood flow velocity measurement using speckle size estimation was investigated and compared with that of conventional spectral Doppler of carotid artery blood flow data collected from human patients in vivo. Ten patients (six male, four female) were recruited. Right carotid artery blood flow data were collected in an interleaved fashion (alternating Doppler and B-mode A-lines) with an Antares Ultrasound Imaging System and transferred to a PC via the Axius Ultrasound Research Interface. The scanning velocity was 77 cm/s, and a 4-s interval of flow data were collected from each subject to cover three to five complete cardiac cycles. Conventional spectral Doppler data were collected simultaneously to compare with estimates made by speckle size estimation. The results indicate that the peak systolic velocities measured with the two methods are comparable (within ±10%) if the scan velocity is greater than or equal to the flow velocity. When scan velocity is slower than peak systolic velocity, the speckle stretch method asymptotes to the scan velocity. Thus, the speckle stretch method is able to accurately measure pure lateral flow, which conventional Doppler cannot do. In addition, an initial comparison of the speckle size estimation and color Doppler methods with respect to computational complexity and data acquisition time indicated potential time savings in blood flow velocity estimation using speckle size estimation. Further studies are needed for calculation of the speckle stretch method

  6. Reduced myocardial blood flow in acute and chronic digitalization.

    Science.gov (United States)

    Steiness, E; Bille-Brahe, N E; Hansen, J F; Lomholt, N; Ring-Larsen, H

    1978-07-01

    The myocardial blood flow was measured by the 133Xenon disappearance curve from the left ventricular wall following an injection of 133Xenon in the left coronary artery in 8 dogs without digoxin pretreatment and in 8 chronically digitalized dogs. The myocardial blood flow was significantly less (30%) in the digitalized dogs than in the dogs without pretreatment. In the digitalized dogs as well as in those without pretreatment an intravenous injection of digoxin resulted in a further significant decrease of the myocardial blood flow of about 20% and a significant increase of the coronary vascular resistance. The reduced myocardial blood flow both during acute and chronic digitalization is beleived to be of clinical importance.

  7. Skeletal Blood Flow in Bone Repair and Maintenance

    Institute of Scientific and Technical Information of China (English)

    Ryan E.Tomlinson; Matthew J.Silva

    2013-01-01

    Bone is a highly vascularized tissue, although this aspect of bone is often overlooked. In this article, the importance of blood flow in bone repair and regeneration will be reviewed. First, the skeletal vascular anato-my, with an emphasis on long bones, the distinct mechanisms for vascularizing bone tissue, and methods for remodeling existing vasculature are discussed. Next, techniques for quantifying bone blood flow are briefly summarized. Finally, the body of experimental work that demonstrates the role of bone blood flow in fracture healing, distraction osteogenesis, osteoporosis, disuse osteopenia, and bone grafting is examined. These results illustrate that adequate bone blood flow is an important clinical consideration, particularly during bone regeneration and in at-risk patient groups.

  8. Study Links Stuttering to Less Blood Flow in Brain

    Science.gov (United States)

    ... medlineplus.gov/news/fullstory_162922.html Study Links Stuttering to Less Blood Flow in Brain The more ... to speech may put people at risk for stuttering, a small study suggests. There are also signs ...

  9. Role of cerebral blood flow in extreme breath holding

    Directory of Open Access Journals (Sweden)

    Bain Anthony R.

    2016-01-01

    Full Text Available The role of cerebral blood flow (CBF on a maximal breath-hold (BH in ultra-elite divers was examined. Divers (n = 7 performed one control BH, and one BH following oral administration of the non-selective cyclooxygenase inhibitor indomethacin (1.2 mg/kg. Arterial blood gases and CBF were measured prior to (baseline, and at BH termination. Compared to control, indomethacin reduced baseline CBF and cerebral delivery of oxygen (CDO2 by about 26% (p < 0.01. Indomethacin reduced maximal BH time from 339 ± 51 to 319 ± 57 seconds (p = 0.04. In both conditions, the CDO2 remained unchanged from baseline to the termination of apnea. At BH termination, arterial oxygen tension was higher following oral administration of indomethacin compared to control (4.05 ± 0.45 vs. 3.44 ± 0.32 kPa. The absolute increase in CBF from baseline to the termination of apnea was lower with indomethacin (p = 0.01. These findings indicate that the impact of CBF on maximal BH time is likely attributable to its influence on cerebral H+ washout, and therefore central chemoreceptive drive to breathe, rather than to CDO2.

  10. Short-term glucosamine infusion increases islet blood flow in anesthetized rats.

    Science.gov (United States)

    Gao, Xiang; Jansson, Leif; Persson, A Erik G; Sandberg, Monica

    2013-01-01

    Impaired glucose tolerance and type 2 diabetes in rodents are associated with increased islet blood flow. If this is important for modulation of the endocrine function is at present unknown. We evaluated if glucosamine infusion, which induces peripheral insulin resistance and glucose intolerance, could be used to acutely increase islet blood flow. We infused anaesthetized Sprague-Dawley rats for 2 h with glucosamine (6 mg/kg body weight), in some cases followed by glucose administration. The former induced a 2-fold increase in serum insulin concentrations while plasma glucose remained unchanged. In vitro an augmented insulin response to hyperglycemia and decreased insulin content in batch type islet incubations with glucosamine for 24 h were seen. After 2 h glucosamine exposure in vitro, insulin release was decreased. In vivo glucosamine infusion increased islet blood flow, without affecting other regional blood flow values. Glucose increased islet blood flow to the same extent in control and glucosamine-infused rats. When exposed to 10 mmol/L glucosamine arterioles of isolated perfused islets showed a 10% dilation of their vascular smooth muscle. Thus, application of this model leads to acute hyperinsulinemia in vivo but a decreased insulin release in vitro, which suggests that effects not located to β cells are responsible for the effects seen in vivo. An increased islet blood flow in previously healthy animals was also seen after glucose administration, which can be used to further dissect the importance of blood flow changes in islet function.

  11. The effects of fenoldopam on coronary conduit blood flow after coronary artery bypass graft surgery.

    LENUS (Irish Health Repository)

    Halpenny, M

    2012-02-03

    OBJECTIVE: To quantify the effects of fenoldopam, 0.1 microg\\/kg\\/min, on left internal mammary artery (LIMA) and saphenous vein blood flow after coronary anastomosis. DESIGN: Prospective, randomized, double-blind, placebo-controlled trial. SETTING: University teaching hospital, single institution. PARTICIPANTS: Thirty-one American Society of Anesthesiologists III patients undergoing elective coronary revascularization. INTERVENTIONS: A perivascular ultrasonic flow probe (Linton Instrumentation, Norfolk, UK) was placed around the LIMA and saphenous vein graft after coronary anastomosis. MEASUREMENTS AND MAIN RESULTS: Immediately before and at 5-minute intervals for 15 minutes after starting the infusion, blood flow was measured in the LIMA and one saphenous vein graft using a transit time ultrasonic flow probe. Heart rate, blood pressure, and central venous pressure were documented at these time points. Administration of fenoldopam, 0.1 microg\\/kg\\/min, did not alter heart rate or blood pressure. A small, nonsignificant increase in LIMA blood flow occurred during the 15-minute study period (30 +\\/- 12 to 35 +\\/- 10 mL\\/min) in patients who received fenoldopam. No significant changes occurred in the placebo group. CONCLUSIONS: The findings indicate that fenoldopam, 0.1 microg\\/kg\\/min, did not influence coronary conduit blood flow to a clinically significant extent. The small increase in LIMA blood flow may be of greater importance in high-risk patients or in the prevention of coronary arterial spasm.

  12. Current Imaging Modalities for assessing Ocular Blood Flow in Glaucoma

    OpenAIRE

    Mohindroo, Chirayu; Ichhpujani, Parul; Kumar, Suresh

    2016-01-01

    Glaucoma may be caused by an interplay of elevated intraocular pressure (IOP), vascular, genetic, anatomical, brain, and immune factors. The direct assessment of ocular hemodynam-ics offers promise for glaucoma detection, differentiation, and possibly new treatment modalities. All the methods currently in use to measure ocular blood flow have inherent limitations and measure different aspects of ocular blood flow. This review article attempts to provide detailed information on ocular perfu-si...

  13. Experimental comparison of mammalian and avian blood flow in microchannels

    Science.gov (United States)

    Fink, Kathryn; Liepmann, Dorian

    2015-11-01

    The non-Newtonian, shear rate dependent behavior of blood in microchannel fluid dynamics has been studied for nearly a century, with a significant focus on the characteristics of human blood. However, for over 200 years biologists have noted significant differences in red blood cell characteristics across vertebrate species, with particularly drastic differences in cell size and shape between mammals and non-mammalian classes. We present an experimental analysis of flow in long microchannels for several varieties of mammalian and avian blood, across a range of hematocrits, channel diameters, and flow rates. Correlation of shear rate and viscosity is compared to existing constitutive equations for human blood to further quantify the importance of red blood cell characteristics. Ongoing experimental results are made available in an online database for reference or collaboration. K.F. acknowledges funding from the ARCS Foundation and an NSF Graduate Research Fellowship through NSF Grant DGE 1106400.

  14. APPLICATION OF THE THEORY OF INTERACTING CONTINUA TO BLOOD FLOW

    Energy Technology Data Exchange (ETDEWEB)

    Massoudi, Mehrdad; Kim, Jeongho; Hund, Samuel J.; Antaki, James F.

    2011-01-01

    Micro-scale investigations of the flow and deformation of blood and its formed elements have been studied for many years. Early in vitro investigations in the rotational viscometers or small glass tubes revealed important rheological properties such as the reduced blood apparent viscosity, Fahraeus effect and Fahraeus-Lindqvist effect [1], exhibiting the nonhomogeneous property of blood in microcirculation. We have applied Mixture Theory, also known as Theory of Interacting Continua, to study and model this property of blood [2, 3]. This approach holds great promise for predicting the trafficking of RBCs in micro-scale flows (such as the depletion layer near the wall), and other unique hemorheological phenomena relevant to blood trauma. The blood is assumed to be composed of an RBC component modeled as a nonlinear fluid, suspended in plasma, modeled as a linearly viscous fluid.

  15. Blood flow changes coincide with cellular rearrangements during blood vessel pruning in zebrafish embryos.

    Directory of Open Access Journals (Sweden)

    Eva Kochhan

    Full Text Available After the initial formation of a highly branched vascular plexus, blood vessel pruning generates a hierarchically structured network with improved flow characteristics. We report here on the cellular events that occur during the pruning of a defined blood vessel in the eye of developing zebrafish embryos. Time-lapse imaging reveals that the connection of a new blood vessel sprout with a previously perfused multicellular endothelial tube leads to the formation of a branched, Y-shaped structure. Subsequently, endothelial cells in parts of the previously perfused branch rearrange from a multicellular into a unicellular tube, followed by blood vessel detachment. This process is accompanied by endothelial cell death. Finally, we show that differences in blood flow between neighboring vessels are important for the completion of the pruning process. Our data suggest that flow induced changes in tubular architecture ensure proper blood vessel pruning.

  16. Spatial heterogeneity of blood flow in the dog heart. II. Temporal stability in response to adrenergic stimulation.

    Science.gov (United States)

    Deussen, A; Flesche, C W; Lauer, T; Sonntag, M; Schrader, J

    1996-07-01

    The effects of adrenergic stimulation on local myocardial blood flow in the left ventricle were studied in 13 anaesthetized Beagle dogs using the tracer microsphere technique. Adrenergic stimulation was induced by intravenous infusion of orciprenaline (1-2 microg kg-1 min-1) over 15 min or by electrical stimulation of the left ansa subclavia (10 Hz, 1 ms, 4-8 V) over 5 min. Local myocardial blood flow was analysed in 256 samples with an average (+/-SD) mass of 318+/-49 mg from the left ventricular myocardium using a standardized dissection procedure. Orciprenaline increased the average myocardial blood flow from 0.85+/-0.18 to 1.73+/-0.27 ml min-1 g-1, while oxygen consumption and the pressure-rate product increased by 129 and 119% respectively. The coefficients of variation of local myocardial blood flow, a measure of spatial blood flow heterogeneity, were 0.21 and 0.18 under control and orciprenaline respectively. Except for a slight transmural gradient (endomyocardium/epimyocardium flow ratio 1.19) myocardial blood flow did not exhibit significant spatial gradients. Stimulation with orciprenaline increased the average blood flow in all regions of the left ventricle by comparable extents. However, local blood flow during orciprenaline was significantly lower in samples from regions which had a lower blood flow under resting control conditions. A significant positive relationship was obtained between local myocardial blood flow under resting conditions and orciprenaline (r=0.45+/-0.18). Moreover, after recovery from orciprenaline stimulation (i.e. 40-112 min after the end of orciprenaline infusion) local myocardial blood flow exhibited a high degree of correlation with local flow before orciprenaline (r=0.71+/-0.08). Comparable results were obtained with electrical stimulation of the left ansa subclavia. For the comparison stimulation vs. control, the correlation coefficient of local blood flow was 0.52+/-0.04 and for recovery vs. control 0.77+/-0.06. From these

  17. Functional Doppler optical coherence tomography for cortical blood flow imaging

    Science.gov (United States)

    Yu, Lingfeng; Liu, Gangjun; Nguyen, Elaine; Choi, Bernard; Chen, Zhongping

    2010-02-01

    Optical methods have been widely used in basic neuroscience research to study the cerebral blood flow dynamics in order to overcome the low spatial resolution associated with magnetic resonance imaging and positron emission tomography. Although laser Doppler imaging and laser speckle imaging can map out en face cortical hemodynamics and columns, depth resolution is not available. Two-photon microscopy has been used for mapping cortical activity. However, flow measurement requires fluorescent dye injection, which can be problematic. The noninvasive and high resolution tomographic capabilities of optical coherence tomography make it a promising technique for mapping depth resolved cortical blood flow. Here, we present a functional Doppler optical coherence tomography (OCT) imaging modality for quantitative evaluation of cortical blood flow in a mouse model. Fast, repeated, Doppler OCT scans across a vessel of interest were performed to record flow dynamic information with a high temporal resolution of the cardiac cycles. Spectral Doppler analysis of continuous Doppler images demonstrates how the velocity components and longitudinally projected flow-volume-rate change over time, thereby providing complementary temporal flow information to the spatially distributed flow information of Doppler OCT. The proposed functional Doppler OCT imaging modality can be used to diagnose vessel stenosis/blockage or monitor blood flow changes due to pharmacological agents/neuronal activities. Non-invasive in-vivo mice experiments were performed to verify the capabilities of function Doppler OCT.

  18. Active Flow Control

    Science.gov (United States)

    FFOWCS WILLIAMS, J. E.

    2001-01-01

    This paper considers the two-dimensional problem of a plane vortex sheet disturbed by an impulsive line source. A previous incorrect treatment of this problem is examined in detail. Instabilities of the vortex sheet are triggered by the source and grow exponentially in space and time. The Green function is constructed for the problem and it is shown that a point source properly positioned and delayed will induce a field that cancels the unstable growing modes. The resulting displacement of the vortex sheet is expressed in simple terms. The instabilities are checked by the anti-source which combines with the field of the primary source into a vortex sheet response which decays with time at large time. This paper is a contribution to the study of active control of shear layer instabilities, the main contribution being to clear up a previous paper with peculiar results that are, in fact, wrong.

  19. Blood flow and microdialysis in the human femoral head

    DEFF Research Database (Denmark)

    Bøgehøj, Morten; Emmeluth, Claus; Overgaard, Søren

    2007-01-01

    BACKGROUND: If it would be possible to detect lack of flow and/or the development of ischemia in bone, we might have a way of predicting whether a broken bone will heal. We established microdialysis (MD) and laser Doppler (LD) flow measurement in the human femoral head in order to be able to detect...... ischemia and measure changes in blood flow. MATERIAL AND METHODS: In 9 patients undergoing total hip arthroplasty for primary osteoarthrosis, two MD catheters were inserted into the femoral head through two drill holes after the blood flow had been visualized by LD. Then primary samples were collected...... detected within 2 h of cessation of blood flow in most patients....

  20. Establishing the diffuse correlation spectroscopy signal relationship with blood flow.

    Science.gov (United States)

    Boas, David A; Sakadžić, Sava; Selb, Juliette; Farzam, Parisa; Franceschini, Maria Angela; Carp, Stefan A

    2016-07-01

    Diffuse correlation spectroscopy (DCS) measurements of blood flow rely on the sensitivity of the temporal autocorrelation function of diffusively scattered light to red blood cell (RBC) mean square displacement (MSD). For RBCs flowing with convective velocity [Formula: see text], the autocorrelation is expected to decay exponentially with [Formula: see text], where [Formula: see text] is the delay time. RBCs also experience shear-induced diffusion with a diffusion coefficient [Formula: see text] and an MSD of [Formula: see text]. Surprisingly, experimental data primarily reflect diffusive behavior. To provide quantitative estimates of the relative contributions of convective and diffusive movements, we performed Monte Carlo simulations of light scattering through tissue of varying vessel densities. We assumed laminar vessel flow profiles and accounted for shear-induced diffusion effects. In agreement with experimental data, we found that diffusive motion dominates the correlation decay for typical DCS measurement parameters. Furthermore, our model offers a quantitative relationship between the RBC diffusion coefficient and absolute tissue blood flow. We thus offer, for the first time, theoretical support for the empirically accepted ability of the DCS blood flow index ([Formula: see text]) to quantify tissue perfusion. We find [Formula: see text] to be linearly proportional to blood flow, but with a proportionality modulated by the hemoglobin concentration and the average blood vessel diameter.

  1. Stochastic modeling for magnetic resonance quantification of myocardial blood flow

    Science.gov (United States)

    Seethamraju, Ravi T.; Muehling, Olaf; Panse, Prasad M.; Wilke, Norbert M.; Jerosch-Herold, Michael

    2000-10-01

    Quantification of myocardial blood flow is useful for determining the functional severity of coronary artery lesions. With advances in MR imaging it has become possible to assess myocardial perfusion and blood flow in a non-invasive manner by rapid serial imaging following injection of contrast agent. To date most approaches reported in the literature relied mostly on deriving relative indices of myocardial perfusion directly from the measured signal intensity curves. The central volume principle on the other hand states that it is possible to derive absolute myocardial blood flow from the tissue impulse response. Because of the sensitivity involved in deconvolution due to noise in measured data, conventional methods are sub-optimal, hence, we propose to use stochastic time series modeling techniques like ARMA to obtain a robust impulse response estimate. It is shown that these methods when applied for the optical estimation of the transfer function give accurate estimates of myocardial blood flow. The most significant advantage of this approach, compared with compartmental tracer kinetic models, is the use of a minimum set of prior assumptions on data. The bottleneck in assessing myocardial blood flow, does not lie in the MRI acquisition, but rather in the effort or time for post processing. It is anticipated that the very limited requirements for user input and interaction will be of significant advantage for the clinical application of these methods. The proposed methods are validated by comparison with mean blood flow measurements obtained from radio-isotope labeled microspheres.

  2. Radiohalogenated thienylethylamine derivatives for evaluating local cerebral blood flow

    Science.gov (United States)

    Goodman, Mark M.; Knapp, Jr., Furn F.

    1990-01-01

    Radiopharmaceuticals useful in brain imaging comprising radiohalogenated thienylethylamine derivatives. The compounds are 5-halo-thiophene-2-isopropyl amines able to cross the blood-brain barrier and be retained for a sufficient length of time to allow the evaluation or regional blood flow by radioimaging of the brain.

  3. Microvascular blood flow resistance: Role of red blood cell migration and dispersion.

    Science.gov (United States)

    Katanov, Dinar; Gompper, Gerhard; Fedosov, Dmitry A

    2015-05-01

    Microvascular blood flow resistance has a strong impact on cardiovascular function and tissue perfusion. The flow resistance in microcirculation is governed by flow behavior of blood through a complex network of vessels, where the distribution of red blood cells across vessel cross-sections may be significantly distorted at vessel bifurcations and junctions. In this paper, the development of blood flow and its resistance starting from a dispersed configuration of red blood cells is investigated in simulations for different hematocrit levels, flow rates, vessel diameters, and aggregation interactions between red blood cells. Initially dispersed red blood cells migrate toward the vessel center leading to the formation of a cell-free layer near the wall and to a decrease of the flow resistance. The development of cell-free layer appears to be nearly universal when scaled with a characteristic shear rate of the flow. The universality allows an estimation of the length of a vessel required for full flow development, lc ≲ 25D, for vessel diameters in the range 10 μm red blood cell dispersion at vessel bifurcations and junctions on the flow resistance may be significant in vessels which are shorter or comparable to the length lc. Aggregation interactions between red blood cells generally lead to a reduction of blood flow resistance. The simulations are performed using the same viscosity for both external and internal fluids and the RBC membrane viscosity is not considered; however, we discuss how the viscosity contrast may affect the results. Finally, we develop a simple theoretical model which is able to describe the converged cell-free-layer thickness at steady-state flow with respect to flow rate. The model is based on the balance between a lift force on red blood cells due to cell-wall hydrodynamic interactions and shear-induced effective pressure due to cell-cell interactions in flow. We expect that these results can also be used to better understand the flow

  4. Ultrafast Ultrasound Imaging of Ocular Anatomy and Blood Flow

    Science.gov (United States)

    Urs, Raksha; Ketterling, Jeffrey A.; Silverman, Ronald H.

    2016-01-01

    Purpose Ophthalmic ultrasound imaging is currently performed with mechanically scanned single-element probes. These probes have limited capabilities overall and lack the ability to image blood flow. Linear-array systems are able to detect blood flow, but these systems exceed ophthalmic acoustic intensity safety guidelines. Our aim was to implement and evaluate a new linear-array–based technology, compound coherent plane-wave ultrasound, which offers ultrafast imaging and depiction of blood flow at safe acoustic intensity levels. Methods We compared acoustic intensity generated by a 128-element, 18-MHz linear array operated in conventionally focused and plane-wave modes and characterized signal-to-noise ratio (SNR) and lateral resolution. We developed plane-wave B-mode, real-time color-flow, and high-resolution depiction of slow flow in postprocessed data collected continuously at a rate of 20,000 frames/s. We acquired in vivo images of the posterior pole of the eye by compounding plane-wave images acquired over ±10° and produced images depicting orbital and choroidal blood flow. Results With the array operated conventionally, Doppler modes exceeded Food and Drug Administration safety guidelines, but plane-wave modalities were well within guidelines. Plane-wave data allowed generation of high-quality compound B-mode images, with SNR increasing with the number of compounded frames. Real-time color-flow Doppler readily visualized orbital blood flow. Postprocessing of continuously acquired data blocks of 1.6-second duration allowed high-resolution depiction of orbital and choroidal flow over the cardiac cycle. Conclusions Newly developed high-frequency linear arrays in combination with plane-wave techniques present opportunities for the evaluation of ocular anatomy and blood flow, as well as visualization and analysis of other transient phenomena such as vessel wall motion over the cardiac cycle and saccade-induced vitreous motion. PMID:27428169

  5. Effects of nitroglycerin on sublingual microcirculatory blood flow in patients with severe sepsis/septic shock after a strict resuscitation protocol : a double-blind randomized placebo controlled trial

    NARCIS (Netherlands)

    Boerma, E Christiaan; Koopmans, Matty; Konijn, Arjan; Kaiferova, Katerina; Bakker, Andries J; van Roon, Eric N; Buter, Hanneke; Bruins, Nienke; Egbers, Peter H; Gerritsen, Rik T; Koetsier, Peter M; Kingma, W Peter; Kuiper, Michael A; Ince, Can

    2010-01-01

    OBJECTIVES: Microcirculatory alterations have been associated with morbidity and mortality in human sepsis. Such alterations occur despite pressure-guided resuscitation. Earlier data suggested that impaired microcirculatory blood flow could be corrected with intravenous nitroglycerin in these patien

  6. Subcubic Control Flow Analysis Algorithms

    DEFF Research Database (Denmark)

    Midtgaard, Jan; Van Horn, David

    We give the first direct subcubic algorithm for performing control flow analysis of higher-order functional programs. Despite the long held belief that inclusion-based flow analysis could not surpass the ``cubic bottleneck, '' we apply known set compression techniques to obtain an algorithm...... that runs in time O(n^3/log n) on a unit cost random-access memory model machine. Moreover, we refine the initial flow analysis into two more precise analyses incorporating notions of reachability. We give subcubic algorithms for these more precise analyses and relate them to an existing analysis from...

  7. Femoral Blood Flow and Cardiac Output During Blood Flow Restricted Leg Press Exercise

    Science.gov (United States)

    Everett, M. E.; Hackney, K.; Ploutz-Snyder, L.

    2011-01-01

    Low load blood flow restricted resistance exercise (LBFR) causes muscle hypertrophy that may be stimulated by the local ischemic environment created by the cuff pressure. However, local blood flow (BF) during such exercise is not well understood. PURPOSE: To characterize femoral artery BF and cardiac output (CO) during leg press exercise (LP) performed at a high load (HL) and low load (LL) with different levels of cuff pressure. METHODS: Eleven subjects (men/women 4/7, age 31.4+/-12.8 y, weight 68.9+/-13.2 kg, mean+/-SD) performed 3 sets of supine left LP to fatigue with 90 s of rest in 4 conditions: HL (%1-RM/cuff pressure: 80%/0); LL (20%/0); LBFR(sub DBP) (20%/1.3 x diastolic blood pressure, BP); LBFR(sub SBP) (20%/1.3 x supine systolic BP). The cuff remained inflated throughout the LBFR exercise sessions. Artery diameter, velocity time integral (VTI), and stroke volume (SV) were measured using Doppler ultrasound at rest and immediately after each set of exercise. Heart rate (HR) was monitored using a 3-lead ECG. BF was calculated as VTI x vessel cross-sectional area. CO was calculated as HR x SV. The data obtained after each set of exercise were averaged and used for analyses. Multi-level modeling was used to determine the effect of exercise condition on dependent variables. Statistical significance was set a priori at p LL (9.92+/-0.82 cm3) > LBFR(sub dBP)(6.47+/-0.79 cm3) > LBFR(sub SBP) (3.51+/-0.59 cm3). Blunted exercise induced increases occurred in HR, SV, and CO after LBFR compared to HL and LL. HR increased 45% after HL and LL and 28% after LBFR (p<0.05), but SV increased (p<0.05) only after HL. Consequently, the increase (p<0.05) in CO was greater in HL and LL (approximately 3 L/min) than in LBFR (approximately 1 L/min). CONCLUSION: BF during LBFR(sub SBP) was 1/3 of that observed in LL, which supports the hypothesis that local ischemia stimulates the LBFR hypertrophic response. As the cuff did not compress the artery, the ischemia may have occurred

  8. Methods for measurement of cerebral blood flow in man

    DEFF Research Database (Denmark)

    Lassen, N A

    1976-01-01

    A survey of the currently available methods for the measurement of cerebral blood flow in man is given. Many of the clinically important brain diseases such as tumors, stroke, brain trauma or epilepsy entail focal or regional flow alterations. Therefore a special emphasis is placed on methods all...

  9. Blood Flow through an Open-Celled Foam

    Science.gov (United States)

    Ortega, Jason; Maitland, Duncan

    2011-11-01

    The Hazen-Dupuit-Darcy (HDD) equation is commonly used in engineering applications to model the pressure gradient of flow through a porous media. One major advantage of this equation is that it simplifies the complex geometric details of the porous media into two coefficients: the permeability, K, and form factor, C. However through this simplification, the flow details within the porous media are no longer accessible, making it difficult to study the phenomena that contribute to changes in K and C due to clotting of blood flow. To obtain a more detailed understanding of blood flow through a porous media, a direct assessment of the complex interstitial geometry and flow is required. In this study, we solve the Navier-Stokes equations for Newtonian and non-Newtonian blood flow through an open-celled foam geometry obtained from a micro-CT scan. The nominal strut size of the foam sample is of O(10e-5) m and the corresponding Reynolds number based upon this length ranges up to O(10). Fitting the pressure gradient vs. Darcy velocity data with the HDD equation demonstrates that both viscous and inertial forces play an important role in the flow through the foam at these Reynolds numbers. Recirculation zones are observed to form in the wake of the pore struts, producing regions of flow characterized by both low shear rates and long fluid residence times, factors of which have been shown in previous studies to promote blood clotting.

  10. Ultrasonic Imaging of Hemodynamic Force in Carotid Blood Flow

    Science.gov (United States)

    Nitta, N.; Homma, K.

    Hemodynamic forces including blood pressure and shear stress affect vulnerable plaque rupture in arteriosclerosis and biochemical activation of endothelium such as NO production. In this study, a method for estimating and imaging shear stress and pressure gradient distributions in blood vessel as the hemodynamic force based on viscosity estimation is presented. Feasibility of this method was investigated by applying to human carotid blood flow. Estimated results of shear stress and pressure gradient distributions coincide with the ideal distributions obtained by numerical simulation and flow-phantom experiment.

  11. CHARACTERIZATION OF RENAL BLOOD FLOW REGULATION BASED ON WAVELET COEFFICIENTS

    DEFF Research Database (Denmark)

    Pavlov, A.N.; Pavlova, O.N.; Mosekilde, Erik;

    2010-01-01

    The purpose of this study is to demonstrate the possibility of revealing new characteristic features of renal blood flow autoregulation in healthy and pathological states through the application of discrete wavelet transforms to experimental time series for normotensive and hypertensive rats....... A reduction in the variability of the wavelet coefficients in hypertension is observed at both the microscopic level of the blood flow in efferent arterioles of individual nephrons and at the macroscopic level of the blood pressure in the main arteries. The reduction is manifest in both of the main frequency...

  12. Abnormality in cerebellar blood flow in solo vertigo patients

    Energy Technology Data Exchange (ETDEWEB)

    Nagahori, Takeshi [Shakaihoken Takaoka Hospital, Toyama (Japan); Nishijima, Michiharu; Endo, Shunro; Takaku, Akira

    1997-03-01

    Little is known about the blood flow of the vertebrobasilar system as a cause of vertigo and dizziness. We used Xe-CT to study cerebellar blood flow in 53 patients who ranged in age from 35 to 85 years. The patients were divided into two groups. One of them was the vertigo group that comprised 28 patients with rotatory sensation, and the other, the non-vertigo group of 25 patients with a sensation other than rotation. At the stage of severe symptoms, there was decreased cerebellar blood flow in all patients of both, the vertigo and the non-vertigo groups, and a decrease in the bilateral cerebellar hemisphere was observed in five patients and in a unilateral hemisphere in three patients of the vertigo group. By comparison, in the non-vertigo group, unilateral decrease of cerebellar blood flow was observed in only one patient, and a bilateral decrease in five. At the stage of severe symptoms, the mean regional cerebellar blood flow was 40.5{+-}8.0 ml/100 g/min (n=16 sides) in the vertigo group and 45.3{+-}9.5 ml/100 g/min (n=12 sides) in the non-vertigo group. At the stage of moderate symptoms, blood flow image was normal in four of 14 vertigo patients and in seven of 12 non-vertigo patients. The mean regional blood flow was 47.8{+-}8.6 ml/100 g/min (n=28 sides) in the vertigo group and 47.1{+-}5.1 ml/100 g/min (n=24 sides) in the non-vertigo group. At the asymptomatic stage, a high proportion of normal blood flow images (nine of 16 vertigo patients and 10 of 10 non-vertigo patients) was observed. The mean regional cerebellar blood flow was 51.6{+-}10.7 ml/100 g/min (n=32 sides) in the vertigo group and 52.8{+-}8.5 ml/100 g/min (n=20 sides) in the non-vertigo group. This study demonstrates that a unilateral or bilateral decrease in blood flow of the vertebrobasilar system may cause vertigo and dizziness. It also shows that Xe-CT of the cerebellum may be a valuable examination modality for the diagnosis and treatment of vertigo and dizziness. (author)

  13. Vasoactive enzymes and blood flow responses to passive and active exercise in peripheral arterial disease

    DEFF Research Database (Denmark)

    Walker, Meegan A.; Høier, Birgitte; Walker, Philip J.;

    2016-01-01

    Background: Peripheral arterial disease (PAD) is characterised by impaired leg blood flow, which contributes to claudication and reduced exercise capacity. This study investigated to what extent vasoactive enzymes might contribute to altered blood flow in PAD (Fontaine stage II). Methods: We...... compared femoral artery blood flow during reactive hyperaemia, leg-extension exercise and passive leg movement, and determined the level of vasoactive enzymes in skeletal muscle samples from the vastus lateralis in PAD (n = 10, 68.5 ± 6.5 years) and healthy controls (CON, n = 9, 62.1 ± 12.3 years). Leg...... than CON (1.04 ± 0.19 vs 0.50 ± 0.06 AU, P = 0.02), with no differences for other enzymes. Leg blood flow during exercise was correlated with prostacyclin synthase (P = 0.001). Conclusion: Elevated NADPH oxidase indicates that oxidative stress may be a primary cause of low nitric oxide availability...

  14. Viscoelastic capillary flow: the case of whole blood

    Directory of Open Access Journals (Sweden)

    David Rabaud

    2016-07-01

    Full Text Available The dynamics of spontaneous capillary flow of Newtonian fluids is well-known and can be predicted by the Lucas-Washburn-Rideal (LWR law. However a wide variety of viscoelastic fluids such as alginate, xanthan and blood, does not exhibit the same Newtonian behavior.In this work we consider the Herschel-Bulkley (HB rheological model and Navier-Stokes equation to derive a generic expression that predicts the capillary flow of non-Newtonian fluids. The Herschel-Bulkley rheological model encompasses a wide variety of fluids, including the Power-law fluids (also called Ostwald fluids, the Bingham fluids and the Newtonian fluids. It will be shown that the proposed equation reduces to the Lucas-Washburn-Rideal law for Newtonian fluids and to the Weissenberg-Rabinowitsch-Mooney (WRM law for power-law fluids. Although HB model cannot reduce to Casson’s law, which is often used to model whole blood rheology, HB model can fit the whole blood rheology with the same accuracy.Our generalized expression for the capillary flow of non-Newtonian fluid was used to accurately fit capillary flow of whole blood. The capillary filling of a cylindrical microchannel by whole blood was monitored. The blood first exhibited a Newtonian behavior, then after 7 cm low shear stress and rouleaux formation made LWR fails to fit the data: the blood could not be considered as Newtonian anymore. This non-Newtonian behavior was successfully fit by the proposed equation.

  15. Coded ultrasound for blood flow estimation using subband processing

    DEFF Research Database (Denmark)

    Gran, Fredrik; Udesen, Jesper; Nielsen, Michael bachmann

    2007-01-01

    This paper further investigates the use of coded excitation for blood flow estimation in medical ultrasound. Traditional autocorrelation estimators use narrow-band excitation signals to provide sufficient signal-to-noise-ratio (SNR) and velocity estimation performance. In this paper, broadband...... was carried out using an experimental ultrasound scanner and a commercial linear array 7 MHz transducer. A circulating flow rig was scanned with a beam-to-flow angle of 60 degrees. The flow in the rig was laminar and had a parabolic flow-profile with a peak velocity of 0.09 m/s. The mean relative standard...

  16. Tubuloglomerular feedback dynamics and renal blood flow autoregulation in rats

    DEFF Research Database (Denmark)

    Holstein-Rathlou, N H; Wagner, A J; Marsh, D J

    1991-01-01

    To decide whether tubuloglomerular feedback (TGF) can account for renal autoregulation, we tested predictions of a TGF simulation. Broad-band and single-frequency perturbations were applied to arterial pressure; arterial blood pressure, renal blood flow and proximal tubule pressure were measured....... Data were analyzed by linear systems analysis. Broad-band forcings of arterial pressure were also applied to the model to compare experimental results with simulations. With arterial pressure as the input and tubular pressure, renal blood flow, or renal vascular resistance as outputs, the model......Hz in which, in addition, there are autonomous oscillations in TGF. Higher amplitude forcings in this band were attenuated by autoregulatory mechanisms, but low-amplitude forcings entrained the autonomous oscillations and provoked amplified oscillations in blood flow, showing an effect of TGF on whole kidney...

  17. Cerebral blood flow and oxygen metabolism in the Rett syndrome

    Energy Technology Data Exchange (ETDEWEB)

    Yoshikawa, Hideto; Fueki, Noboru; Suzuki, Hisaharu; Sakuragawa, Norio; Iio, Masaaki (National Central Hospital for Mental, Nervous and Muscular Disorders, Tokyo (Japan))

    1992-05-01

    Positron emission tomography (PET) was performed on six patients with the Rett syndrome and the results were compared with the concurrent clinical status of the patients. The cerebral metabolic rate of oxygen (CMRO{sub 2}) was low in five patients, and oxygen extraction fraction (OEF) was low in four patients; both had a tendency to decline with advancing age. Although the cause is unknown, it is suggested that impaired oxidative metabolism exists in the Rett syndrome. An analysis of the distribution among brain regions showed that the ratios of values for the frontal cortex to those for the temporal cortex for both the cerebral blood flow (CBF) and CMRO{sub 2} were lower than those for the controls, which may indicate the loss of of hyperfrontality in the Rett syndrome. Distribution of brain metabolism may be immature in the Rett syndrome. (author).

  18. Peculiarities of Brain's Blood Flow : Role of Carbon Dioxide

    CERN Document Server

    Gersten, Alexander

    2011-01-01

    Among the major factors controlling the cerebral blood flow (CBF), the effect of PaCO2 is peculiar in that it violates autoregulatory CBF mechanisms and allows to explore the full range of the CBF. This research resulted in a simple physical model, with a four parameter formula, relating the CBF to PaCO2. The parameters can be extracted in an easy manner, directly from the experimental data. With this model earlier experimental data sets of Rhesus monkeys and rats were well fitted. Human data were also fitted with this model. Exact formulae were found, which can be used to transform the fits of one animal to the fits of another one. The merit of this transformation is that it enable us the use of rats data as monkeys data simply by rescaling the PaCO2 values and the CBF data. This transformation makes possible the use of experimental animal data instead of human ones.

  19. Quantifying Blood Flow in the DIEP Flap: An Ultrasonographic Study

    Directory of Open Access Journals (Sweden)

    Joseph Richard Dusseldorp, BCom, MBBS(Hons

    2014-10-01

    Conclusions: This study confirms that perforator size is a critical factor in optimizing blood flow in perforator-based free tissue transfer. Further research is required to understand the flow dynamics of perforator flaps based on multiple perforators. However, surgeons should be cognizant that a single large perforator may have substantially higher flow rates than multiple small perforators. Routine FVI calculation is recommended to ensure complete flap survival.

  20. Pulsatile blood flow, shear force, energy dissipation and Murray's Law

    Directory of Open Access Journals (Sweden)

    Bengtsson Hans-Uno

    2006-08-01

    Full Text Available Abstract Background Murray's Law states that, when a parent blood vessel branches into daughter vessels, the cube of the radius of the parent vessel is equal to the sum of the cubes of the radii of daughter blood vessels. Murray derived this law by defining a cost function that is the sum of the energy cost of the blood in a vessel and the energy cost of pumping blood through the vessel. The cost is minimized when vessel radii are consistent with Murray's Law. This law has also been derived from the hypothesis that the shear force of moving blood on the inner walls of vessels is constant throughout the vascular system. However, this derivation, like Murray's earlier derivation, is based on the assumption of constant blood flow. Methods To determine the implications of the constant shear force hypothesis and to extend Murray's energy cost minimization to the pulsatile arterial system, a model of pulsatile flow in an elastic tube is analyzed. A new and exact solution for flow velocity, blood flow rate and shear force is derived. Results For medium and small arteries with pulsatile flow, Murray's energy minimization leads to Murray's Law. Furthermore, the hypothesis that the maximum shear force during the cycle of pulsatile flow is constant throughout the arterial system implies that Murray's Law is approximately true. The approximation is good for all but the largest vessels (aorta and its major branches of the arterial system. Conclusion A cellular mechanism that senses shear force at the inner wall of a blood vessel and triggers remodeling that increases the circumference of the wall when a shear force threshold is exceeded would result in the observed scaling of vessel radii described by Murray's Law.

  1. Luteal blood flow in patients undergoing GnRH agonist long protocol

    Directory of Open Access Journals (Sweden)

    Takasaki Akihisa

    2011-01-01

    Full Text Available Abstract Background Blood flow in the corpus luteum (CL is closely related to luteal function. It is unclear how luteal blood flow is regulated. Standardized ovarian-stimulation protocol with a gonadotropin-releasing hormone agonist (GnRHa long protocol causes luteal phase defect because it drastically suppresses serum LH levels. Examining luteal blood flow in the patient undergoing GnRHa long protocol may be useful to know whether luteal blood flow is regulated by LH. Methods Twenty-four infertile women undergoing GnRHa long protocol were divided into 3 groups dependent on luteal supports; 9 women were given ethinylestradiol plus norgestrel (Planovar orally throughout the luteal phase (control group; 8 women were given HCG 2,000 IU on days 2 and 4 day after ovulation induction in addition to Planovar (HCG group; 7 women were given vitamin E (600 mg/day orally throughout the luteal phase in addition to Planovar (vitamin E group. Blood flow impedance was measured in each CL during the mid-luteal phase by transvaginal color-pulsed-Doppler-ultrasonography and was expressed as a CL-resistance index (CL-RI. Results Serum LH levels were remarkably suppressed in all the groups. CL-RI in the control group was more than the cutoff value (0.51, and only 2 out of 9 women had CL-RI values Conclusion Patients undergoing GnRHa long protocol had high luteal blood flow impedance with very low serum LH levels. HCG administration improved luteal blood flow impedance. This suggests that luteal blood flow is regulated by LH.

  2. Cerebral blood flow tomography with xenon-133

    DEFF Research Database (Denmark)

    Lassen, N A

    1985-01-01

    and investigative purposes. This article discusses in particular its use for the selection of patients with carotid occlusion for extracranial/intracranial bypass surgery, for detection of severe arterial spasm after aneurysm bleeding, and for detection of low flow areas during severe migraine attacks. The use...

  3. Noninvasive measurement of human blood glucose under flow control of time gate%血流控制下时间门的人体血糖无创实验测量

    Institute of Scientific and Technical Information of China (English)

    袁渊; 孙美秀; 姜琛昱; 龚智勇; 杨基春

    2014-01-01

    Objective In order to further improve the noninvasive measurement precision of human blood glucose and achieve clinical requirements,experiments were conducted to measure human blood glucose by a novel measurement method our group proposed.Methods The blood flow of the tested parts was stopped by pressure,and dynamic distribution of transmission spectra was measured by time-correlated single-photon counting (TCSPC) technology under the dual wavelength light incident.Oral glucose tolerance test (OGTT) was conducted on three human subjects,and the early arriving photons were selected by Laplace transform.Meanwhile,the human blood glucose concentration was measured using the Roche glucose meter.Results The best curve fitting was got when the Laplace parameter was 1Gs-1 (determining parameter R2=0.0922).Conclusions The experimental results showed that better measurement accuracy can be obtained by selecting appropriate Laplace parameter,and noninvasive measurement of human blood glucose under flow control of time gate was feasible.%目的 为了进一步提高人体血糖无创伤测量的精度,从而达到临床的要求,对本课题组提出的人体血糖无创伤测量的新方法进行实验测量.方法 在利用压力停止受测部分血流条件下,采用时间相关单光子计数技术测量双波长光入射下透射光谱的动态分布.对3例人体进行了口服葡萄糖耐量试验(OGTT),用拉普拉斯变换选取早期到达的光子,同时用罗氏血糖仪对人体血糖浓度进行读数.结果 当拉普拉斯参数取1Gs-1时,实验测得的参数斜率(PS)随人体血糖浓度变化曲线的拟合度最好(决定系数R2=0.0922).结论 实验测量结果显示,选取合适的拉普拉斯参数可以得到更好的测量准确性,基于血流控制下的时间门技术用于无创伤测量人体血糖浓度是可行的.

  4. Impact of extracorporeal blood flow rate on blood pressure, pulse rate and cardiac output during haemodialysis

    DEFF Research Database (Denmark)

    Schytz, Philip Andreas; Mace, Maria Lerche; Soja, Anne Merete Boas

    2015-01-01

    BACKGROUND: If blood pressure (BP) falls during haemodialysis (HD) [intradialytic hypotension (IDH)] a common clinical practice is to reduce the extracorporeal blood flow rate (EBFR). Consequently the efficacy of the HD (Kt/V) is reduced. However, only very limited knowledge on the effect of redu...

  5. Nocturnal variations in peripheral blood flow, systemic blood pressure, and heart rate in humans

    DEFF Research Database (Denmark)

    Sindrup, J H; Kastrup, J; Christensen, H;

    1991-01-01

    Subcutaneous adipose tissue blood flow rate, together with systemic arterial blood pressure and heart rate under ambulatory conditions, was measured in the lower legs of 15 normal human subjects for 12-20 h. The 133Xe-washout technique, portable CdTe(Cl) detectors, and a portable data storage unit...

  6. Design and Simulation of Axial Flow Maglev Blood Pump

    Directory of Open Access Journals (Sweden)

    Huachun Wu

    2011-03-01

    Full Text Available The axial flow maglev blood pump (AFMBP has become a global research focus and emphasis for artificial ventricular assist device, which has no mechanical contact, mechanical friction, compact structure and light weight, can effectively solve thrombus and hemolysis. Magnetic suspension and impeller is two of the important parts in the axial flow maglev blood pump, and their structure largely determines the blood pump performance. The research adopts electromagnetic and fluid finite element analysis, and puts forward a method to design the magnetic suspension and impeller of axial flow blood pump, which tacks into account the small volume of axial blood pump. The magnetic bearing’s characteristics are evaluated by electromagnetic finite element analysis. The Blades have been designed by calculating aerofoil bone line, and make simulation analysis for different thicken ways of blade by Fluent software, and make a conclusion that the blade thickened with certain rules has better characteristics in the same conditions. The results will provide some guidance for design of axial flow maglev blood pump, and establish theoretical basis for application of the implantable artificial heart pump.

  7. Complex blood flow quantification using real-time in vivo vector flow ultrasound

    DEFF Research Database (Denmark)

    Pedersen, Mads Møller; Pihl, Michael Johannes; Per, Haugaard;

    A new method to define and quantify complex blood flow is presented. The standard deviations of real-time in vivo vector flow angle estimates are used. Using vector flow ultrasound imaging both carotid bifurcations of two healthy volunteers were scanned. Scanning was performed with a 7.6 MHz linear...... patterns can be visualised and quantified with real-time in vivo vector flow. Good agreement between visual evaluation and the quantitative method has been shown. A standard deviation of vector angle estimates above 30 is proposed to define complex blood flow....

  8. [The landmarks of the measurement of cerebral blood flow].

    Science.gov (United States)

    István, Nyáry

    2008-01-30

    History of the measurement of local cerebral blood flow may cover a period of one and a half centuries. Parallel forthcoming of both theoretical and technical development were the key elements of ensuing progress resulting in the present state, when by the aid of in vivo blood flow and metabolic maps, we can visualize locales of brain functioning and their interconnections. Two theoretical landmarks should be mentioned in this historic process. First, the work of Adolf Fick, as the starter of quantitative measurements in this field, and Seymour Kety's model of a single, homogenously perfused tissue element. The solution of this model, in the form of Kety's equation is still fundamental to present day blood flow mapping techniques. Among the numerous investigators over the past years, two Hungarian scientist can be named as major contributors. Kálmán Sántha made substantial studies with continuous registration of local cerebral blood flow by the aid of thermocouples, while Emil P6sztor invented the hydrogen clearance method for the measurement of local cerebral blood flow both in human and in animal studies.

  9. Regional neurohypophysial and hypothalamic blood flow in rats during hypercapnia

    Energy Technology Data Exchange (ETDEWEB)

    Bryan, R.M. Jr.; Myers, C.L.; Page, R.B.

    1988-08-01

    Regional cerebral blood flow (rCBF) was measured in the neurohypophysis and hypothalamus in normocapnic and hypercapnic rats using (/sup 14/C)isopropyliodoamphetamine. Rats were surgically prepared using nitrous oxide and halothane and placed in plaster restraining casts. Hypercapnia was produced by increasing the fractional concentration of inspired CO/sub 2/ (FICO/sub 2/). rCBF in normocapnic rats was higher in the paraventricular nucleus, supraoptic nucleus, median eminence, and neural lobe than rates previously measured by use of diffusible tracers. During hypercapnia blood flow increased linearly with arterial PCO/sub 2/ (PACO/sub 2/) in all regions except the median eminence and neural lobe, which were not affected by hypercapnia. When rats were pretreated with phentolamine (1 mg/kg) to block the alpha-adrenergic receptors, blood flow in the median eminence and neural lobe increased significantly during hypercapnia. We conclude that blood flow in the cell bodies of the paraventricular nucleus and supraoptic nucleus is regulated differently during hypercapnia than blood flow in the nerve terminals in the median eminence and neural lobe. Furthermore, vasodilation produced by increased CO/sub 2/ is offset by alpha-receptor stimulation in the median eminence and neural lobe.

  10. An analysis of the sluicing gate in pulmonary blood flow.

    Science.gov (United States)

    Fung, Y C; Zhuang, F Y

    1986-05-01

    For pulmonary blood flow in zone 2 condition, in which the blood pressure in the venule (pven) is lower than the alveolar gas pressure (pA), the blood exiting from the capillary sheet and entering a venule must go through a sluicing gate. The sluicing gate exists because the venule remains patent while the capillaries will collapse when the static pressure of blood falls below the alveolar gas pressure. In the original theory of sheet flow the effect of the tension in the interalveolar septa on the flow through the sluicing gate was ignored. Since the tension multiplied by the curvature of the membrane is equivalent to a lateral pressure tending to open the gate, and since the curvature of the capillary wall is high in the gate region, this effect may be important. The present analysis improves the original theory and demonstrates that the effect of membrane tension is to cause flow to increase when the venous pressure continues to decrease. The shape of the sluicing gate resembles that of a venturi tube, and can be determined by an iterative integration of the differential equations. The result forms an important link in the theory of pulmonary blood flow in zone 2 condition.

  11. Effects of Aortic Irregularities on the Blood Flow

    Science.gov (United States)

    Gutmark-Little, Iris; Prahl-Wittberg, Lisa; van Wyk, Stevin; Mihaescu, Mihai; Fuchs, Laszlo; Backeljauw, Philippe; Gutmark, Ephraim

    2013-11-01

    Cardiovascular defects characterized by geometrical anomalies of the aorta and its effect on the blood flow are investigated. The flow characteristics change with the aorta geometry and the rheological properties of the blood. Flow characteristics such as wall shear stress often play an important role in the development of vascular disease. In the present study, blood is considered to be non-Newtonian and is modeled using the Quemada model, an empirical model that is valid for different red blood cell loading. Three patient-specific aortic geometries are studied using Large Eddy Simulations (LES). The three geometries represent malformations that are typical in patients populations having a genetic disorder called Turner syndrome. The results show a highly complex flow with regions of recirculation that are enhanced in two of the three aortas. Moreover, blood flow is diverted, due to the malformations, from the descending aorta to the three side branches of the arch. The geometry having an elongated transverse aorta has larger areas of strong oscillatory wall shear stress.

  12. Profound spatial heterogeneity of coronary reserve. Discordance between patterns of resting and maximal myocardial blood flow.

    Science.gov (United States)

    Austin, R E; Aldea, G S; Coggins, D L; Flynn, A E; Hoffman, J I

    1990-08-01

    We examined the ability of individual regions of the canine left ventricle to increase blood flow relative to baseline rates of perfusion. Regional coronary flow was measured by injecting radioactive microspheres over 90 seconds in seven anesthetized mongrel dogs. Preliminary experiments demonstrated a correlation between the regional distributions of blood flow during asphyxia and pharmacological vasodilatation with adenosine (mean r = 0.75; 192 regions in each of two dogs), both of which resulted in increased coronary flow. Subsequent experiments, during which coronary perfusion pressure was held constant at 80 mm Hg, examined the pattern of blood flow in 384 regions (mean weight, 106 mg) of the left ventricular free wall during resting flow and during maximal coronary flow effected by intracoronary adenosine infusion. We found that resting and maximal flow patterns were completely uncorrelated to each other in a given dog (mean r = 0.06, p = NS; n = 3 dogs). Furthermore, regional coronary reserve, defined as the ratio of maximal to resting flow, ranged from 1.75 (i.e., resting flow was 57% of maximum) to 21.9 (resting flow was 4.5% of maximum). Thus, coronary reserve is spatially heterogeneous and determined by two distinct perfusion patterns: the resting (control) pattern and the maximal perfusion pattern. Normal hearts, therefore, contain small regions that may be relatively more vulnerable to ischemia. This may explain the patchy nature of infarction with hypoxia and at reduced perfusion pressures as well as the difficulty of using global parameters to predict regional ischemia. Despite the wide dispersion of coronary reserve, we found, by autocorrelation analysis, that reserve in neighboring regions (even when separated by a distance of several tissue samples) was significantly correlated. This also applied to patterns of resting myocardial flow. Thus, both resting coronary blood flow and reserve appear to be locally continuous and may define functional

  13. Coded Ultrasound for Blood Flow Estimation Using Subband Processing

    DEFF Research Database (Denmark)

    Gran, Fredrik; Udesen, Jesper; Nielsen, Michael Bachamnn

    2008-01-01

    This paper investigates the use of coded excitation for blood flow estimation in medical ultrasound. Traditional autocorrelation estimators use narrow-band excitation signals to provide sufficient signal-to-noise-ratio (SNR) and velocity estimation performance. In this paper, broadband coded...... for velocity estimation is compared with a conventional approach transmitting a narrow-band pulse. The study was carried out using an experimental ultrasound scanner and a commercial linear array 7 MHz transducer. A circulating flow rig was scanned with a beam-to-flow angle of 60°. The flow in the rig...

  14. Doppler Assessment of Uterine Blood Flow in Recurrent Pregnancy Loss

    Directory of Open Access Journals (Sweden)

    Maryam Barzin

    2011-05-01

    Full Text Available Recurrent spontaneous abortion affects 2%-5% of"ncouples. Uterine perfusion is considered as one of the"nfactors that influences the success of implantation."nDuring the normal menstrual cycle, the impedance"nto uterine artery blood flow diminishes progressively"nduring the luteal phase, reaching the lowest values"nin the period coinciding with the implantation time."nImpedance of uterine arteries is a good indicator of"nthe possibility of a subsequent pregnancy. High blood"nflow resistance is associated with a reduced conception"nrate and women with lower pulsatility index values"nhave the highest possibility of becoming pregnant. An"nimpaired uterine perfusion could play a major role in"nthe pathogenesis of recurrent spontaneous abortion. In"nthis study, we examined sixty women with recurrent"nspontaneous abortion and a control group including"nthirty normal women with at least one previous"nuncomplicated pregnancy and without history of any"nabortion. Transvaginal sonography associated with"nDoppler flow measurement was performed during"nthe midluteal phase of a cycle in all women. The"nmeasurement of the ascending branch of both right"nand left uterine arteries was taken lateral to the cervix"nat the level of the internal os. The pulsatility and"nresistance index of both uterine arteries were calculated"nand compared in both groups. In this presentation we"nreport our finding in two groups. We also explain the"nexact method of study and present some interesting"ncases

  15. Spinal Cord Blood Flow after Ischemic Preconditioning in a Rat Model of Spinal Cord Ischemia

    Directory of Open Access Journals (Sweden)

    David Zvara

    2004-01-01

    Full Text Available Spinal cord blood flow after ischemic preconditioning is poorly characterized. This study is designed to evaluate spinal cord blood flow patterns in animals after acute ischemic preconditioning. Experiment 1: After a laminectomy and placement of a laser Doppler probe over the lumbar spinal cord to measure spinal cord blood flow, 16 male Sprague-Dawley rats were randomized into two groups: ischemic preconditioning (IPC, n = 8, and control (CTRL, n = 8. Rats in the CTRL and the IPC groups were subjected to 12 min of ischemia directly followed by 60 min of reperfusion. IPC rats received 3 min of IPC and 30 min of reperfusion prior to the 12-min insult period. Experiment 2: After instrumentation, the rats were randomized into three groups: control (CTRL, n = 7, ischemic preconditioning (IPC, n = 7, and time control (TC, n = 4. Rats in the CTRL and the IPC groups were subjected to the same ischemia and reperfusion protocol as above. The TC group was anesthetized for the same time period as the CTRL and the IPC groups, but had no ischemic intervention. Microspheres were injected at baseline and at 15 and 60 min into the final reperfusion. All rats were euthanized and tissue harvested for spinal cord blood flow analysis. In Experiment 1, there was a slight, significant difference in spinal cord blood flow during the ischemic period; however, this difference soon disappeared during reperfusion. In experiment 2, there was no difference in blood flow at any experimental time. The results of these experiments demonstrate that IPC slightly enhances blood flow to the spinal cord during ischemia; however, this effect is not sustained during the reperfusion period.

  16. Maximum Likelihood Blood Velocity Estimator Incorporating Properties of Flow Physics

    DEFF Research Database (Denmark)

    Schlaikjer, Malene; Jensen, Jørgen Arendt

    2004-01-01

    The aspect of correlation among the blood velocities in time and space has not received much attention in previous blood velocity estimators. The theory of fluid mechanics predicts this property of the blood flow. Additionally, most estimators based on a cross-correlation analysis are limited...... of simulated and in vivo data from the carotid artery. The estimator is meant for two-dimensional (2-D) color flow imaging. The resulting mathematical relation for the estimator consists of two terms. The first term performs a cross-correlation analysis on the signal segment in the radio frequency (RF......)-data under investigation. The flow physic properties are exploited in the second term, as the range of velocity values investigated in the cross-correlation analysis are compared to the velocity estimates in the temporal and spatial neighborhood of the signal segment under investigation. The new estimator...

  17. Mediators of increased blood flow in porcine skin

    Directory of Open Access Journals (Sweden)

    H. D. Moore

    1992-01-01

    Full Text Available Nicotinates and benzalkonium chloride (B.Cl cause inflammatory changes in human skin, thought to be dependent upon prostaglandin formation. This study has examined the effects of hexyl-nicotinate (HN and B.Cl on blood flow in porcine skin. The role of prostaglandins and interleukin (IL-1 in the blood flow response has been investigated. Blood flow was increased by both HN and B.Cl, the response to B.Cl being more protracted. Cyclooxygenase inhibitor pretreatment reduced these responses. IL-1-like biological activity was identified in normal porcine epidermis and the amounts recovered from inflamed skin were similar. Thus prostaglandin formation in HN or B.Cl-induced inflammation, if IL-1 dependent, is not associated with the loss of significant amounts of the cytokine from the epidermis.

  18. Reduced blood flow to contracting skeletal muscle in ageing humans

    DEFF Research Database (Denmark)

    Nyberg, Michael Permin; Hellsten, Ylva

    2016-01-01

    The ability to sustain a given absolute submaximal workload declines with advancing age likely due to a lower level of blood flow and O2 delivery to the exercising muscles. Given that physical inactivity mimics many of the physiological changes associated with ageing, separating the physiological...... consequences of ageing and physical inactivity can be challenging; yet, observations from cross-sectional and longitudinal studies on the effects of physical activity have provided some insight. Physical activity has the potential to offset the age-related decline in blood flow to contracting skeletal muscle...... the O2 demand of the active skeletal muscle of aged individuals during conditions where systemic blood flow is not limited by cardiac output seems to a large extent to be related to the level of physical activity. This article is protected by copyright. All rights reserved....

  19. Regulation of the skeletal muscle blood flow in humans

    DEFF Research Database (Denmark)

    Mortensen, Stefan; Saltin, Bengt

    2014-01-01

    In humans, skeletal muscle blood flow is regulated by an interaction between several locally formed vasodilators including nitric oxide (NO) and prostaglandins. In plasma, ATP is a potent vasodilator that stimulates the formation of NO and prostaglandins and very importantly can offset local...... concentration does not increase during exercise. In the skeletal muscle interstitium, there is a marked increase in the concentration of ATP and adenosine and this increase is tightly coupled to the increase in blood flow. The sources of interstitial ATP and adenosine are thought to be skeletal muscle cells...... hyperaemia whereas the role of ATP remains uncertain due to lack of specific purinergic receptor blockers for human use. The purpose of this review is to address the interaction between vasodilator systems and to discuss the multiple proposed roles of ATP in human skeletal muscle blood flow regulation...

  20. Coronary blood flow during cardiopulmonary resuscitation in swine

    Energy Technology Data Exchange (ETDEWEB)

    Bellamy, R.F.; DeGuzman, L.R.; Pedersen, D.C.

    1984-01-01

    Recent papers have raised doubt as to the magnitude of coronary blood flow during closed-chest cardiopulmonary resuscitation. We will describe experiments that concern the methods of coronary flow measurement during cardiopulmonary resuscitation. Nine anesthetized swine were instrumented to allow simultaneous measurements of coronary blood flow by both electromagnetic cuff flow probes and by the radiomicrosphere technique. Cardiac arrest was caused by electrical fibrillation and closed-chest massage was performed by a Thumper (Dixie Medical Inc., Houston). The chest was compressed transversely at a rate of 66 strokes/min. Compression occupied one-half of the massage cycle. Three different Thumper piston strokes were studied: 1.5, 2, and 2.5 inches. Mean aortic pressure and total systemic blood flow measured by the radiomicrosphere technique increased as Thumper piston stroke was lengthened (mean +/- SD): 1.5 inch stroke, 23 +/- 4 mm Hg, 525 +/- 195 ml/min; 2 inch stroke, 33 +/- 5 mm Hg, 692 +/- 202 ml/min; 2.5 inch stroke, 40 +/- 6 mm Hg, 817 +/- 321 ml/min. Both methods of coronary flow measurement (electromagnetic (EMF) and radiomicrosphere (RMS)) gave similar results in technically successful preparations (data expressed as percent prearrest flow mean +/- 1 SD): 1.5 inch stroke, EMF 12 +/- 5%, RMS 16 +/- 5%; 2 inch stroke, EMF 30 +/- 6%, RMS 26 +/- 11%; 2.5 inch stroke, EMF 50 +/- 12%, RMS 40 +/- 20%. The phasic coronary flow signal during closed-chest compression indicated that all perfusion occurred during the relaxation phase of the massage cycle. We concluded that coronary blood flow is demonstrable during closed-chest massage, but that the magnitude is unlikely to be more than a fraction of normal.

  1. Flow of Red Blood Cells in Stenosed Microvessels

    Science.gov (United States)

    Vahidkhah, Koohyar; Balogh, Peter; Bagchi, Prosenjit

    2016-06-01

    A computational study is presented on the flow of deformable red blood cells in stenosed microvessels. It is observed that the Fahraeus-Lindqvist effect is significantly enhanced due to the presence of a stenosis. The apparent viscosity of blood is observed to increase by several folds when compared to non-stenosed vessels. An asymmetric distribution of the red blood cells, caused by geometric focusing in stenosed vessels, is observed to play a major role in the enhancement. The asymmetry in cell distribution also results in an asymmetry in average velocity and wall shear stress along the length of the stenosis. The discrete motion of the cells causes large time-dependent fluctuations in flow properties. The root-mean-square of flow rate fluctuations could be an order of magnitude higher than that in non-stenosed vessels. Several folds increase in Eulerian velocity fluctuation is also observed in the vicinity of the stenosis. Surprisingly, a transient flow reversal is observed upstream a stenosis but not downstream. The asymmetry and fluctuations in flow quantities and the flow reversal would not occur in absence of the cells. It is concluded that the flow physics and its physiological consequences are significantly different in micro- versus macrovascular stenosis.

  2. Intraoperative multi-exposure speckle imaging of cerebral blood flow.

    Science.gov (United States)

    Richards, Lisa M; Kazmi, Sm Shams; Olin, Katherine E; Waldron, James S; Fox, Douglas J; Dunn, Andrew K

    2017-01-01

    Multiple studies have demonstrated that laser speckle contrast imaging (LSCI) has high potential to be a valuable cerebral blood flow monitoring technique during neurosurgery. However, the quantitative accuracy and sensitivity of LSCI is limited, and highly dependent on the exposure time. An extension to LSCI called multi-exposure speckle imaging (MESI) overcomes these limitations, and was evaluated intraoperatively in patients undergoing brain tumor resection. This clinical study ( n = 8) recorded multiple exposure times from the same cortical tissue area spanning 0.5-20 ms, and evaluated images individually as single-exposure LSCI and jointly using the MESI model. This study demonstrated that the MESI estimates provided the broadest flow sensitivity for sampling the flow magnitude in the human brain, closely followed by the shorter exposure times. Conservation of flow analysis on vascular bifurcations was used to validate physiological accuracy, with highly conserved flow estimates (blood flow changes after tissue cautery. Results from this study demonstrate that intraoperative MESI can be performed with high quantitative accuracy and sensitivity for cerebral blood flow monitoring.

  3. Diabetes augments in vivo microvascular blood flow dynamics after stroke.

    Science.gov (United States)

    Tennant, Kelly A; Brown, Craig E

    2013-12-04

    Stroke usually affects people with underlying medical conditions. In particular, diabetics are significantly more likely to have a stroke and the prognosis for recovery is poor. Because diabetes is associated with degenerative changes in the vasculature of many organs, we sought to determine how hyperglycemia affects blood flow dynamics after an ischemic stroke. Longitudinal in vivo two-photon imaging was used to track microvessels before and after photothrombotic stroke in a diabetic mouse model. Chronic hyperglycemia exacerbated acute (3-7 d) ischemia-induced increases in blood flow velocity, vessel lumen diameter, and red blood cell flux in peri-infarct regions. These changes in blood flow dynamics were most evident in superficial blood vessels within 500 μm from the infarct, rather than deeper or more distant cortical regions. Long-term imaging of diabetic mice not subjected to stroke indicated that these acute stroke-related changes in vascular function could not be attributed to complications from hyperglycemia alone. Treating diabetic mice with insulin immediately after stroke resulted in less severe alterations in blood flow within the first 7 d of recovery, but had more variable results at later time points. Analysis of microvessel branching patterns revealed that stroke led to a pruning of microvessels in peri-infarct cortex, with very few instances of sprouting. These results indicate that chronic hyperglycemia significantly affects the vascular response to ischemic stroke and that insulin only partially mitigates these changes. The combination of these acute and chronic alterations in blood flow dynamics could underlie diabetes-related deficits in cortical plasticity and stroke recovery.

  4. Blood flow in transplantable bladder tumors treated with hematoporphyrin derivative and light

    Energy Technology Data Exchange (ETDEWEB)

    Selman, S.H.; Kreimer-Birnbaum, M.; Klaunig, J.E.; Goldblatt, P.J.; Keck, R.W.; Britton, S.L.

    1984-05-01

    Following hematoporphyrin derivative (HPD) photochemotherapy, blood flow to transplantable N-(4-(5-nitro-2-furyl)-2-thia-zolyl) formamide-induced urothelial tumors was determined by a radioactive microsphere technique using either /sup 103/Ru or /sup 141/Ce. Two tumors were implanted s.c. on the abdominal wall of Fischer 344 weanling rats. HPD (10 mg/kg body weight) was administered 24 hr prior to phototherapy (red light, greater than 590 nm; 360 J/sq cm). One of the two tumors was shielded from light exposure and served as an internal control. Blood flows were determined in control animals that received no treatment (Group 1), HPD only (Group 2), or light only (Group 3). In Groups 4 and 5, animals received the combination of HPD and light but differed in the time interval between treatment and blood flow determinations (10 min and 24 hr, respectively). Only blood flow to tumors treated with HPD and light showed a significant decrease (p less than 0.05) when compared with their internal controls both at 10 min (Group 4) and 24 hr (Group 5) after completion of phototherapy. These studies suggest that disruption of tumor blood flow may be an important mechanism of action of this method of cancer therapy.

  5. Fontan Outcomes and Pulmonary Blood Flow at Birth.

    Science.gov (United States)

    Evans, William N; Acherman, Ruben J; Reardon, Leigh C; Ciccolo, Michael L; Galindo, Alvaro; Rothman, Abraham; Winn, Brody J; Yumiaco, Noel S; Restrepo, Humberto

    2016-01-01

    We previously noted, in a small group of post-Fontan patients, a possible association between hepatic fibrosis scores and the status of pulmonary blood flow at birth. To further explore this observation, we examined data from all Fontan patients seen in our center from July 2010 to March 2015. We identified 200 patients for analysis. Of the 200 patients, 56 underwent transvenous-hepatic biopsy. Of the 200 patients, 13 (6.5%) had protein-losing enteropathy. We divided both the 56 biopsy patients and the entire cohort of 200 patients into 4 groups: (1) unobstructed pulmonary blood flow at birth with functional left ventricles, (2) unobstructed pulmonary blood flow at birth with functional right ventricles, (3) obstructed pulmonary blood flow at birth with functional left ventricles, and (4) obstructed pulmonary blood flow at birth with functional right ventricles. Analysis of the 56 liver-biopsy patient groups showed median hepatic total-fibrosis scores for the 4 groups of 2 (0-6), 2 (0-8), 3 (2-6), and 4 (1-8), respectively, with statistical significance between groups 4 and 1 (p = 0.031). For the entire cohort of 200 patients, we analyzed the incidence of protein-losing enteropathy for each of the four groups and found protein-losing enteropathy percent occurrences of 0, 2.9, 8.8, and 16.1, respectively, with statistical significance between groups 4 and 2 (p = 0.031) and between groups 4 and 1 (p = 0.025). A history of obstructed pulmonary blood flow at birth, coupled with a functional right ventricle, may predict a poorer long-term Fontan outcome.

  6. Adrenergic influence on gastric mucosal blood flow in gastric fistula dogs

    DEFF Research Database (Denmark)

    Hovendal, C P; Bech, K; Gottrup, F;

    1984-01-01

    by an initial increase in mucosal blood flow and in the last two periods a decrease in blood flow. alpha-Blockade (phentolamine) reduced the pentagastrin stimulated gastric acid secretion and gastric mucosal blood flow but the ratio between blood flow and acid secretion was increased, indicating a relatively...

  7. Multiverse data-flow control.

    Science.gov (United States)

    Schindler, Benjamin; Waser, Jürgen; Ribičić, Hrvoje; Fuchs, Raphael; Peikert, Ronald

    2013-06-01

    In this paper, we present a data-flow system which supports comparative analysis of time-dependent data and interactive simulation steering. The system creates data on-the-fly to allow for the exploration of different parameters and the investigation of multiple scenarios. Existing data-flow architectures provide no generic approach to handle modules that perform complex temporal processing such as particle tracing or statistical analysis over time. Moreover, there is no solution to create and manage module data, which is associated with alternative scenarios. Our solution is based on generic data-flow algorithms to automate this process, enabling elaborate data-flow procedures, such as simulation, temporal integration or data aggregation over many time steps in many worlds. To hide the complexity from the user, we extend the World Lines interaction techniques to control the novel data-flow architecture. The concept of multiple, special-purpose cursors is introduced to let users intuitively navigate through time and alternative scenarios. Users specify only what they want to see, the decision which data are required is handled automatically. The concepts are explained by taking the example of the simulation and analysis of material transport in levee-breach scenarios. To strengthen the general applicability, we demonstrate the investigation of vortices in an offline-simulated dam-break data set.

  8. Spring-network-based model of a red blood cell for simulating mesoscopic blood flow.

    Science.gov (United States)

    Nakamura, Masanori; Bessho, Sadao; Wada, Shigeo

    2013-01-01

    We developed a mechanical model of a red blood cell (RBC) that is capable of expressing its characteristic behaviors in shear flows. The RBC was modeled as a closed shell membrane consisting of spring networks in the framework of the energy minimum concept. The fluid forces acting on RBCs were modeled from Newton's viscosity law and the conservation of momentum. In a steady shear flow, the RBC model exhibited various behaviors, depending on the shear rate; it tumbled, tank-treaded, or both. The transition from tumbling to tank-treading occurred at a shear rate of 20 s( - 1). The simulation of an RBC in steady and unsteady parallel shear flows (Couette flows) showed that the deformation parameters of the RBC were consistent with experimental results. The RBC in Poiseuille flow migrated radially towards the central axis of the flow channel. Axial migration became faster with an increase in the viscosity of the media, qualitatively consistent with experimental results. These results demonstrate that the proposed model satisfies the essential conditions for simulating RBC behavior in blood flow. Finally, a large-scale RBC flow simulation was implemented to show the capability of the proposed model for analyzing the mesoscopic nature of blood flow.

  9. Splanchnic blood flow and hepatic glucose production in exercising humans

    DEFF Research Database (Denmark)

    Bergeron, R; Kjaer, M; Simonsen, L;

    2001-01-01

    The study examined the implication of the renin-angiotensin system (RAS) in regulation of splanchnic blood flow and glucose production in exercising humans. Subjects cycled for 40 min at 50% maximal O(2) consumption (VO(2 max)) followed by 30 min at 70% VO(2 max) either with [angiotensin-converti......The study examined the implication of the renin-angiotensin system (RAS) in regulation of splanchnic blood flow and glucose production in exercising humans. Subjects cycled for 40 min at 50% maximal O(2) consumption (VO(2 max)) followed by 30 min at 70% VO(2 max) either with [angiotensin...

  10. High speed optical holography of retinal blood flow

    CERN Document Server

    Pellizzari, Mathilde; Degardin, Julie; Sahel, Jose-Alain; Fink, Mathias; Paques, Michel; Atlan, Michael

    2016-01-01

    We performed non-invasive video imaging of retinal blood flow in a pigmented rat by holographic interferometry of near-infrared laser light backscattered by retinal tissue, beating against an off-axis reference beam sampled at a frame rate of 39 kHz with a high throughput camera. Local Doppler contrasts emerged from the envelopes of short-time Fourier transforms and the phase of autocorrelation functions of holograms rendered by Fresnel transformation. This approach permitted imaging of blood flow in large retinal vessels (30 microns diameter) over 400 by 400 pixels with a spatial resolution of 8 microns and a temporal resolution of 6.5 ms.

  11. Age and gender related differences in aortic blood flow

    DEFF Research Database (Denmark)

    Traberg, Marie Sand; Pedersen, Mads Møller; Hemmsen, Martin Christian

    2012-01-01

    The abdominal aorta (AA) is predisposed to development of abdominal aneurysms (AAA), a focal dilatation of the artery with fatal consequences if left untreated. The blood flow patterns in the AA is thought to play an important role in the development of AAA. The purpose of this work is to investi......The abdominal aorta (AA) is predisposed to development of abdominal aneurysms (AAA), a focal dilatation of the artery with fatal consequences if left untreated. The blood flow patterns in the AA is thought to play an important role in the development of AAA. The purpose of this work...

  12. Cerebral blood flow and oxidative metabolism during human endotoxemia

    DEFF Research Database (Denmark)

    Møller, Kirsten; Strauss, Gitte Irene; Qvist, Jesper;

    2002-01-01

    The proinflammatory cytokine, tumor necrosis factor-alpha (TNF-alpha), has been suggested to mediate septic encephalopathy through an effect on cerebral blood flow (CBF) and metabolism. The effect of an intravenous bolus of endotoxin on global CBF, metabolism, and net flux of cytokines...... and catecholamines was investigated in eight healthy young volunteers. Cerebral blood flow was measured by the Kety-Schmidt technique at baseline (during normocapnia and voluntary hyperventilation for calculation of subject-specific cerebrovascular CO reactivity), and 90 minutes after an intravenous bolus...

  13. A New Technology for Detecting Cerebral Blood Flow

    DEFF Research Database (Denmark)

    Schytz, Henrik W; Guo, Song; Jensen, Lars T;

    2012-01-01

    There is a need for real-time non-invasive, continuous monitoring of cerebral blood flow (CBF) during surgery, in intensive care units and clinical research. We investigated a new non-invasive hybrid technology employing ultrasound tagged near infrared spectroscopy (UT-NIRS) that may estimate...... changes in CBF using a cerebral blood flow index (CFI). Changes over time for UT-NIRS CFI and (133)Xenon single photon emission computer tomography ((133)Xe-SPECT) CBF data were assessed in 10 healthy volunteers after an intravenous bolus of acetazolamide. UT-NIRS CFI was measured continuously and SPECT...

  14. Accurate blood flow measurements: are artificial tracers necessary?

    Directory of Open Access Journals (Sweden)

    Christian Poelma

    Full Text Available Imaging-based blood flow measurement techniques, such as particle image velocimetry, have become an important tool in cardiovascular research. They provide quantitative information about blood flow, which benefits applications ranging from developmental biology to tumor perfusion studies. Studies using these methods can be classified based on whether they use artificial tracers or red blood cells to visualize the fluid motion. We here present the first direct comparison in vivo of both methods. For high magnification cases, the experiments using red blood cells strongly underestimate the flow (up to 50% in the present case, as compared to the tracer results. For medium magnification cases, the results from both methods are indistinguishable as they give the same underestimation of the real velocities (approximately 33%, based on in vitro reference measurements. These results suggest that flow characteristics reported in literature cannot be compared without a careful evaluation of the imaging characteristics. A method to predict the expected flow averaging behavior for a particular facility is presented.

  15. Accurate blood flow measurements: are artificial tracers necessary?

    Science.gov (United States)

    Poelma, Christian; Kloosterman, Astrid; Hierck, Beerend P; Westerweel, Jerry

    2012-01-01

    Imaging-based blood flow measurement techniques, such as particle image velocimetry, have become an important tool in cardiovascular research. They provide quantitative information about blood flow, which benefits applications ranging from developmental biology to tumor perfusion studies. Studies using these methods can be classified based on whether they use artificial tracers or red blood cells to visualize the fluid motion. We here present the first direct comparison in vivo of both methods. For high magnification cases, the experiments using red blood cells strongly underestimate the flow (up to 50% in the present case), as compared to the tracer results. For medium magnification cases, the results from both methods are indistinguishable as they give the same underestimation of the real velocities (approximately 33%, based on in vitro reference measurements). These results suggest that flow characteristics reported in literature cannot be compared without a careful evaluation of the imaging characteristics. A method to predict the expected flow averaging behavior for a particular facility is presented.

  16. Regional cerebral blood flow in focal cortical epilepsy

    DEFF Research Database (Denmark)

    Hougaard, Kristina Dupont; Oikawa, T; Sveinsdottir, E;

    1976-01-01

    Regional cerebral blood flow (rCBF) was studied in ten patients with focal cortical epilepsy. The blood flow was measured by the intra-arterial injection of xenon 133 (133Xe), and the isotope clearance was recorded by a multidetector scintillation camera with 254 detectors. Three patients were...... studied both during a seizure and (in the same setting) in the interictal period; six patients were studied only in the interictal period, and one patient was studied only during a seizure. Studies during seizures all showed marked flow increases in areas presumed to participate in the seizure activity....... This finding accords with earlier studies. All nine patients studied in the interictal phase showed, either spontaneously or during activation by intermittent light, focal flow increases in areas presumed to comprise the epileptic focus. These interictal hyperemic foci probably reflect subictal neuronal...

  17. Improved technique for blood flow velocity measurement using Doppler effect

    Science.gov (United States)

    Valadares Oliveira, Eduardo J.; Nantes Button, Vera L. d. S.; Maia, Joaquim M.; Costa, Eduardo T.

    2002-04-01

    The Doppler velocimeter developed allows to determine the angle between the ultrasonic beam and the velocity vector of the flow, and to calculate the precise blood flow in a vessel. Four piezoelectric transducers constitute the Doppler velocimeter. Three of these transducers are positioned to form an equilateral triangle (base of a pyramid). When these transducers move simultaneously, backward or forward from the initial position, the emitted ultrasonic beams focalize on a position (peak of the pyramid) closer or farther from the transducers faces, according to the depth of the vessel where we intend to measure de flow. The angle between the transducers allows adjusting the height of this pyramid and the position of the focus (where the three beams meet). A forth transducer is used to determine the diameter of the vessel and monitor the position of the Doppler velocimeter relative to the vessel. Simulation results showed that with this technique is possible to accomplish precise measurement of blood flow.

  18. Renal cortical and medullary blood flow responses to altered NO availability in humans

    DEFF Research Database (Denmark)

    Damkjær, Mads; Vafaee, Manoucher; Møller, Michael L;

    2010-01-01

    , tissue layers with a thickness of one voxel were eliminated stepwise from the external surface of the VOI (voxel peeling), and the blood flow subsequently was determined in each new, reduced VOI. Blood flow in the shrinking VOIs decreased as the number of cycles of voxel peeling increased. After 4......-5 cycles, blood flow was not reduced further by additional voxel peeling. This volume-insensitive flow was measured to be 2.30 ± 0.17 ml·g tissue(-1)·min(-1) during the control period; it increased during infusion of glyceryl nitrate to 2.97 ± 0.18 ml·g tissue(-1)·min(-1) (P

  19. Laser speckle contrast imaging for monitoring changes in microvascular blood flow

    DEFF Research Database (Denmark)

    Ambrus, Rikard; Strandby, Rune B.; Svendsen, Lars Bo;

    2016-01-01

    BACKGROUND/AIMS: Microvascular blood flow is essential for healing and predicts surgical outcome. The aim of the current study was to investigate the relation between fluxes measured with the laser speckle contrast imaging (LSCI) technique and changes in absolute blood flow. In addition, we studied...... the reproducibility of the LSCI technique when assessing the intra-abdominal microcirculation of the pig. METHODS: During trial 1, a fish gill arch was mechanically perfused with heparinized fish blood under controlled stepwise-altered flow rates alongside mechanically induced movement artefacts. The microcirculation...... = 6.0, 3.2, and 6.4%, respectively). CONCLUSION: Due to the non-contact and real-time assessment over large areas, LSCI is a promising technique for the intraoperative assessment of intra-abdominal microcirculation. A linear correlation between flux and volumetric flow was found, in accordance...

  20. Planning-free cerebral blood flow territory mapping in patients with intracranial arterial stenosis.

    Science.gov (United States)

    Arteaga, Daniel F; Strother, Megan K; Davis, L Taylor; Fusco, Matthew R; Faraco, Carlos C; Roach, Brent A; Scott, Allison O; Donahue, Manus J

    2016-07-07

    A noninvasive method for quantifying cerebral blood flow and simultaneously visualizing cerebral blood flow territories is vessel-encoded pseudocontinuous arterial spin labeling MRI. However, obstacles to acquiring such information include limited access to the methodology in clinical centers and limited work on how clinically acquired vessel-encoded pseudocontinuous arterial spin labeling data correlate with gold-standard methods. The purpose of this work is to develop and validate a semiautomated pipeline for the online quantification of cerebral blood flow maps and cerebral blood flow territories from planning-free vessel-encoded pseudocontinuous arterial spin labeling MRI with gold-standard digital subtraction angiography. Healthy controls (n = 10) and intracranial atherosclerotic disease patients (n = 34) underwent 3.0 T MRI imaging including vascular (MR angiography) and hemodynamic (cerebral blood flow-weighted arterial spin labeling) MRI. Patients additionally underwent catheter and/or CT angiography. Variations in cross-territorial filling were grouped according to diameters of circle of Willis vessels in controls. In patients, Cohen's k-statistics were computed to quantify agreement in perfusion patterns between vessel-encoded pseudocontinuous arterial spin labeling and angiography. Cross-territorial filling patterns were consistent with circle of Willis anatomy. The intraobserver Cohen's k-statistics for cerebral blood flow territory and digital subtraction angiography perfusion agreement were 0.730 (95% CI = 0.593-0.867; reader one) and 0.708 (95% CI = 0.561-0.855; reader two). These results support the feasibility of a semiautomated pipeline for evaluating major neurovascular cerebral blood flow territories in patients with intracranial atherosclerotic disease.

  1. Thermogenic response to adrenaline during restricted blood flow in the forearm

    DEFF Research Database (Denmark)

    Simonsen, L; Stefl, B; Christensen, N J

    1999-01-01

    To elucidate the underlying mechanism behind the thermogenic effect of adrenaline in human skeletal muscle, nine healthy subjects were studied during intravenous infusion of adrenaline. Restriction of blood flow to one forearm was obtained by external compression of the brachial artery, to separate...... a direct metabolic effect of adrenaline from an effect dependent on increased blood flow. The other arm served as the control arm. In the control arm, the forearm blood flow increased 4.7-fold (from 2.0 +/- 0.3 to 9.3 +/- 1.5 mL 100 g(-1) min(-1), P adrenaline infusion. Adrenaline...... not increase (baseline period: 5.6 +/- 2.3 micromol 100 g(-1) min(-1), adrenaline period: 6.1 +/- 2.1 micromol 100 g(-1) min(-1), P = 0.54). The experimental design and the difficulties in interpretation of the result are discussed. The results give evidence for the hypothesis that the vascular system plays...

  2. Single photon emission CT perfusion imaging of cerebral blood flow of early syphilis patients

    Institute of Scientific and Technical Information of China (English)

    施辛; 吴锦昌; 刘增礼; 唐军; 苏玉华

    2003-01-01

    Objective To injvestigate the cerebral blood flow of patients with early syphilis. Methods 99Tcm-ECD as brain perfusion imaging agent was used in single photon emission computed tomography (SPECT) for 32 patients with early syphilis and 15 controls. Visual analyses were made on every BSPECT image. Results The 32 patients with early syphilis had general, patchy hypoperfusion of cerebral blood flow. Fourteen of the 32 patients had 48 episodes of marked patchy hypoperfusion of rCBF. The responsible areas of hypoperfusion in a patchy distribution involved the left frontal lobe (6 episodes), right frontal lobe (3), left parietal lobe (7), right parietal lobe (6), left temporal lobe (11), right temporal lobe (5), left occipital lobe (3), left basal ganglia (3), cerebellum (1), and nerve nuceus (1). No abnormality was found in the control group.Conclusions Cerebral blood flow abnormalities exist in patients with early syphilis. General patchy hypoperfusion on SPECT imaging is common.

  3. Role of nitric oxide in maintenance of basal oral tissue blood flow in anesthetized cats.

    Science.gov (United States)

    Koss, M C; Yu, Y

    2000-09-01

    Experiments were undertaken to determine if nitric oxide (NO) plays a role in regulation of basal blood flow in the oral cavity of pentobarbital anesthetized cats and, if so, to quantify this effect using dose-response relationships. Blood flow was continuously measured from the surface of the tongue and mandibular gingiva (laser-Doppler flowmetry) and from the lingual artery (ultrasonic flowmetry). Cardiovascular parameters also were recorded. Administration of the nonselective inhibitor of nitric oxide synthase (NOS), L-NAME (0.08-20 mg/kg i.v.), produced a dose-related increase of blood pressure associated with decreases of blood flow at all three measurement sites. Maximal blood flow depression of 50-60% was seen 30-60 min after administration of 1.25 mg/kg of L-NAME. D-NAME (1.25 mg/kg i.v.) was inactive at all sites. Subsequent administration of L-arginine partially reversed effects of L-NAME in the lingual artery and tongue, but not in the gingival circulation. The neuronally selective NOS inhibitor, 7-nitroindazole (7-NI, 30 mg/kg i.p.), was devoid of effect on any of the measured parameters. These results suggest that endothelial (but not neuronally derived) NO plays an important role in control of basal blood flow in oral tissues of the cat.

  4. Age and gender related differences in aortic blood flow

    Science.gov (United States)

    Enevoldsen, Marie Sand; Pedersen, Mads Møller; Hemmsen, Martin Christian; Lönn, Lars; Henneberg, Kaj-Åge; Jensen, Jørgen Arendt

    2012-03-01

    The abdominal aorta (AA) is predisposed to development of abdominal aneurysms (AAA), a focal dilatation with fatal consequences if left untreated. The blood flow patterns is thought to play an important role in the development of AAA. The purpose of this work is to investigate the blood flow patterns within a group of healthy volunteers (six females, eight males) aged 23 to 76 years to identify changes and differences related to age and gender. The healthy volunteers were categorized by gender (male/female) and age (below/above 35 years). Subject-specific flow and geometry data were acquired using the research interface on a Profocus ultrasound scanner (B-K Medical, Herlev, Denmark; segmentation of 3D magnetic resonance angiography (Magnetom Trio, Siemens Healthcare, Erlangen, Germany). The largest average diameter was among the elderly males (19.7 (+/- 1.33) mm) and smallest among the young females (12.4 (+/- 0.605) mm). The highest peak systolic velocity was in the young female group (1.02 (+/- 0.336) m/s) and lowest in the elderly male group (0.836 (+/- 0.127) m/s). A geometrical change with age was observed as the AA becomes more bended with age. This also affects the blood flow velocity patterns, which are markedly different from young to elderly. Thus, changes in blood flow patterns in the AA related to age and gender are observed. Further investigations are needed to determine the relation between changes in blood flow patterns and AAA development.

  5. Laser Doppler flowmetry is valid for measurement of cerebral blood flow autoregulation lower limit in rats

    DEFF Research Database (Denmark)

    Tonnesen, Jan; Pryds, Anders; Larsen, Erik Hviid

    2005-01-01

    Laser Doppler flowmetry (LDF) is a recent technique that is increasingly being used to monitor relative changes in cerebral blood flow whereas the intra-arterial 133xenon injection technique is a well-established method for repeated absolute measurements of cerebral blood flow. The aim of this st...... CO2 challenge. Haemodilution influences the two methods differently causing relative overestimation of blood flow by the laser Doppler technique compared to the 133xenon method....... of this study was to validate LDF for assessment of cerebral autoregulation and CO2 reactivity with the 133xenon injection technique as the gold standard. Simultaneous measurements of cerebral blood flow (CBF) were collected by LDF (CBFLDF) and the 133xenon method (CBFXe) while (1) cerebral autoregulation...... was challenged by controlled systemic haemorrhage, or (2) cerebral blood flow was varied by manipulating the arterial partial pressure of CO2 (Pa,CO2). LDF slightly overestimated CBF under conditions of haemorrhagic shock and haemodilution caused by controlled haemorrhage (paired t test, P

  6. Regional cerebral blood flow during hypoxia-ischemia in immature rats

    Energy Technology Data Exchange (ETDEWEB)

    Vannucci, R.C.; Lyons, D.T.; Vasta, F.

    1988-02-01

    Immature rats subjected to a combination of unilateral common carotid artery ligation and hypoxia sustain brain damage confined largely to the ipsilateral cerebral hemisphere. To ascertain the extent and distribution of ischemic alterations in the brains of these small animals, we modified the Sakurada technique to measure regional cerebral blood flow using carbon-14 autoradiography. Seven-day-old rats underwent right common carotid artery ligation following which they were rendered hypoxic with 8% O2 at 37 degrees C. Before and during hypoxia, the rat pups received an injection of iodo(/sup 14/C)antipyrine for determination of regional cerebral blood flow. Blood flows to individual structures of the ipsilateral cerebral hemisphere were not influenced by arterial occlusion alone; flows to the contralateral hemisphere and to the brainstem and cerebellum actually increased by 25-50%. Hypoxia-ischemia was associated with decreases in regional cerebral blood flow of the ipsilateral hemisphere such that by 2 hours, flows to subcortical white matter, neocortex, striatum, and thalamus were 15, 17, 34, and 41% of control, respectively. The hierarchy of the blood flow reductions correlated closely with the distribution and extent of ischemic neuronal necrosis. However, unlike the pathologic pattern of this model, the degree of ischemia appeared homogeneous within each brain region. Blood flows to contralateral cerebral hemispheric structures were relatively unchanged from prehypoxic values, whereas flows to the brainstem and cerebellum nearly doubled and tripled, respectively. Thus, ischemia is the predominant factor that determines the topography of tissue injury to major regions of immature rat brain, whereas metabolic factors may influence the heterogeneous pattern of damage seen within individual structures.

  7. [Measurement of cerebral blood flow by thermal diffusion using a flow probe with a Peltier stack].

    Science.gov (United States)

    Yamagata, S; Kikuchi, H; Hashimoto, K; Minamikawa, J; Watanabe, Y

    1987-05-01

    In order to evaluate the blood flow by means of thermal diffusion, relationship between blood flow and parameters induced by thermal diffusion was investigated. Flow probe employed for measurement by thermal diffusion incorporated a Peltier stack which contained a small semiconductor and two L-shaped gold plates. These two plates were attached to both sides of the semiconductor by one side of each gold plate and the other side was surfaced with a tissue to be measured. Temperature gradient is created with current applied to the Peltier stack between two plates, one cooled and the other heated, and it is affected only by tissue blood flow. Two kinds of parameters of thermal diffusion were subjected to compare to blood flow. One was temperature gradient when the constant current was applied to the Peltier stack. The other was a current required to maintain a definite temperature gradient which was determined before hand. From the theoretical principle in thermodynamics, the correlations between blood flow and each of thermal diffusion parameters were defined by the following equations: (Formula: see text) where F is blood flow, delta V is voltage converted from temperature gradient, and Ci and Cv are constants. Each of phi v and phi i indicates the characteristics of each probe. Experimental study was carried out to confirm the above relationship using cortex of experimental animals. Under the general anesthesia, a cat was placed in prone position. After the craniotomy, dura mater was opened and a small flow probe, 10 mm in diameter, 5 mm in height and 5 g in weight, was placed on the cortex and blood flow was continuously evaluated by two parameters.(ABSTRACT TRUNCATED AT 250 WORDS)

  8. Ultrasonic Doppler blood flow meter for extracorporeal circulation

    Science.gov (United States)

    Dantas, Ricardo G.; Costa, Eduardo T.; Maia, Joaquim M.; Nantes Button, Vera L. d. S.

    2000-04-01

    In cardiac surgeries it is frequently necessary to carry out interventions in internal heart structures, and where the blood circulation and oxygenation are made by artificial ways, out of the patient's body, in a procedure known as extracorporeal circulation (EC). During this procedure, one of the most important parameters, and that demands constant monitoring, is the blood flow. In this work, an ultrasonic pulsed Doppler blood flowmeter, to be used in an extracorporeal circulation system, was developed. It was used a 2 MHz ultrasonic transducer, measuring flows from 0 to 5 liters/min, coupled externally to the EC arterial line destined to adults perfusion (diameter of 9.53 mm). The experimental results using the developed flowmeter indicated a maximum deviation of 3.5% of full scale, while the blood flow estimator based in the rotation speed of the peristaltic pump presented deviations greater than 20% of full scale. This ultrasonic flowmeter supplies the results in a continuous and trustworthy way, and it does not present the limitations found in those flowmeters based in other transduction methods. Moreover, due to the fact of not being in contact with the blood, it is not disposable and it does not need sterilization, reducing operational costs and facilitating its use.

  9. Dietary fiber and blood pressure control.

    Science.gov (United States)

    Aleixandre, A; Miguel, M

    2016-04-01

    In the past few years, new strategies to control blood pressure levels are emerging by developing new bioactive components of foods. Fiber has been linked to the prevention of a number of cardiovascular diseases and disorders. β-Glucan, the main soluble fiber component in oat grains, was initially linked to a reduction in plasma cholesterol. Several studies have shown afterward that dietary fiber may also improve glycaemia, insulin resistance and weight loss. The effect of dietary fiber on arterial blood pressure has been the subject of far fewer studies than its effect on the above-mentioned variables, but research has already shown that fiber intake can decrease arterial blood pressure in hypertensive rats. Moreover, certain fibers can improve arterial blood pressure when administered to hypertensive and pre-hypertensive subjects. The present review summarizes all those studies which attempt to establish the antihypertensive effects of dietary fiber, as well as its effect on other cardiovascular risk factors.

  10. Skin blood flow and local temperature independently modify sweat rate during passive heat stress in humans.

    Science.gov (United States)

    Wingo, Jonathan E; Low, David A; Keller, David M; Brothers, R Matthew; Shibasaki, Manabu; Crandall, Craig G

    2010-11-01

    Sweat rate (SR) is reduced in locally cooled skin, which may result from decreased temperature and/or parallel reductions in skin blood flow. The purpose of this study was to test the hypotheses that decreased skin blood flow and decreased local temperature each independently attenuate sweating. In protocols I and II, eight subjects rested supine while wearing a water-perfused suit for the control of whole body skin and internal temperatures. While 34°C water perfused the suit, four microdialysis membranes were placed in posterior forearm skin not covered by the suit to manipulate skin blood flow using vasoactive agents. Each site was instrumented for control of local temperature and measurement of local SR (capacitance hygrometry) and skin blood flow (laser-Doppler flowmetry). In protocol I, two sites received norepinephrine to reduce skin blood flow, while two sites received Ringer solution (control). All sites were maintained at 34°C. In protocol II, all sites received 28 mM sodium nitroprusside to equalize skin blood flow between sites before local cooling to 20°C (2 sites) or maintenance at 34°C (2 sites). In both protocols, individuals were then passively heated to increase core temperature ~1°C. Both decreased skin blood flow and decreased local temperature attenuated the slope of the SR to mean body temperature relationship (2.0 ± 1.2 vs. 1.0 ± 0.7 mg·cm(-2)·min(-1)·°C(-1) for the effect of decreased skin blood flow, P = 0.01; 1.2 ± 0.9 vs. 0.07 ± 0.05 mg·cm(-2)·min(-1)·°C(-1) for the effect of decreased local temperature, P = 0.02). Furthermore, local cooling delayed the onset of sweating (mean body temperature of 37.5 ± 0.4 vs. 37.6 ± 0.4°C, P = 0.03). These data demonstrate that local cooling attenuates sweating by independent effects of decreased skin blood flow and decreased local skin temperature.

  11. Development of a miniature intraventricular axial flow blood pump.

    Science.gov (United States)

    Yamazaki, K; Umezu, M; Koyanagi, H; Outa, E; Ogino, S; Otake, Y; Shiozaki, H; Fujimoto, T; Tagusari, O; Kitamura, M

    1993-01-01

    A new intraventricular axial flow blood pump has been designed and developed as a totally implantable left ventricular assist device (LVAD). This pump consists of an impeller combined with a guide-vane, a tube housing, and a DC motor. The pump is introduced into the LV cavity through the LV apex, and the outlet cannula is passed antegrade across the aortic valve. Blood is withdrawn from the LV through the inlet ports at the pump base, and discharged to the ascending aorta. Our newly developed axial flow pump system has the following advantages: 1) it is a simple and compact system, 2) minimal blood stasis both in the device and the LV cavity, 3) minimal blood contacting surface of the pump, 4) easy accessibility with a less invasive surgical procedure, and 5) low cost. A pump flow > 5 L/min was obtained against 100 mmHg differential pressure in the mock circulatory system. The pump could produce a passive pulsatile flow effect with a beating heart more efficiently than other non-pulsatile pumps because of minimal pressure drop and inertia along the bypass tract. Anatomic fit studies using dissected hearts of dilated cardiomyopathy (DCM) cadavers showed that this pump could smoothly pass through the aortic valve without any interference with mitral valve function. Recently, a dynamic pressure groove bearing and a miniature lip seal have been developed. The dynamic pressure groove bearing has a simple structure and acts as a pressure resistant sealing mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

  12. Longitudinal Cerebral Blood Flow Changes during Speech in Hereditary Ataxia

    Science.gov (United States)

    Sidtis, John J.; Strother, Stephen C.; Naoum, Ansam; Rottenberg, David A.; Gomez, Christopher

    2010-01-01

    The hereditary ataxias constitute a group of degenerative diseases that progress over years or decades. With principal pathology involving the cerebellum, dysarthria is an early feature of many of the ataxias. Positron emission tomography was used to study regional cerebral blood flow changes during speech production over a 21 month period in a…

  13. Nocturnal foot blood flow in patients with arterial insufficiency

    DEFF Research Database (Denmark)

    Jelnes, Rolf; Tønnesen, K H

    1984-01-01

    was on average the same in patients with normal circulations and in patients with different degrees of arterial insufficiency (mean: 2.0 +/- 0.8 ml min-1 100 g-1). During sleep the blood flow nearly doubled in patients with normal circulations; no systematic change was seen in patients with intermittent...

  14. [Measurement of cerebral blood flow using phase-contrast MRI].

    Science.gov (United States)

    Obata, T; Shishido, F; Koga, M; Ikehira, H; Kimura, F; Yoshida, K

    1997-07-01

    The development of phase-contrast magnetic resonance imaging(P-C MRI) provides a noninvasive method for measurement of volumetric blood flow(VFR). The VFR of the left and right internal carotid arteries and basilar artery were measured using P-C MRI, and total cerebral blood flow(tCBF) was calculated by summing up the VFR values in three vessels. We investigated the changes in these blood flows as influenced from age, head size, height, weight, body surface area and handedness. Moreover, regional CBF(rCBF) was measured by combining with the single photon emission computed tomography(SPECT) of 123I. The blood flows were 142 +/- 58 mL/ min(mean +/- SD) in the basilar artery, 229 +/- 86 mL/min in the left, 223 +/- 58 mL/min in the right internal carotid artery, and tCBF was 617 +/- 128 mL/min(Ref. Magn Resn Imaging 14:P. 1143, 1996). Significant increases were observed in head-size-related change of VFR in the basilar artery and height-related change of tCBF. The value of rCBF was easily acquired in combination with SPECT. Phase-contrast MRI is useful for a noninvasive and rapid analysis of cerebral VFR and has potential for clinical use.

  15. Patterns of regional cerebral blood flow in acute stroke

    DEFF Research Database (Denmark)

    Olsen, T S; Skriver, E B

    1981-01-01

    In a consecutive group of 56 stroke patients the regional cerebral blood flow was measured within 84 hours after stroke. A 254 multidetector scintillation camera and the intracarotid Xenon-133 injection method was used to study rCBF. Typical rCBF-patterns are described and compared to the findings...

  16. Vasodilator interactions in skeletal muscle blood flow regulation

    DEFF Research Database (Denmark)

    Hellsten, Ylva; Nyberg, Michael Permin; Jensen, Lasse Gliemann;

    2012-01-01

    that this remaining hyperemia may be explained by cAMP and cGMP independent smooth muscle relaxation, such as effects of endothelial derived hyperpolarization factors (EDHFs) or through metabolic modulation of sympathetic effects. The nature and role of EDHF as well as potential novel mechanisms in muscle blood flow...

  17. A VARIATIONAL MODEL FOR 2-D MICROPOLAR BLOOD FLOW

    Institute of Scientific and Technical Information of China (English)

    He Ji-huan

    2003-01-01

    The micropolar fluid model is an essential generalization of the well-established Navier-Stokes model in the sense that it takes into account the microstructure of the fluid.This paper is devolted to establishing a variational principle for 2-D incompressible micropolar blood flow.

  18. Optically measured microvascular blood flow contrast of malignant breast tumors.

    Directory of Open Access Journals (Sweden)

    Regine Choe

    Full Text Available Microvascular blood flow contrast is an important hemodynamic and metabolic parameter with potential to enhance in vivo breast cancer detection and therapy monitoring. Here we report on non-invasive line-scan measurements of malignant breast tumors with a hand-held optical probe in the remission geometry. The probe employs diffuse correlation spectroscopy (DCS, a near-infrared optical method that quantifies deep tissue microvascular blood flow. Tumor-to-normal perfusion ratios are derived from thirty-two human subjects. Mean (95% confidence interval tumor-to-normal ratio using surrounding normal tissue was 2.25 (1.92-2.63; tumor-to-normal ratio using normal tissues at the corresponding tumor location in the contralateral breast was 2.27 (1.94-2.66, and using normal tissue in the contralateral breast was 2.27 (1.90-2.70. Thus, the mean tumor-to-normal ratios were significantly different from unity irrespective of the normal tissue chosen, implying that tumors have significantly higher blood flow than normal tissues. Therefore, the study demonstrates existence of breast cancer contrast in blood flow measured by DCS. The new, optically accessible cancer contrast holds potential for cancer detection and therapy monitoring applications, and it is likely to be especially useful when combined with diffuse optical spectroscopy/tomography.

  19. Coded ultrasound for blood flow estimation using subband processing

    DEFF Research Database (Denmark)

    Gran, F.; Udesen, J.; Jensen, J.A.;

    2008-01-01

    This paper investigates the use of coded excitation for blood flow estimation in medical ultrasound. Traditional autocorrelation estimators use narrow-band excitation signals to provide sufficient signal-to-noise-ratio (SNR) and velocity estimation performance. In this paper, broadband coded sign...

  20. Regional cerebral blood flow in fibromyalgia

    Energy Technology Data Exchange (ETDEWEB)

    Kwiatek, R.; Barnden, L.; Rowe, C.; McKinnon, J.; Pile, K. [The Queen Elizabeth Hospital , Adelaide, SA (Australia)

    1998-06-01

    Full text: Little is known of the aetiology of fibromyalgia (FM), a condition diagnosed on the basis of widespread chronic pain and multiple tender points. We have used Tc-99m HMPAO SPECT to compare regional cerebral bloodflow (rCBF) in 17 women who fulfill American College of Rheumatology criteria for FM to 22 age, sex and education matched controls. Both Statistical Parametric Mapping (SPM95) and coregistered MRI guided ROI were used for analysis. SPM95 revealed statistically significant hypoperfusion in the pontine tegmentum (p=0.048) and a trend to hypoperfusion in the left putamen (p=0.07). MRI guided ROI placement by an operator blinded to clinical information and the coregistered SPECT images, confirmed significant hypoperfusion of the left thalamus (p<0.0001) and the pontine tegmentum (p=0.001) and revealed trends towards hypoperfusion in the caudate nuclei and right thalamus. These results are consistent with the hypothesis that FM is due to dysfunction of central pain pathways. Spinothalamic neurones are known to be involved in pain perception and there are synapse connections to the thalamus in the gigantocellular part of the medulla and pons

  1. Differences in superior thyroid artery and inferior thyroid artery blood flow spectrum parameters in subacute thyroiditis

    Institute of Scientific and Technical Information of China (English)

    Jin-Bo Li

    2016-01-01

    Objective:To study the differences in superior thyroid artery and inferior thyroid artery blood flow spectrum parameters in subacute thyroiditis. Methods:A Total of 40 cases of patients with subacute thyroiditis and 40 cases of healthy volunteers were selected for study and enrolled in pathology group and control group respectively, color Doppler ultrasonography was conducted to detect peak blood flow velocities (Vmax) of superior thyroid artery and inferior thyroid artery as well as resistance index (RI), and serum was collected to detect thyroid hormone contents, infection indexes and oxidative stress indexes. Results:Peak blood flow velocities Vmax of superior thyroid artery and inferior thyroid artery of pathology group were significantly higher than those of control group, and resistance index RI was not different from that of control group;FT3, FT4, TT3, TT4, ESR, CRP, PCT and MDA of pathology group were significantly higher than those of control group, and SOD and TAOC were significantly lower than those of control group;Vmax of superior thyroid artery and inferior thyroid artery were positively correlated with FT3, FT4, TT3, TT4, ESR, CRP, PCT and MDA, and negatively correlated with SOD and TAOC. Conclusion:Peak blood flow velocities (Vmax) of superior thyroid artery and inferior thyroid artery in subacute thyroiditis are significantly accelerated, Vmax has good consistency with thyroid hormone contents, infection indexes and oxidative stress indexes, and it can accurately assess the severity of the disease.

  2. Noninvasive pulsatile flow estimation for an implantable rotary blood pump.

    Science.gov (United States)

    Karantonis, Dean M; Cloherty, Shaun L; Mason, David G; Ayre, Peter J; Lovell, Nigel H

    2007-01-01

    A noninvasive approach to the task of pulsatile flow estimation in an implantable rotary blood pump (iRBP) has been proposed. Employing six fluid solutions representing a range of viscosities equivalent to 20-50% blood hematocrit (HCT), pulsatile flow data was acquired from an in vitro mock circulatory loop. The entire operating range of the pump was examined, including flows from -2 to 12 L/min. Taking the pump feedback signals of speed and power, together with the HCT level, as input parameters, several flow estimate models were developed via system identification methods. Three autoregressive with exogenous input (ARX) model structures were evaluated: structures I and II used the input parameters directly; structure II incorporated additional terms for HCT; and the third structure employed as input a non-pulsatile flow estimate equation. Optimal model orders were determined, and the associated models yielded minimum mean flow errors of 5.49% and 0.258 L/min for structure II, and 5.77% and 0.270 L/min for structure III, when validated on unseen data. The models developed in this study present a practical method of accurately estimating iRBP flow in a pulsatile environment.

  3. Quantitating error in blood flow measurements with radioactive microspheres

    Energy Technology Data Exchange (ETDEWEB)

    Austin, R.E. Jr.; Hauck, W.W.; Aldea, G.S.; Flynn, A.E.; Coggins, D.L.; Hoffman, J.I.

    1989-07-01

    Accurate determination of the reproducibility of measurements using the microsphere technique is important in assessing differences in blood flow to different organs or regions within organs, as well as changes in perfusion under various experimental conditions. The sources of error of the technique are briefly reviewed. In addition, we derived a method for combining quantifiable sources of error into a single estimate that was evaluated experimentally by simultaneously injecting eight or nine sets of microspheres (each with a different radionuclide label) into four anesthetized dogs. Each nuclide was used to calculate blood flow in 145-190 myocardial regions. We compared each flow determination (using a single nuclide label) with a weighted mean for the piece (based on the remaining nuclides). The difference was defined as ''measured'' error. In all, there were a total of 5,975 flow observations. We compared measured error with theoretical estimates based on the Poisson error of radioactive disintegration and microsphere entrapment, nuclide separation error, and reference flow error. We found that combined estimates based on these sources completely accounted for measured error in the relative distribution of microspheres. In addition, our estimates of the error in measuring absolute flows (which were established using microsphere reference samples) slightly, but significantly, underestimated measured error in absolute flow.

  4. Microheterogeneity of blood flow in the rat urinary bladder

    Energy Technology Data Exchange (ETDEWEB)

    Kimura, Takahiro [Kawasaki Medical School, Kurashiki, Okayama (Japan)

    2002-08-01

    The microheterogeneity of blood flow in the mucous membrane of the urinary bladder and that in the detrusor muscle in anesthetized rats (n=8) were investigated at an extremely high spatial resolution (0.1 x 0.1 mm{sup 2}) using digital radiography combined with the {sup 3}H-labeled desmethylimipramine deposition technique. The spatial pattern of flow distribution was quantified by the coefficient of variation regional flow (CV: standard deviation/mean). The results showed muscle blood flow to be lower than mucous blood flow (muscle: mucosa=2.9:5), with the distribution of the former being more heterogeneous than that of the latter (CV in muscle vs. CV in mucosa=0.33{+-}0.033 vs. 0.16{+-}0.019, p<0.001) at the capillary level. It was therefore considered that the muscle would more easily experience mechanical irritation and be more easily influenced by arterial tonus than the mucous membrane, ant it was thought that this difference reflected a difference in regional perfusion. (author)

  5. Role of nitric oxide and prostanoids in the regulation of leg blood flow and blood pressure in humans with essential hypertension: effect of high-intensity aerobic training

    DEFF Research Database (Denmark)

    Nyberg, Michael Permin; Jensen, Lasse Gliemann; Thaning, Pia

    2012-01-01

    We examined the role of nitric oxide (NO) and prostanoids in the regulation of leg blood flow and systemic blood pressure before and after 8 weeks of aerobic high-intensity training in individuals with essential hypertension (n=10) and matched healthy control subjects (n=11). Hypertensive subjects...

  6. Unsteady flow about a circulation control airfoil

    Institute of Scientific and Technical Information of China (English)

    刘晶昌; 孙茂; 吴礼义

    1996-01-01

    The unsteady flow around a circulation control (CC) airfoil was investigated with Navier-Stokes method,which includes the flow around CC airfoil with pulsating jet,the flow around oscillating CC airfoil,and the flow around oscillating CC airfoil with pulsating jet.Dynamic properties of the flow and the aerodynamic forces were rewaled.

  7. Simulation of red blood cell aggregation in shear flow.

    Science.gov (United States)

    Lim, B; Bascom, P A; Cobbold, R S

    1997-01-01

    A simulation model has been developed for red blood cell (RBC) aggregation in shear flow. It is based on a description of the collision rates of RBC, the probability of particles sticking together, and the breakage of aggregates by shear forces. The influence of shear rate, hematocrit, aggregate fractal dimension, and binding strength on aggregation kinetics were investigated and compared to other theoretical and experimental results. The model was used to simulate blood flow in a long large diameter tube under steady flow conditions at low Reynolds numbers. The time and spatial distribution of the state of aggregation are shown to be in qualitative agreement with previous B-mode ultrasound studies in which a central region of low echogenicity was noted. It is suggested that the model can provide a basis for interpreting prior measurements of ultrasound echogenicity and may help relate them to the local state of aggregation.

  8. Quantitative blood flow velocity imaging using laser speckle flowmetry

    Science.gov (United States)

    Nadort, Annemarie; Kalkman, Koen; van Leeuwen, Ton G.; Faber, Dirk J.

    2016-04-01

    Laser speckle flowmetry suffers from a debated quantification of the inverse relation between decorrelation time (τc) and blood flow velocity (V), i.e. 1/τc = αV. Using a modified microcirculation imager (integrated sidestream dark field - laser speckle contrast imaging [SDF-LSCI]), we experimentally investigate on the influence of the optical properties of scatterers on α in vitro and in vivo. We found a good agreement to theoretical predictions within certain limits for scatterer size and multiple scattering. We present a practical model-based scaling factor to correct for multiple scattering in microcirculatory vessels. Our results show that SDF-LSCI offers a quantitative measure of flow velocity in addition to vessel morphology, enabling the quantification of the clinically relevant blood flow, velocity and tissue perfusion.

  9. Blood flow in the cerebral venous system: modeling and simulation.

    Science.gov (United States)

    Miraucourt, Olivia; Salmon, Stéphanie; Szopos, Marcela; Thiriet, Marc

    2017-04-01

    The development of a software platform incorporating all aspects, from medical imaging data, through three-dimensional reconstruction and suitable meshing, up to simulation of blood flow in patient-specific geometries, is a crucial challenge in biomedical engineering. In the present study, a fully three-dimensional blood flow simulation is carried out through a complete rigid macrovascular circuit, namely the intracranial venous network, instead of a reduced order simulation and partial vascular network. The biomechanical modeling step is carefully analyzed and leads to the description of the flow governed by the dimensionless Navier-Stokes equations for an incompressible viscous fluid. The equations are then numerically solved with a free finite element software using five meshes of a realistic geometry obtained from medical images to prove the feasibility of the pipeline. Some features of the intracranial venous circuit in the supine position such as asymmetric behavior in merging regions are discussed.

  10. Respiratory muscle blood flow during exercise: effects of sex and ovarian cycle.

    Science.gov (United States)

    Smith, Joshua R; Hageman, K Sue; Harms, Craig A; Poole, David C; Musch, Timothy I

    2017-01-26

    Sex and ovarian cycle have been speculated to modify respiratory muscle(s) blood flow control during exercise, but the findings are inconclusive. We tested the hypotheses that females would have higher respiratory muscle blood flow and vascular conductance (VC) compared to males during exercise and that this difference would be accentuated in proestrus versus ovariectomized (OVA) females. Mean arterial pressure (carotid artery catheter) and respiratory muscle blood flow (radiolabeled microspheres) were measured during moderate-intensity (24m/min, 10% grade) exercise in male (n=9), female (n=9), and OVA female (n=7) rats and near-maximal (60m/min, 5% grade) exercise in male (n=5) and female (n=7) rats. At rest, diaphragm, intercostal, and transversus abdominis blood flow were not different (p=0.33) among groups. During moderate-intensity exercise, diaphragm (M: 124±16; F: 140±14; OVA: 140±20mL/min/100g), intercostal (M: 33±5; F: 34±5; OVA: 30±5mL/min/100g), and transversus abdominis blood flow (M: 24±4; F: 35±7; OVA: 35±9mL/min/100g) significantly increased in all groups compared to rest, but were not different (p=0.12) among groups. From rest to moderate-intensity exercise, diaphragm (p0.13) existed in VC among groups. During near-maximal exercise, diaphragm (M: 304±62; F: 283±17mL/min/100g), intercostal (M: 29±8; F: 40±6mL/min/100g), and transversus abdominis (M: 85±14; F: 86±9mL/min/100g) blood flow and VC were not different (p>0.27) between males and females. These data demonstrate that respiratory muscle blood flow and vascular conductance at rest and during exercise are not affected by sex or ovarian cycle in rats.

  11. Noninvasive miniaturized mass-flow meter using a curved cannula for implantable axial flow blood pump.

    Science.gov (United States)

    Kosaka, Ryo; Nishida, Masahiro; Maruyama, Osamu; Yamane, Takashi

    2011-01-01

    Blood flow should be measured to monitor conditions of patients with implantable artificial hearts continuously and noninvasively. We have developed a noninvasive miniaturized mass-flow meter using a curved cannula for an axial flow blood pump. The mass-flow meter utilized centrifugal force generated by the mass-flow rate in the curved cannula. Two strain gauges served as sensors. Based on the numerical analysis, the first gauge, attached to the curved area, measured static pressure and centrifugal force, and the second, attached to the straight area, measured static pressure for static pressure compensation. The mass-flow rate was determined by the differences in output from the two gauges. To compensate for the inertia force under the pulsatile flow, a 0.75-Hz low-pass filter was added to the electrical circuit. In the evaluation tests, numerical analysis and an actual measurement test using bovine blood were performed to evaluate the measurement performances. As a result, in the numerical analysis, the relationship between the differential pressure caused by centrifugal force and the flow rate was verified. In the actual measurement test, measurement error was less than ± 0.5 L/min, and the time delay was 0.12 s. We confirmed that the developed mass-flow meter was able to measure mass-flow rate continuously and noninvasively.

  12. Blood flow simulation on a role for red blood cells in platelet adhesion

    Science.gov (United States)

    Shimizu, Kazuya; Sugiyama, Kazuyasu; Takagi, Shu

    2016-11-01

    Large-scale blood flow simulations were conducted and a role for red blood cells in platelet adhesion was discussed. The flow conditions and hematocrit values were set to the same as corresponding experiments, and the numerical results were compared with the measurements. Numerical results show the number of platelets adhered on the wall is increased with the increase in hematocrit values. The number of adhered platelets estimated from the simulation was approximately 28 (per 0.01 square millimeter per minute) for the hematocrit value of 20%. These results agree well with the experimental results qualitatively and quantitatively, which proves the validity of the present numerical model including the interaction between fluid and many elastic bodies and the modeling of platelet adhesion. Numerical simulation also reproduces the behavior of red blood cells in the blood flow and their role in platelet adhesion. Red blood cells deform to a flat shape and move towards channel center region. In contrast, platelets are pushed out and have many chances to contact with the wall. As a result, the large number of adhered platelets is observed as hematocrit values becomes high. This result indicates the presence of red blood cells plays a crucial role in platelet adhesion.

  13. Cerebral blood flow in migraine and cortical spreading depression

    Energy Technology Data Exchange (ETDEWEB)

    Lauritzen, M.

    1987-01-01

    In a series of migraine patients, carotid arteriography was carried out as part of the clinical evalution. Nine patients developed a migrainous attack with focal neurological symptoms and headache after the angiography and during the subsequent, ongoing regional cerebral blood flow rCBF study. rCBF was measured by bolus injection of Xenon/sup 133/ into the internal carotid artery and a gamma camera with 254 collimated scintillation detectors covering the lateral aspect of the hemisphere. This technique depicts rCBF mainly at the level of the superficial cortex, with no depth resolution. The resolution is 1 cm/sup 2/ providing detailed spatial information of the cortical blood flow. Other methods for measuring local blood flow in animal and man employ a radioactive, freely diffusible tracer, in combination with an autoradiographic technique for the assessment of the tissue concentration, the so-called autoradiographic methods. In the series of patients with spontaneous migraine, rCBF was estimated using an in-vivo application of the autoradiographic principle. Xenon/sup 133/ was administered by inhalation and the time course of the arterial concentration curve was assessed by a scintillation detector over the upper right lung, since the arterial curve has been found to follow the shape of the lung curve. The rCBF was studied accompanying cortical spreading depression in rat experiments to evaluate wheter this phenomenon could explain the blood flow changes in migraine. (/sup 14/C) iodoantipyrine was given as an intravenous bolus injection and the brain content of indicator was determined by tissue sample or autoradiography after 10 or 20 seconds of isotope circulation. The conditions of the autoradiographic methods are that the flow remains constant within the period of measuring, and that the region under study is homogenous with regard to flow and lambda. (EG).

  14. Assessment of maternal cerebral blood flow in patients with preeclampsia

    Directory of Open Access Journals (Sweden)

    Mandić Vesna

    2005-01-01

    Full Text Available Introduction Systemic vasoconstrktion in preeclamptic patients increases vascular resistance, and is manifested by increased arterial blood flow velocity. The aim of the study is to evaluate if there is a change of Doppler indices in maternal medial cerbral artery (MCA in severe preeclampsia due to: 1 severity of clinical symptoms, 2 the beginning of eclamptic attack and 3 the application of anticonvidsive therapy. Material and methods A prospective clinical study included 92 pregnant women, gestational age 28-36 weeks. They were divided into three groups: normotensive (n=30, mild preeclampsia (n=33, and severe preeclampsia (n=29. We investigated maternal cerebral circulation by assessing the MCA. We registrated: pulsatility index (Pi, resistance index (Ri, Systolic/diastolic ratio (S/D, and the maximum systolic, end diastolic and medium velocity. Patients with severe preeclampsia were divided into two subgroups: subgroup 1 included patients without symptoms of threatening eclampsia (n=18; 62.06%; while subgroup 2 included those with symptoms of preeclampsia (n=11; 37.94%. All patients with severe preeclampsia were treated with magnesium sulfate (MgSO4, and cerebral blood flow was measured before and after the treatment. Statistical analysis was done by oneway ANOVA, Student t-test and t-paired sample test. The difference was considered to be significant if p < 0.05. Results Significantly increased Pi, Ri and all velocities were established in the group of patients with severe preeclampsia compared with the other two groups. In the group with severe preeclamsia we registrated significantly increased values of all velocities (patients with signs of threatening eclampsia. After MgSO4 treatment in patients with severe preeclampsia significantly decreased values of Pi, Ri, S/D ratio and all velocities were registered. Discussion In the studied group of patients with severe preclampsia we found increased velocity values, Pi and Ri, especially in

  15. Skeletal blood flow, iliac histomorphometry, and strontium kinetics in osteoporosis: a relationship between blood flow and corrected apposition rate

    Energy Technology Data Exchange (ETDEWEB)

    Reeve, J.; Arlot, M.; Wootton, R.; Edouard, C.; Tellez, M.; Hesp, R.; Green, J.R.; Meunier, P.J.

    1988-06-01

    In 20 untreated patients with idiopathic or postmenopausal osteoporosis, kinetic studies of skeletal blood flow (using /sup 18/F) and bone turnover (using /sup 85/Sr) were combined with dynamic histomorphometry performed on transiliac biopsies taken within 6 weeks of each other. In 8 patients the combined studies were repeated after treatment. A further 5 patients were studied only while receiving treatment. As expected, skeletal blood flow measured by /sup 18/F correlated with an index of /sup 85/Sr uptake into the exchangeable pools of bone. Additionally and independently, skeletal blood flow correlated with an index of the work rate of the osteoblasts in each multicellular unit of bone (the corrected apposition rate of Parfitt). These correlations were statistically significant in both the untreated patients (P less than 0.05) and the whole group (P less than 0.001). Further indices related to bone turnover at the level of the skeleton as a whole were significantly associated with skeletal blood flow only in the combined group.

  16. VOST Flow-Control Valve Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A cryogenic flow-control valve based on Venturi-Offset Technology (VOST) will be designed and modeled. VOST provides precise linear flow control within a...

  17. Lattice Boltzmann Simulation of Blood Flow in Blood Vessels with the Rolling Massage

    Institute of Scientific and Technical Information of China (English)

    YI Hou-Hui; XU Shi-Xiong; QIAN Yue-Hong; FANG Hai-Ping

    2005-01-01

    @@ The rolling massage manipulation is a classic Chinese massage, which is expected to improve the circulation by pushing, pulling and kneading of the muscle. A model for the rolling massage manipulation is proposed and the lattice Boltzmann method is applied to study the blood flow in the blood vessels. The simulation results show that the blood flux is considerably modified by the rolling massage and the explicit value depends on the rolling frequency, the rolling depth, and the diameter of the vessel. The smaller the diameter of the blood vessel, the larger the enhancement of the blood flux by the rolling massage. The model, together with the simulation results,is expected to be helpful to understand the mechanism and further development of rolling massage techniques.

  18. A pilot study of regional cerebral blood flow in children with school phobia

    Institute of Scientific and Technical Information of China (English)

    钱昀

    2006-01-01

    Objective To explore the characteristics of the regional cerebral blood flow (rCBF) in children with school phobia. Methods The single - photon emission commputed tomography were performed in 17 children with school phobia and 11 normal controls. The rCBF distribution in regions of interest (ROIs) was compared

  19. Intraoperative vascular anatomy, arterial blood flow velocity, and microcirculation in unilateral and bilateral cleft lip repair

    NARCIS (Netherlands)

    Mueller, A.A.; Schumann, D.; Reddy, R.R.; Schwenzer-Zimmerer, K.; Mueller-Gerbl, M.; Zeilhofer, H.F.; Sailer, H.F.; Reddy, S.G.

    2012-01-01

    BACKGROUND: Cleft lip repair aims to normalize the disturbed anatomy and function. The authors determined whether normalization of blood circulation is achieved. METHODS: The authors measured the microcirculatory flow, oxygen saturation, and hemoglobin level in the lip and nose of controls (n = 22)

  20. The effect of the benzodiazepine antagonist flumazenil on regional cerebral blood flow in human volunteers

    DEFF Research Database (Denmark)

    Wolf, J; Friberg, L; Jensen, J

    1990-01-01

    The influence of the benzodiazepine antagonist flumazenil on regional cerebral blood flow (rCBF) was investigated in ten healthy, alert volunteers. The design was a randomized, placebo-controlled, double-blind, cross-over study. rCBF was measured by 133-Xe inhalation and single photon emission...

  1. MR assessment of absolute myocardial blood flow and vasodilator flow reserve in patients with hypertrophic cardiomyopathy

    Energy Technology Data Exchange (ETDEWEB)

    Kawada, Nanaka; Sakuma, Hajime; Takeda, Kan; Nakagawa, Tsuyoshi; Yamakado, Tetsu; Nakano, Takeshi [Mie Univ., Tsu (Japan). School of Medicine

    1997-04-01

    Absolute coronary blood flow per myocardial mass and coronary flow reserve for the entire left ventricle were evaluated in normals and in patients with hypertrophic cardiomyopathy (HCM) by using fast cine MR imaging and fast velocity encoded cine (VENC) MR imaging. Nine healthy volunteers and 8 patients with HCM were studied with a 1.5 T imager. Breath-hold cine MR images encompassing the whole left ventricle were acquired on short axis imaging planes in order to evaluate myocardial mass. A fast VENC MR images were obtained to measure blood flow volume in the coronary sinus before and after dipyridamole administration (TR/TE=15/5 ms, FOV=28 x 22 cm, slice thickness=5 mm). Coronary flow reserve was calculated as a ratio of hyperemic to baseline coronary flow volumes. In the baseline state, coronary blood flow per myocardial mass was significantly lower in patients with HCM than in normal myocardium (0.56{+-}0.23 vs. 0.78{+-}0.27 ml/min/g, p<0.05). After dipyridamole administration, coronary blood flow per myocardial mass in patients with HCM increased substantially less than that in healthy subjects (0.99{+-}0.38 vs. 2.22{+-}0.55 ml/min/g, p<0.01), resulting in the significantly decreased coronary flow reserve ratio in HCM in comparison with that in normal myocardium (1.86{+-}0.56 vs. 3.11{+-}1.37, p<0.05). In conclusion, breath-hold velocity encoded cine MR imaging is a noninvasive technique which can provide assessments of altered coronary blood flow volume per myocardial mass and vasodilator flow reserve in patients with HCM. (author)

  2. Structural analysis of red blood cell aggregates under shear flow.

    Science.gov (United States)

    Chesnutt, J K W; Marshall, J S

    2010-03-01

    A set of measures of red blood cell (RBC) aggregates are developed and applied to examine the aggregate structure under plane shear and channel flows. Some of these measures are based on averages over the set of red blood cells which are in contact with each other at a given time. Other measures are developed by first fitting an ellipse to the planar projection of the aggregate, and then examining the area and aspect ratio of the fit ellipse as well as the orientations of constituent RBCs with respect to the fit ellipse axes. The aggregate structural measures are illustrated using a new mesoscale computational model for blood cell transport, collision and adhesion. The sensitivity of this model to change in adhesive surface energy density and shear rate on the aggregate structure is examined. It is found that the mesoscale model predictions exhibit reasonable agreement with experimental and theoretical data for blood flow in plane shear and channel flows. The new structural measures are used to examine the differences between predictions of two- and three-dimensional computations of the aggregate formation, showing that two-dimensional computations retain some of the important aspects of three-dimensional computations.

  3. Laser speckle imaging of blood flow in microcirculation

    Energy Technology Data Exchange (ETDEWEB)

    Cheng Haiying; Luo Qingming; Liu Qian; Lu Qiang; Gong Hui; Zeng Shaoqun [Key Laboratory of Biomedical Photonics of Ministry of Education of China, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2004-04-07

    Monitoring the spatio-temporal characteristics of microcirculation is crucial for studying the functional activities of biotissue and the mechanism of disease. However, conventional methods used to measure blood flow suffer from limited spatial resolution or the injection of exogenous substances or the need of scanning to obtain the dynamic of regional blood flow. Laser speckle imaging (LSI) technique makes up these disadvantages by obtaining the regional blood flow distribution with high spatio-temporal resolution without the need to scan. In this paper, LSI was introduced to investigate the dynamic responses of the rat mesenteric microcirculation to an incremental dose of phentolamine. The results showed that when the dose of phentolamine was less than 4 {mu}g ml{sup -1}, local application of phentolamine on the mesentery would increase the blood perfusion as the concentration increased. When the dose increased further, the improvement decreased. At a dose of 200 {mu}g ml{sup -1}, a microcirculation impediment was caused. At the same time, different responses between veinules and arterioles were manifested. These suggested that LSI is promising to be a useful contribution to drug development and testing.

  4. Ozone Therapy on Cerebral Blood Flow: A Preliminary Report

    Directory of Open Access Journals (Sweden)

    Bernardino Clavo

    2004-01-01

    Full Text Available Ozone therapy is currently being used in the treatment of ischemic disorders, but the underlying mechanisms that result in successful treatment are not well known. This study assesses the effect of ozone therapy on the blood flow in the middle cerebral and common carotid arteries. Seven subjects were recruited for the therapy that was performed by transfusing ozone-enriched autologous blood on 3 alternate days over 1 week. Blood flow quantification in the common carotid artery (n = 14 was performed using color Doppler. Systolic and diastolic velocities in the middle cerebral artery (n = 14 were estimated using transcranial Doppler. Ultrasound assessments were conducted at the following three time points: 1 basal (before ozone therapy, 2 after session #3 and 3 1 week after session #3. The common carotid blood flow had increased by 75% in relation to the baseline after session #3 (P < 0.001 and by 29% 1 week later (P = 0.039. In the middle cerebral artery, the systolic velocity had increased by 22% after session #3 (P = 0.001 and by 15% 1 week later (P = 0.035, whereas the diastolic velocity had increased by 33% after session #3 (P < 0.001 and by 18% 1 week later (P = 0.023. This preliminary Doppler study supports the clinical experience of achieving improvement by using ozone therapy in peripheral ischemic syndromes. Its potential use as a complementary treatment in cerebral low perfusion syndromes merits further clinical evaluation.

  5. Blood flow dynamics, atherosclerosis and bypass graft failure.

    Science.gov (United States)

    Langille, B L; Ojha, M

    1997-05-01

    Atherosclerosis occurs at reproducible sites in the arterial tree and intimal proliferation that leads to bypass graft occlusion also show a well-defined focal distribution. These observations have led to the hypothesis that local blood flow conditions, especially low or fluctuating shear stresses, are important in the development of both disorders. Basic research using both cell culture and animal models has revealed that endothelial cell biology is very sensitive to local shear stresses and rapid progress is being made in characterizing how endothelial cells transduce shear stress. Endothelial sensitivity to shear stress affects control of hemostasis, leukocyte adherence and transmigration, growth factor production, vasomotor responses, endothelial repair and arterial wall remodeling, all of which can be expected to influence development of vascular pathologies. Also, substantial progress has been made in characterizing complex local hemodynamics at relevant arterial sites; however, further progress is needed in this area, as well as in the extrapolation of advances in basic vascular biology to human vascular disease. (Trends Cardiovasc Med 1997;7:111-118). © 1997, Elsevier Science Inc.

  6. Chronic impairment of leg muscle blood flow following cardiac catheterization in childhood. [/sup 133/Xe clearance measurements

    Energy Technology Data Exchange (ETDEWEB)

    Skovranek, J.; Samanek, M.

    1979-01-01

    In 99 patients with congenital heart defects or chronic respiratory disease without clinical symptoms of disturbances in peripheral circulation, resting and maximal blood flow in the anterior tibial muscle of both extremities were investigated 2.7 yrs (average) after cardiac catheterization. The method used involved /sup 133/Xe clearance. Resting blood flow was normal and no difference could be demonstrated between the extremity originally used for catheterization and the contralateral control extremity. No disturbance in maximal blood flow could be proved in the extremity used for catheterization by the venous route only. Maximal blood flow was significantly lower in that extremity where the femoral artery had been catheterized or cannulated for pressure measurement and blood sampling. The disturbance in maximal flow was shown regardless of whether the arterial catheterization involved the Seldinger percutaneous technique, arteriotomy, or mere cannulation of the femoral artery. The values in the involved extremity did not differ significantly from the values in a healthy population.

  7. Nitric oxide in the nucleus raphe magnus modulates cutaneous blood flow in rats during hypothermia

    Directory of Open Access Journals (Sweden)

    Masoumeh Kourosh Arami

    2015-10-01

    Full Text Available Objective(s: Nucleus Raphe Magnus (NRM that is involved in the regulation of body temperature contains nitric oxide (NO synthase. Considering the effect of NO on skin blood flow control, in this study, we assessed its thermoregulatory role within the raphe magnus. Materials and Methods: To this end, tail blood flow of male Wistar rats was measured by laser doppler following the induction of hypothermia. Results: Intra-NRM injection of SNP (exogenous NO donor, 0.1- 0.2 μl, 0.2 nM increased the blood flow. Similarly, unilateral microinjection of glutamate (0.1- 0.2 μl, 2.3 nM into the nucleus increased the blood flow. This effectof L-glutamate was reduced by prior intra NRM administrationof NO synthase inhibitor NG-methyl-L-arginine or NG-nitro-L-argininemethyl ester (L-NAME, 0.1 µl, 100 nM. Conclusion: It is concluded that NO modulates the thermoregulatory response of NRM to hypothermia and may interactwith excitatory amino acids in central skin blood flow regulation.

  8. Moderate exercise training promotes adaptations in coronary blood flow and adenosine production in normotensive rats

    Directory of Open Access Journals (Sweden)

    Fernanda R. Roque

    2011-01-01

    Full Text Available OBJECTIVES: Aerobic exercise training prevents cardiovascular risks. Regular exercise promotes functional and structural adaptations that are associated with several cardiovascular benefits. The aim of this study is to investigate the effects of swimming training on coronary blood flow, adenosine production and cardiac capillaries in normotensive rats. METHODS: Wistar rats were randomly divided into two groups: control (C and trained (T. An exercise protocol was performed for 10 weeks and 60 min/day with a tail overload of 5% bodyweight. Coronary blood flow was quantified with a color microsphere technique, and cardiac capillaries were quantified using light microscopy. Adenine nucleotide hydrolysis was evaluated by enzymatic activity, and protein expression was evaluated by western blot. The results are presented as the means ± SEMs (p<0.05. RESULTS: Exercise training increased the coronary blood flow and the myocardial capillary-to-fiber ratio. Moreover, the circulating and cardiac extracellular adenine nucleotide hydrolysis was higher in the trained rats than in the sedentary rats due to the increased activity and protein expression of enzymes, such as E-NTPDase and 59- nucleotidase. CONCLUSIONS: Swimming training increases coronary blood flow, number of cardiac capillaries, and adenine nucleotide hydrolysis. Increased adenosine production may be an important contributor to the enhanced coronary blood flow and angiogenesis that were observed in the exercise-trained rats; collectively, these results suggest improved myocardial perfusion.

  9. A Reconstruction Method of Blood Flow Velocity in Left Ventricle Using Color Flow Ultrasound

    Directory of Open Access Journals (Sweden)

    Jaeseong Jang

    2015-01-01

    Full Text Available Vortex flow imaging is a relatively new medical imaging method for the dynamic visualization of intracardiac blood flow, a potentially useful index of cardiac dysfunction. A reconstruction method is proposed here to quantify the distribution of blood flow velocity fields inside the left ventricle from color flow images compiled from ultrasound measurements. In this paper, a 2D incompressible Navier-Stokes equation with a mass source term is proposed to utilize the measurable color flow ultrasound data in a plane along with the moving boundary condition. The proposed model reflects out-of-plane blood flows on the imaging plane through the mass source term. The boundary conditions to solve the system of equations are derived from the dimensions of the ventricle extracted from 2D echocardiography data. The performance of the proposed method is evaluated numerically using synthetic flow data acquired from simulating left ventricle flows. The numerical simulations show the feasibility and potential usefulness of the proposed method of reconstructing the intracardiac flow fields. Of particular note is the finding that the mass source term in the proposed model improves the reconstruction performance.

  10. Cerebral blood flow in Alzheimer’s disease

    Directory of Open Access Journals (Sweden)

    Roher AE

    2012-10-01

    Full Text Available Alex E Roher,1 Josef P Debbins,2 Michael Malek-Ahmadi,3 Kewei Chen,4 James G Pipe,2 Sharmeen Maze,2 Christine Belden,3 Chera L Maarouf,1 Pradeep Thiyyagura,4 Hua Mo,4 Jesse M Hunter,1 Tyler A Kokjohn,1,5 Douglas G Walker,6 Jane C Kruchowsky,6 Marek Belohlavek,7 Marwan N Sabbagh,3 Thomas G Beach81The Longtine Center for Neurodegenerative Biochemistry, Banner Sun Health Research Institute, Sun City, 2Keller Center for Imaging Innovation, Neuroimaging Research, Barrow Neurological Institute, Phoenix, 3Cleo Roberts Center for Clinical Research, Banner Sun Health Research Institute, Sun City, 4Computational Image Analysis Program, Banner Alzheimer’s Institute, Phoenix, 5Department of Microbiology, Midwestern University, Glendale, 6Laboratory of Neuroinflammation, Banner Sun Health Research Institute, Sun City, 7Division of Cardiovascular Diseases, Mayo Clinic, Scottsdale, 8Civin Laboratory for Neuropathology, Banner Sun Health Research Institute, Sun City, AZ, USABackground: Alzheimer’s disease (AD dementia is a consequence of heterogeneous and complex interactions of age-related neurodegeneration and vascular-associated pathologies. Evidence has accumulated that there is increased atherosclerosis/arteriosclerosis of the intracranial arteries in AD and that this may be additive or synergistic with respect to the generation of hypoxia/ischemia and cognitive dysfunction. The effectiveness of pharmacologic therapies and lifestyle modification in reducing cardiovascular disease has prompted a reconsideration of the roles that cardiovascular disease and cerebrovascular function play in the pathogenesis of dementia.Methods: Using two-dimensional phase-contrast magnetic resonance imaging, we quantified cerebral blood flow within the internal carotid, basilar, and middle cerebral arteries in a group of individuals with mild to moderate AD (n = 8 and compared the results with those from a group of age-matched nondemented control (NDC subjects (n = 9

  11. Narcolepsy: regional cerebral blood flow during sleep and wakefulness

    Energy Technology Data Exchange (ETDEWEB)

    Sakai, F.; Meyer, J.S.; Karacan, I.; Yamaguchi, F.; Yamamoto, M.

    1979-01-01

    Serial measurements of regional cerebral blood flow were made by the 135Xe inhalation method during the early stages of sleep and wakefulness in eight normal volunteers and 12 patients with narcolepsy. Electroencephalogram, electro-oculogram, and submental electromyogram were recorded simultaneously. In normals, mean hemispheric gray matter blood flow (Fg) during stages I and II sleep was significantly less than waking values. Maximum regional blood flow decreases during sleep occurred in the brainstem-cerebellar, right inferior temporal, and bilateral frontal regions. In patients with narcolepsy, mean hemispheric Fg while awake was 80.5 +- 13 ml per 100 gm brain per minute. During REM sleep, mean hemispheric Fg increased concurrently with large increases in brainstem-cerebellar region flow. During stages I and II sleep without REM, there were significant increases in mean hemispheric Fg and brainstem-cerebellar Fg, just the opposite of changes in normals. In narcolepsy, there appears to be a reversal of normal cerebral deactivation patterns, particularly involving the brainstem, during stages I and II sleep.

  12. Occlusion-free Blood Flow Animation with Wall Thickness Visualization.

    Science.gov (United States)

    Lawonn, Kai; Glaßer, Sylvia; Vilanova, Anna; Preim, Bernhard; Isenberg, Tobias

    2016-01-01

    We present the first visualization tool that combines pathlines from blood flow and wall thickness information. Our method uses illustrative techniques to provide occlusion-free visualization of the flow. We thus offer medical researchers an effective visual analysis tool for aneurysm treatment risk assessment. Such aneurysms bear a high risk of rupture and significant treatment-related risks. Therefore, to get a fully informed decision it is essential to both investigate the vessel morphology and the hemodynamic data. Ongoing research emphasizes the importance of analyzing the wall thickness in risk assessment. Our combination of blood flow visualization and wall thickness representation is a significant improvement for the exploration and analysis of aneurysms. As all presented information is spatially intertwined, occlusion problems occur. We solve these occlusion problems by dynamic cutaway surfaces. We combine this approach with a glyph-based blood flow representation and a visual mapping of wall thickness onto the vessel surface. We developed a GPU-based implementation of our visualizations which facilitates wall thickness analysis through real-time rendering and flexible interactive data exploration mechanisms. We designed our techniques in collaboration with domain experts, and we provide details about the evaluation of the technique and tool.

  13. Axial dispersion in flowing red blood cell suspensions

    Science.gov (United States)

    Podgorski, Thomas; Losserand, Sylvain; Coupier, Gwennou

    2016-11-01

    A key parameter in blood microcirculation is the transit time of red blood cells (RBCs) through an organ, which can influence the efficiency of gas exchange and oxygen availability. A large dispersion of this transit time is observed in vivo and is partly due to the axial dispersion in the flowing suspension. In the classic Taylor-Aris example of a solute flowing in a tube, the combination of molecular diffusion and parabolic velocity profile leads to enhanced axial dispersion. In suspensions of non-Brownian deformable bodies such as RBCs, axial dispersion is governed by a combination of shear induced migration and shear-induced diffusion arising from hydrodynamic interactions. We revisit this problem in the case of RBC pulses flowing in a microchannel and show that the axial dispersion of the pulse eventually saturates with a final extension that depends directly on RBC mechanical properties. The result is especially interesting in the dilute limit since the final pulse length depends only on the channel width, exponent of the migration law and dimensionless migration velocity. In continuous flow, the dispersion of transit times is the result of complex cell-cell and cell-wall interactions and is strongy influenced by the polydispersity of the blood sample. The authors acknowledge support from LabEx TEC21 and CNES.

  14. In vivo photoacoustic imaging of transverse blood flow using Doppler broadening of bandwidth

    OpenAIRE

    Yao, Junjie; Maslov, Konstantin I.; Shi, Yunfei; Taber, Larry A.; Lihong V. Wang

    2010-01-01

    A new method is proposed to measure transverse blood flow using photoacoustic Doppler broadening of bandwidth. By measuring bovine blood flowing through a plastic tube, the linear dependence of the broadening on the flow speed was validated. The blood flow of the microvasculature in a mouse ear and a chicken embryo (stage 16) was also studied.

  15. In vivo photoacoustic imaging of transverse blood flow by using Doppler broadening of bandwidth

    OpenAIRE

    Yao, Junjie; Maslov, Konstantin I.; Shi, Yunfei; Taber, Larry A.; Lihong V. Wang

    2010-01-01

    A method is proposed to measure transverse blood flow by using photoacoustic Doppler broadening of bandwidth. By measuring bovine blood flowing through a plastic tube, the linear dependence of the broadening on the flow speed was validated. The blood flow of the microvasculature in a mouse ear and a chicken embryo (stage 16) was also studied.

  16. Transfer function analysis for the assessment of cerebral autoregulation using spontaneous oscillations in blood pressure and cerebral blood flow

    NARCIS (Netherlands)

    Abeelen, A.S.S. van den; Beek, A.H. van; Slump, C.H.; Panerai, R.B.; Claassen, J.A.H.R.

    2014-01-01

    Cerebral autoregulation (CA) is a key mechanism to protect the brain against excessive fluctuations in blood pressure (BP) and maintain cerebral blood flow. Analyzing the relationship between spontaneous BP and cerebral blood flow velocity (CBFV) using transfer function analysis is a widely used tec

  17. Phasic reflux of pulmonary blood flow in atelectasis: influence of systemic PO2.

    Science.gov (United States)

    Newell, J C; Levitzky, M G; Krasney, J A; Dutton, R E

    1976-06-01

    In 16 dogs ventilated with 100% O2, control blood flow to the left lung was 35 +/- 2% of aortic flow. When left lung atelectasis was induced, left pulmonary artery flow fell to 19 +/- 2% of aortic flow. A large retrograde component of flow developed in this pulmonary artery, suggesting that blood flows into the pulmonary arteries of both lungs during systole, but flows back out of the collapsed lung and into the uncollapsed lung during diastole. Systemic PaO2 remained above 78 mmHg. Subsequently, when the ventilation of the right lung was changed from oxygen to room air, systemic PaO2 fell to 64 +/- 3 mmHg and atelectatic left lung flow rose from 19 +/- 2% to 28 +/- 2% f aortic flow. This was associated with a reduction in reflux from the atelectatic lung. These results suggest that the attenuation of flow to an atelectatic lung is more pronounced if systemic normoxemia is maintained by adequate oxygenation of the normal lung.

  18. Blood Flow Imaging in Maternal and Fetal Arteries and Veins

    Science.gov (United States)

    Ricci, S.; Urban, G.; Vergani, P.; Paidas, M. J.; Tortoli, P.

    Maternal and fetal blood circulation has been investigated for nearly a decade through ultrasound (US) techniques. Evaluation of the spectrogram related to a single sample volume has been proven valuable for the assessment of fetal well-being and for prediction of pregnancy complications. In this work, an alternative technique, called Multigate Spectral Doppler Analysis (MSDA), is proposed. In this approach, 128 sample volumes aligned along the same scan line are simultaneously investigated to detect the blood velocity profile with high resolution. Profiles obtained through MSDA reveal features not detectable with the standard US technique, thus representing a more accurate flow signature. Some preliminary illustrative results are reported here.

  19. Effect of pregnancy on regional cerebral blood flow

    Energy Technology Data Exchange (ETDEWEB)

    Nagamachi, Shigeki; Hoshi, Hiroaki; Jinnouchi, Seishi; Ohnishi, Takashi; Futami, Shigemi; Watanabe, Katsushi; Ikeda, Tomoaki; Mori, Norimasa [Miyazaki Medical Coll., Kiyotake (Japan)

    1993-12-01

    Regional cerebral blood flow (r-CBF) of 10 pregnant women were quantified by {sup 133}Xe SPECT study with inhalation method before and after artificial abortion. During pregnancy, value of r-CBF in each region except occipital lobe was significantly higher than that of the post abortion. Arterial blood gas was analyzed after SPECT procedure. P{sub co2} concentration increased significantly after artificial abortion. Although its mechanism is unknown, our preliminary work demonstrates that r-CBF increased by pregnancy. (author).

  20. Holographic laser Doppler imaging of pulsatile blood flow

    CERN Document Server

    Bencteux, Jeffrey; Kostas, Thomas; Bayat, Sam; Atlan, Michael

    2015-01-01

    We report on wide-field imaging of pulsatile motion induced by blood flow using heterodyne holographic interferometry on the thumb of a healthy volunteer, in real-time. Optical Doppler images were measured with green laser light by a frequency-shifted Mach-Zehnder interferometer in off-axis configuration. The recorded optical signal was linked to local instantaneous out-of-plane motion of the skin at velocities of a few hundreds of microns per second, and compared to blood pulse monitored by plethysmoraphy during an occlusion-reperfusion experiment.

  1. Tomographic cerebral blood flow measurement during carotid surgery

    DEFF Research Database (Denmark)

    Rathenborg, Lisbet Knudsen; Vorstrup, Sidsel; Olsen, K S

    1994-01-01

    OBJECTIVES: The aim of the study was to depict regional cerebral blood flow (rCBF) during carotid cross clamping using 99mTechnetium-hexamethylpropylene amine oxime (TcHMPAO). This tracer rapidly passes the blood-brain barrier and is retained for hours in the brain tissue. Injecting TcHMPAO during...... RESULTS: We found a significant correlation between stump pressure and enhancement of side-to-side asymmetry in rCBF due to carotid cross clamping. Pronounced variations were seen in which regions were deprived of perfusion during clamping. CONCLUSION: TcHMPAO allows tomographic assessment of CBF during...

  2. Involvement of calcitonin gene-related peptide in migraine: regional cerebral blood flow and blood flow velocity in migraine patients

    DEFF Research Database (Denmark)

    Lassen, L.H.; Jacobsen, V.B.; Haderslev, P.A.

    2008-01-01

    g/min) or placebo for 20 min was studied in 12 patients with migraine without aura outside attacks. Xenon-133 inhalation SPECT-determined regional cerebral blood flow (rCBF) and transcranial Doppler (TCD)-determined blood velocity (V-mean) in the middle cerebral artery (MCA), as well as the heart......Calcitonin gene-related peptide (CGRP)-containing nerves are closely associated with cranial blood vessels. CGRP is the most potent vasodilator known in isolated cerebral blood vessels. CGRP can induce migraine attacks, and two selective CGRP receptor antagonists are effective in the treatment...... of migraine attacks. It is therefore important to investigate its mechanism of action in patients with migraine. We here investigate the effects of intravenous human alpha-CGRP (h alpha CGRP) on intracranial hemodynamics. In a double-blind, cross-over study, the effect of intravenous infusion of haCGRP (2 mu...

  3. Preservation of Renal Blood Flow by the Antioxidant EUK-134 in LPS-Treated Pigs

    Directory of Open Access Journals (Sweden)

    Sheldon Magder

    2015-03-01

    Full Text Available Sepsis is associated with an increase in reactive oxygen species (ROS, however, the precise role of ROS in the septic process remains unknown. We hypothesized that treatment with EUK-134 (manganese-3-methoxy N,N'-bis(salicyclideneethylene-diamine chloride, a compound with superoxide dismutase and catalase activity, attenuates the vascular manifestations of sepsis in vivo. Pigs were instrumented to measure cardiac output and blood flow in renal, superior mesenteric and femoral arteries, and portal vein. Animals were treated with saline (control, lipopolysaccharide (LPS; 10 µg·kg−1·h−1, EUK-134, or EUK-134 plus LPS. Results show that an LPS-induced increase in pulmonary artery pressure (PAP as well as a trend towards lower blood pressure (BP were both attenuated by EUK-134. Renal blood flow decreased with LPS whereas superior mesenteric, portal and femoral flows did not change. Importantly, EUK-134 decreased the LPS-induced fall in renal blood flow and this was associated with a corresponding decrease in LPS-induced protein nitrotyrosinylation in the kidney. PO2, pH, base excess and systemic vascular resistance fell with LPS and were unaltered by EUK-134. EUK-134 also had no effect on LPS-associated increase in CO. Interestingly, EUK-134 alone resulted in higher CO, BP, PAP, mean circulatory filling pressure, and portal flow than controls. Taken together, these data support a protective role for EUK-134 in the renal circulation in sepsis.

  4. Preservation of renal blood flow by the antioxidant EUK-134 in LPS-treated pigs.

    Science.gov (United States)

    Magder, Sheldon; Parthenis, Dimitrios G; Ghouleh, Imad Al

    2015-03-25

    Sepsis is associated with an increase in reactive oxygen species (ROS), however, the precise role of ROS in the septic process remains unknown. We hypothesized that treatment with EUK-134 (manganese-3-methoxy N,N'-bis(salicyclidene)ethylene-diamine chloride), a compound with superoxide dismutase and catalase activity, attenuates the vascular manifestations of sepsis in vivo. Pigs were instrumented to measure cardiac output and blood flow in renal, superior mesenteric and femoral arteries, and portal vein. Animals were treated with saline (control), lipopolysaccharide (LPS; 10 µg·kg-1·h-1), EUK-134, or EUK-134 plus LPS. Results show that an LPS-induced increase in pulmonary artery pressure (PAP) as well as a trend towards lower blood pressure (BP) were both attenuated by EUK-134. Renal blood flow decreased with LPS whereas superior mesenteric, portal and femoral flows did not change. Importantly, EUK-134 decreased the LPS-induced fall in renal blood flow and this was associated with a corresponding decrease in LPS-induced protein nitrotyrosinylation in the kidney. PO2, pH, base excess and systemic vascular resistance fell with LPS and were unaltered by EUK-134. EUK-134 also had no effect on LPS-associated increase in CO. Interestingly, EUK-134 alone resulted in higher CO, BP, PAP, mean circulatory filling pressure, and portal flow than controls. Taken together, these data support a protective role for EUK-134 in the renal circulation in sepsis.

  5. Non-Invasive Monitoring of Temporal and Spatial Blood Flow during Bone Graft Healing Using Diffuse Correlation Spectroscopy.

    Directory of Open Access Journals (Sweden)

    Songfeng Han

    Full Text Available Vascular infiltration and associated alterations in microvascular blood flow are critical for complete bone graft healing. Therefore, real-time, longitudinal measurement of blood flow has the potential to successfully predict graft healing outcomes. Herein, we non-invasively measure longitudinal blood flow changes in bone autografts and allografts using diffuse correlation spectroscopy in a murine femoral segmental defect model. Blood flow was measured at several positions proximal and distal to the graft site before implantation and every week post-implantation for a total of 9 weeks (autograft n = 7 and allograft n = 10. Measurements of the ipsilateral leg with the graft were compared with those of the intact contralateral control leg. Both autografts and allografts exhibited an initial increase in blood flow followed by a gradual return to baseline levels. Blood flow elevation lasted up to 2 weeks in autografts, but this duration varied from 2 to 6 weeks in allografts depending on the spatial location of the measurement. Intact contralateral control leg blood flow remained at baseline levels throughout the 9 weeks in the autograft group; however, in the allograft group, blood flow followed a similar trend to the graft leg. Blood flow difference between the graft and contralateral legs (ΔrBF, a parameter defined to estimate graft-specific changes, was elevated at 1-2 weeks for the autograft group, and at 2-4 weeks for the allograft group at the proximal and the central locations. However, distal to the graft, the allograft group exhibited significantly greater ΔrBF than the autograft group at 3 weeks post-surgery (p < 0.05. These spatial and temporal differences in blood flow supports established trends of delayed healing in allografts versus autografts.

  6. Effects of Kaempferia parviflora extracts on reproductive parameters and spermatic blood flow in male rats.

    Science.gov (United States)

    Chaturapanich, G; Chaiyakul, S; Verawatnapakul, V; Pholpramool, C

    2008-10-01

    Krachaidum (KD, Kaempferia parviflora Wall. Ex. Baker), a native plant of Southeast Asia, is traditionally used to enhance male sexual function. However, only few scientific data in support of this anecdote have been reported. The present study investigated the effects of feeding three different extracts of KD (alcohol, hexane, and water extracts) for 3-5 weeks on the reproductive organs, the aphrodisiac activity, fertility, sperm motility, and blood flow to the testis of male rats. Sexual performances (mount latency, mount frequency, ejaculatory latency, post-ejaculatory latency) and sperm motility were assessed by a video camera and computer-assisted sperm analysis respectively, while blood flow to the testis was measured by a directional pulsed Doppler flowmeter. The results showed that all extracts of KD had virtually no effect on the reproductive organ weights even after 5 weeks. However, administration of the alcohol extract at a dose of 70 mg/kg body weight (BW)/day for 4 weeks significantly decreased mount and ejaculatory latencies when compared with the control. By contrast, hexane and water extracts had no influence on any sexual behavior parameters. All types of extracts of KD had no effect on fertility or sperm motility. On the other hand, alcohol extract produced a significant increase in blood flow to the testis without affecting the heart rate and mean arterial blood pressure. In a separate study, an acute effect of alcohol extract of KD on blood flow to the testis was investigated. Intravenous injection of KD at doses of 10, 20, and 40 mg/kg BW caused dose-dependent increases in blood flow to the testis. The results indicate that alcohol extract of KD had an aphrodisiac activity probably via a marked increase in blood flow to the testis.

  7. Influence of preinfarction angina and coronary collateral blood flow on the efficacy of remote ischaemic conditioning in patients with ST segment elevation myocardial infarction: post hoc subgroup analysis of a randomised controlled trial

    Science.gov (United States)

    Pryds, Kasper; Bøttcher, Morten; Sloth, Astrid Drivsholm; Munk, Kim; Rahbek Schmidt, Michael; Bøtker, Hans Erik

    2016-01-01

    Objectives Remote ischaemic conditioning (RIC) confers cardioprotection in patients with ST segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (pPCI). We investigated whether preinfarction angina and coronary collateral blood flow (CCBF) to the infarct-related artery modify the efficacy of RIC. Design Post hoc subgroup analysis of a randomised controlled trial. Participants A total of 139 patients with STEMI randomised to treatment with pPCI or RIC+pPCI. Interventions RIC was performed prior to pPCI as four cycles of 5 min upper arm ischaemia and reperfusion with a blood pressure cuff. Primary outcome measure Myocardial salvage index (MSI) assessed by single-photon emission computerised tomography. We evaluated the efficacy of RIC in subgroups of patients with or without preinfarction angina or CCBF. Results Of 139 patients included in the study, 109 had available data for preinfarction angina status and 54 had preinfarction angina. Among 83 patients with Thrombolysis In Myocardial Infarction flow 0/1 on arrival, 43 had CCBF. Overall, RIC+pPCI increased median MSI compared with pPCI alone (0.75 vs 0.56, p=0.045). Mean MSI did not differ between patients with and without preinfarction angina in either the pPCI alone (0.58 and 0.57; 95% CI −0.17 to 0.19, p=0.94) or the RIC+pPCI group (0.66 and 0.69; 95% CI −0.18 to 0.10, p=0.58). Mean MSI did not differ between patients with and without CCBF in the pPCI alone group (0.51 and 0.55; 95% CI −0.20 to 0.13, p=0.64), but was increased in patients with CCBF versus without CCBF in the RIC+pPCI group (0.75 vs 0.58; 95% CI 0.03 to 0.31, p=0.02; effect modification from CCBF on the effect of RIC on MSI, p=0.06). Conclusions Preinfarction angina did not modify the efficacy of RIC in patients with STEMI undergoing pPCI. CCBF to the infarct-related artery seems to be of importance for the cardioprotective efficacy of RIC. Trial registration number NCT00435266, Post

  8. Blood plasma separation in a long two-phase plug flowing through disposable tubing.

    Science.gov (United States)

    Sun, Meng; Khan, Zeina S; Vanapalli, Siva A

    2012-12-21

    We report a simple technique to separate plasma from blood in a flowing immiscible plug. We investigate the effect of various control parameters such as blood dilution, injection flow rate, observation time and fluid properties on plasma separation. We find that the technique works best for diluted blood samples at low plug velocities and long observation times. We postulate that the main mechanism responsible for efficient separation is the sedimentation of blood cells in the plug and their subsequent collection by the moving plug causing a significant accumulation of cells at the rear of the plug. We discuss the time scales determining the sedimentation, advection and collection of a blood cell in the immiscible plug and propose a phase diagram that is able to predict the operating space for effective plasma separation. We demonstrate that the technique allows for the extraction of more than 60% of the plasma by volume from 1 μL of diluted blood. We show the practical significance of this method by compartmentalizing the separated plasma into discrete microfluidic droplets and detecting cholesterol. This technique features low consumption of blood (nL-scale) and low shear rate (∼1 s(-1)). It is inexpensive, easy to use, and has the potential to be developed as an efficient point-of-care device for blood diagnostics in resource-poor environments. More advanced applications could also be envisioned by integrating our plasma separation method into existing microfluidic drop manipulation techniques.

  9. Case with stenosis of internal carotid artery detected as a region of decreased blood flow by Tc-99m HMPAO cerebral blood flow scintigraphy

    Energy Technology Data Exchange (ETDEWEB)

    Hayashida, K.; Nishimura, T.; Uehara, T.; Imakita, S.; Yokota, I.; Ogura, H.; Oka, H.; Hayashi, M.; Kikuchi, H.

    1987-04-01

    Tc-99m hexamethylpropyleneamine oxime (= HMPAO) is expected to be an excellent agent as blood flow tracer of brain because it passes through blood brain barrier and is retained in brain parenchyma for several hours. Tc-99m HMPAO scintigraphy was applied to a patient complaining of transient ischemic attack without neurological findings. Left hemispheric hypoperfusion was detected by Tc-99m HMPAO cerebral blood flow scintigraphy. Although it was normal in CT and MRI, it was proved to be a 99 % stenosis of left internal carotid artery by digital subtraction angiography. Tc-99m HMPAO cerebral blood flow scintigraphy is useful for detecting abnormality of cerebral blood flow.

  10. Fractal regional myocardial blood flows pattern according to metabolism, not vascular anatomy.

    Science.gov (United States)

    Yipintsoi, Tada; Kroll, Keith; Bassingthwaighte, James B

    2016-02-01

    Regional myocardial blood flows are markedly heterogeneous. Fractal analysis shows strong near-neighbor correlation. In experiments to distinguish control by vascular anatomy vs. local vasomotion, coronary flows were increased in open-chest dogs by stimulating myocardial metabolism (catecholamines + atropine) with and without adenosine. During control states mean left ventricular (LV) myocardial blood flows (microspheres) were 0.5-1 ml·g(-1)·min(-1) and increased to 2-3 ml·g(-1)·min(-1) with catecholamine infusion and to ∼4 ml·g(-1)·min(-1) with adenosine (Ado). Flow heterogeneity was similar in all states: relative dispersion (RD = SD/mean) was ∼25%, using LV pieces 0.1-0.2% of total. During catecholamine infusion local flows increased in proportion to the mean flows in 45% of the LV, "tracking" closely (increased proportionately to mean flow), while ∼40% trended toward the mean. Near-neighbor regional flows remained strongly spatially correlated, with fractal dimension D near 1.2 (Hurst coefficient 0.8). The spatial patterns remain similar at varied levels of metabolic stimulation inferring metabolic dominance. In contrast, adenosine vasodilation increased flows eightfold times control while destroying correlation with the control state. The Ado-induced spatial patterns differed from control but were self-consistent, inferring that with full vasodilation the relaxed arterial anatomy dominates the distribution. We conclude that vascular anatomy governs flow distributions during adenosine vasodilation but that metabolic vasoregulation dominates in normal physiological states.

  11. Regional cerebral blood flow abnormalities in patients with primary hyperparathyroidism

    Energy Technology Data Exchange (ETDEWEB)

    Cermik, Tevfik F. [Hospital of the University of Trakya, Department of Nuclear Medicine, Edirne (Turkey); Trakya Universitesi Hastanesi, Nukleer Tip Anabilim Dali, Gullapoglu Yerleskesi, Edirne (Turkey); Kaya, Meryem; Bedel, Deniz; Berkarda, Sakir; Yigitbasi, Oemer N. [Hospital of the University of Trakya, Department of Nuclear Medicine, Edirne (Turkey); Ugur-Altun, Betuel [Hospital of the University of Trakya, Department of Internal Medicine, Division of Endocrinology, Edirne (Turkey)

    2007-04-15

    We assessed the alterations in regional cerebral blood flow (rCBF) in patients with primary hyperparathyroidism (PHP) before parathyroidectomy by semiquantitative analysis of brain single photon emission computed tomography (SPECT) images. Included in this prospective study were 14 patients (mean age 47.6 {+-} 10.4 years; 3 male, 11 female) and 10 control subjects (mean age 36.0 {+-} 8.5 years, 6 male, 4 female) were SPECT imaging was performed using a dual-headed gamma camera 60-90 min after intravenous administration of 925 MBq Tc-99m HMPAO. The corticocerebellar rCBF ratios were calculated from 52 brain areas and reference lower values (RLVs) were calculated from the rCBF ratios of control subjects. The regional ratios that were below the corresponding RLV were considered abnormal (hypoperfused). Hypoperfusion was shown in 171 out of 728 regions (23%) and there was a significant correlation between serum calcium, PTH levels and the sum of hypoperfused regions in the patient group (R = 0.75 and P = 0.001, and R = 0.75, P = 0.001, respectively). Significantly reduced rCBF were found in the following cortical regions: bilateral cingulate cortex, superior and inferior frontal cortex, anterior temporal cortex, precentral gyrus, postcentral gyrus and parietal cortex, and right posterior temporal cortex. Our results indicate that alterations in rCBF in patients with PHP can be demonstrated with brain SPECT. The correlation between serum calcium, PTH levels and the sum of hypoperfused regions indicates that there may be a strong relationship between rCBF abnormalities and increased levels of serum calcium and PTH. In addition, the degree of rCBF abnormalities could be determined by brain SPECT in PHP patients with or without psychiatric symptoms. (orig.)

  12. Encircling endocardial ventriculotomy for refractory ischemic ventricular tachycardia. II. Effects on regional myocardial blood flow.

    Science.gov (United States)

    Ungerleider, R M; Holman, W L; Stanley, T E; Lofland, G K; Williams, J M; Smith, P K; Quick, G; Cox, J L

    1982-06-01

    Previous experimental studies of the encircling endocardial ventriculotomy (EEV) have shown a significant alteration of normal local electrical activity within the encompassed region. Although this procedure may result in isolation of ventricular arrhythmias, the data are more suggestive of a less specific effect on regional myocardial blood flow. This study examines the effect of EEV on local myocardial blood flow using the radioactive tracer microsphere technique in 10 dogs. Flows were determined before and after an EEV with the animals on cardiopulmonary bypass at controlled perfusion pressures, temperatures, and heart rates. Blood flow was studied at subepicardial and subendocardial levels inside, outside, and bordering the EEV. Prior to performance of the EEV, subepicardial blood flow in the left ventricular myocardium ranged from 0.81 +/- 0.07 to 0.89 +/- 0.08 ml/gm/min. Subendocardial flows ranged from 0.80 +/- 0.07 to 0.91 +/- 0.09 ml/gm/min. There was no significant difference between any of the flows across each respective layer of myocardium. Following the EEV procedure, blood flow to the subendocardium within the EEV fell to 0.33 +/- 0.07 ml/gm/min, while flow to the subendocardium of the normal regions of the same hearts actually increased to 1.21 +/- 0.23 ml/gm/min. Similar changes occurred at subepicardial levels, with flow at the center of the EEV falling to 0.66 +/- 0.10 ml/gm/min despite a tendency for normal subepicardial flow to increase to 1.78 +/- 0.24 ml/gm/min. Superimposed ischemia to the EEV-encompassed myocardium, created by occlusion of the distal left anterior descending coronary artery (LAD), accentuated this abnormality by demonstrating that the region continues to receive some flow from epicardially based coronary vessels. The data from this study show that the EEV decreased regional blood flow to the encompassed myocardium and suggests that myocardial ischemia may be responsible for ablation of the delicate re-entrant mechanisms

  13. Patterns of fetal lamb regional cerebral blood flow during and after prolonged hypoxia.

    Science.gov (United States)

    Ashwal, S; Majcher, J S; Vain, N; Longo, L D

    1980-10-01

    In an effort to determine to what extent cerebral blood flow (CBF) varies in different parts of the brain during prolonged fetal hypoxia, we measured flow to 34 regions in 12 chronically catheterized fetal lambs 130 to 140 days gestation. Control values of PO2, PCO2 pH, heart rate, and blood pressure were obtained, and CBF was measured by use of radioactive labeled microspheres during a control period, during (15-, 30-, and 90-min) reduction of maternal inspired O2 concentration (fetal arterial PO2 was maintained at 12 to 15 torr), and 60 min after returning the ewe to room air. control blood flow to cortical, subcortical, and brainstem structures equaled 134, 186, and 254 ml x min-1 x 100 g-1, respectively. During hypoxia, CBF increased 92%, and 60 min after fetal oxygenation was restored, it remained 50% above control values. We noted a similar response in regional CBF to the cortex, subcortex, and brainstem during and after hypoxia. Blood flow to smaller areas within the three major regions were quite homogenous and had a similar pattern of response to hypoxia. We conclude that: (1) significant fetal regional CBF differences occurred in utero with brainstem and subcortical flows being substantially greater than flows to other regions of the brain; (2) during prolonged intrauterine hypoxia, total regional CBF increased 92%; (3) 1 hr after fetal oxygenation was restored, CBF still remained 50% above control values; and finally, (4) there was no significant preferential shunting of regional CBF during prolonged hypoxia in utero.

  14. Pressure Gradient Estimation Based on Ultrasonic Blood Flow Measurement

    Science.gov (United States)

    Nitta, Naotaka; Homma, Kazuhiro; Shiina, Tsuyoshi

    2006-05-01

    Mechanical load to the blood vessel wall, such as shear stress and pressure, which occurs in blood flow dynamics, contribute greatly to plaque rupture in arteriosclerosis and to biochemical activation of endothelial cells. Therefore, noninvasive estimations of these mechanical loads are able to provide useful information for the prevention of vascular diseases. Although the pressure is the dominant component of mechanical load, for practical purposes, the pressure gradient is also often important. So far, we have investigated the estimation of the kinematic viscosity coefficient using a combination of the Navier-Stokes equations and ultrasonic velocity measurement. In this paper, a method for pressure gradient estimation using the estimated kinematic viscosity coefficient is proposed. The validity of the proposed method was investigated on the basis of the analysis with the data obtained by computer simulation and a flow phantom experiment. These results revealed that the proposed method can provide a valid estimation of the pressure gradient.

  15. Chronic intestinal ischemia and splanchnic blood-flow

    DEFF Research Database (Denmark)

    Zacho, Helle Damgaard; Henriksen, Jens Henrik; Abrahamsen, Jan

    2013-01-01

    -1390), and this value increased significantly to 1787 mL/min after the meal in healthy volunteers (P ...-induced increase in SBF was equal to 282 mL/min + 5.4 mL/min × bodyweight, (P = 0.025). The SO₂U in healthy volunteers and patients was 50.7 mL/min and 48.0 mL/min, respectively, and these values increased to 77.5 mL/min and 75 mL/min postprandially, respectively. Both baseline and postprandial SO₂U were directly......AIM: To determine the splanchnic blood flow and oxygen uptake in healthy-subjects and patients and to relate the findings to body-composition. METHODS: The total splanchnic blood flow (SBF) and oxygen uptake (SO₂U) were measured in 20 healthy volunteers (10 women) and 29 patients with suspected...

  16. High speed optical holography of retinal blood flow.

    Science.gov (United States)

    Pellizzari, M; Simonutti, M; Degardin, J; Sahel, J-A; Fink, M; Paques, M; Atlan, M

    2016-08-01

    We performed noninvasive video imaging of retinal blood flow in a pigmented rat by holographic interferometry of near-infrared laser light backscattered by retinal tissue, beating against an off-axis reference beam sampled at a frame rate of 39 kHz with a high throughput camera. Local Doppler contrasts emerged from the envelopes of short-time Fourier transforms and the phase of autocorrelation functions of holograms rendered by Fresnel transformation. This approach permitted imaging of blood flow in large retinal vessels (∼30 microns diameter) over 400×400  pixels with a spatial resolution of ∼8 microns and a temporal resolution of ∼6.5  ms.

  17. Clitoral blood flow increases following vaginal pressure stimulation.

    Science.gov (United States)

    Lavoisier, P; Aloui, R; Schmidt, M H; Watrelot, A

    1995-02-01

    The vascular responses of clitoral arteries to vaginal pressure stimulation in 10 volunteer women were evaluated by Doppler ultrasonography. Pressure stimulations (20-160 mm Hg) along the lower third of the vagina increased blood velocity and flow into clitoral arteries in 9 of the 10 women. The latency and duration of the Doppler responses ranged from 0.1 to 1.6 sec and from 3.2 to 9.5 sec, respectively, and the response was associated with a blood flow increase of 4 to 11 times the baseline prestimulation level. This response parallels that recorded in the cavernous arteries in men when a similar range of pressure stimulations are applied to the glans penis. Similar responses evoked in the male and female suggest a sexual synergy that may occur during intercourse in that such physiological responses and reflexes may be reciprocally reinforced.

  18. Peripheral blood flow control in diabetes mellitus

    DEFF Research Database (Denmark)

    Hilsted, Jannik

    1991-01-01

    Long term diabetes has a profound effect on the peripheral circulation. This has been demonstrated to be due to the presence of angiopathy and autonomic neuropathy, affecting autoregulation and distensibility of the vessels as well as local and central reflex regulation of the vascular resistance...

  19. Unsteady magnetohydrodynamic blood flow through irregular multi-stenosed arteries.

    Science.gov (United States)

    Mustapha, Norzieha; Amin, Norsarahaida; Chakravarty, Santabrata; Mandal, Prashanta Kumar

    2009-10-01

    Flow of an electrically conducting fluid characterizing blood through the arteries having irregular shaped multi-stenoses in the environment of a uniform transverse magnetic-field is analysed. The flow is considered to be axisymmetric with an outline of the irregular stenoses obtained from a three-dimensional casting of a mild stenosed artery, so that the physical problem becomes more realistic from the physiological point of view. The marker and cell (MAC) and successive-over-relaxation (SOR) methods are respectively used to solve the governing unsteady magnetohydrodynamic (MHD) equations and pressure-Poisson equation quantitatively and to observe the flow separation. The results obtained show that the flow separates mostly towards the downstream of the multi-stenoses. However, the flow separation region keeps on shrinking with the increasing intensity of the magnetic-field which completely disappears with sufficiently large value of the Hartmann number. The present observations certainly have some clinical implications relating to magnetotherapy which help reducing the complex flow separation zones causing flow disorder leading to the formation and progression of the arterial diseases.

  20. Efficacy, Safety and Mechanisms of Blood Flow Restricted Exercise

    Science.gov (United States)

    Ploutz-Snyder, Lori

    2009-01-01

    This 20 minute talk will review studies in the peer-reviewed literature related to the effectiveness of blood flow restricted exercise as an exercise training program. There is controversy regarding the talk with cover the effectiveness of various exercise protocols and these differences will be compared and contrasted. Unpublished data from my laboratory at Syracuse University will be presented (see other abstract), as well as some unpublished work from the labs of Manini, Clark and Rasmussen (none are NASA funded).

  1. Effect of TIPS placement on portal and splanchnic arterial blood flow in 4-dimensional flow MRI

    Energy Technology Data Exchange (ETDEWEB)

    Stankovic, Zoran [Northwestern University, Department of Radiology, Feinberg School of Medicine, Chicago, IL (United States); University Medical Center Freiburg, Department of Diagnostic Radiology and Medical Physics, Freiburg (Germany); Roessle, Martin; Schultheiss, Michael [University Medical Center Freiburg, Department of Gastroenterology, Freiburg (Germany); Euringer, Wulf; Langer, Mathias [University Medical Center Freiburg, Department of Diagnostic Radiology and Medical Physics, Freiburg (Germany); Salem, Riad; Barker, Alex; Carr, James; Collins, Jeremy D. [Northwestern University, Department of Radiology, Feinberg School of Medicine, Chicago, IL (United States); Markl, Michael [Northwestern University, Department of Radiology, Feinberg School of Medicine, Chicago, IL (United States); Northwestern University, Department of Biomedical Engineering, McCormick School of Engineering, Chicago, IL (United States)

    2015-09-15

    To assess changes in portal and splanchnic arterial haemodynamics in patients undergoing transjugular intrahepatic portosystemic shunt (TIPS) using four-dimensional (4D) flow MRI, a non-invasive, non-contrast imaging technique. Eleven patients undergoing TIPS implantation were enrolled. K-t GRAPPA accelerated non-contrast 4D flow MRI of the liver vasculature was applied with acceleration factor R = 5 at 3Tesla. Flow analysis included three-dimensional (3D) blood flow visualization using time-resolved 3D particle traces and semi-quantitative flow pattern grading. Quantitative evaluation entailed peak velocities and net flows throughout the arterial and portal venous (PV) systems. MRI measurements were taken within 24 h before and 4 weeks after TIPS placement. Three-dimensional flow visualization with 4D flow MRI revealed good image quality with minor limitations in PV flow. Quantitative analysis revealed a significant increase in PV flow (562 ± 373 ml/min before vs. 1831 ± 965 ml/min after TIPS), in the hepatic artery (176 ± 132 ml/min vs. 354 ± 140 ml/min) and combined flow in splenic and superior mesenteric arteries (770 ml/min vs. 1064 ml/min). Shunt-flow assessment demonstrated stenoses in two patients confirmed and treated at TIPS revision. Four-dimensional flow MRI might have the potential to give new information about the effect of TIPS placement on hepatic perfusion. It may explain some unexpected findings in clinical observation studies. (orig.)

  2. Retinal blood flow velocity in patients with active uveitis using the retinal function imager

    Institute of Scientific and Technical Information of China (English)

    FENG Xing; Kedhar Sanjay; Bhoomibunchoo Chavakij

    2013-01-01

    Background Previous studies suggest a link between macular edema and retinal blood flow velocity (RBFV).The effects of inflammation in the retinal blood vessels are not clearly understood.We want to evaluate the differences in retinal blood flow velocities of patients with active uveitis and healthy controls using the retinal function imager (RFI)and determine the correlation between retinal blood flow veiocity and central macular thickness in uveitis patients.Methods Twenty-eight eyes of 24 patients with active anterior uveitis and 51 eyes of 51 normal control subjects were enrolled.Retinal blood flow velocities evaluated by RFI and central macular thickness evaluated by optical coherence tomography (SLO-OCT) were obtained.Differences among the groups were assessed using Stata statistical software.Results Ten eyes had uveitic cystoid macular edema (CME).Median (first quartile,third quartile) venous velocity for uveitic eyes with CME,uveitic eyes without CME,and controls were 2.09 (1.92,2.44),2.64 (2.32,2.86),and 2.82 (2.39,3.53) mm/s respectively.Median (first and quartile) arterial velocity for uveitic eyes with CME,uveitic eyes without CME,and controls were 3.79 (3.61,4.09),3.46 (2.86,4.12),and 3.93 (3.35,4.65) mm/s.Uveitic eyes with CME had significantly lower venous velocity than controls (P=0.044).There was a strong linear relationship between venous velocity and central retinal thickness (P=-0.007).Conclusions Retinal venous velocities were significantly decreased in eyes with uveitic CME relative to controls.Decreased venous velocity was correlated with increased central retinal thickness in uveitic eyes.

  3. Predicting Endometrium Receptivity with Parameters of Spiral Artery Blood Flow

    Institute of Scientific and Technical Information of China (English)

    GONG Xuehao; LI Quanshui; ZHANG Qingping; ZHU Guijin

    2005-01-01

    Summary: In order To evaluate whether the parameters of spiral artery blood flow, as measured by transvaginal color Doppler, may be used to assess endometrium receptivity prior to embryo transfer (ET), a retrospective study of 94 infertile women who had undergone ART treatments with different outcomes (pregnant or nonpregnant) was done. Subendometrial blood flow was evaluated. The resistance index (RI), systolic/diastolic ratio (S/D) and pulsatility index (PI) were significantly lower in those who achieved pregnancy as compared with those who did not: 0.62±0.04 vs 0.68±0.04 (P<0.001), 2.66±0.33 vs 3.19±0.39 (P<0.01) and 1.15±0.17 vs 1.34±0.22 (P<0.05), respectively. Furthermore, when RI>0.72, PI>1.6, and S/D>3.6, no pregnancy occurred. These data suggest that the parameters of spiral artery blood flow could be used as a new assay in predicting endometrial receptivity before ET.

  4. Ocular Blood Flow Measured Noninvasively in Zero Gravity

    Science.gov (United States)

    Ansari, Rafat R.; Manuel, Francis K.; Geiser, Martial; Moret, Fabrice; Messer, Russell K.; King, James F.; Suh, Kwang I.

    2003-01-01

    In spaceflight or a reduced-gravity environment, bodily fluids shift to the upper extremities of the body. The pressure inside the eye, or intraocular pressure, changes significantly. A significant number of astronauts report changes in visual acuity during orbital flight. To date this remains of unknown etiology. Could choroidal engorgement be the primary mechanism and a change in the curvature or shape of the cornea or lens be the secondary mechanism for this change in visual acuity? Perfused blood flow in the dense meshwork of capillaries of the choroidal tissue (see the preceding illustration) provides necessary nutrients to the outer layers of the retina (photoreceptors) to keep it healthy and maintain good vision. Unlike the vascular system, the choroid has no baroreceptors to autoregulate fluid shifts, so it can remain engorged, pushing the macula forward and causing a hyperopic (farsighted) shift of the eye. Experiments by researchers at the NASA Glenn Research Center could help answer this question and facilitate planning for long-duration missions. We are investigating the effects of zero gravity on the choroidal blood flow of volunteer subjects. This pilot project plans to determine if choroidal blood flow is autoregulated in a reduced-gravity environment.

  5. Pulsed photoacoustic Doppler flow measurements in blood-mimicking phantoms

    Science.gov (United States)

    Brunker, J.; Beard, P.

    2011-03-01

    The feasibility of making spatially resolved measurements of blood flow using pulsed photoacoustic Doppler techniques has been explored. Doppler time shifts were quantified via cross-correlation of pairs of photoacoustic waveforms generated within a blood-simulating phantom using pairs of laser light pulses. The photoacoustic waves were detected using a focussed or planar PZT ultrasound transducer. For each flow measurement, a series of 100 waveform pairs was collected. Previous data processing methods involved rejection of poorly correlated waveform pairs; the modal velocity value and standard deviation were then extracted from the selected distribution of velocity measurements. However, the data selection criteria used in this approach is to some extent arbitrary. A new data analysis protocol, which involves averaging the 100 cross-correlation functions and thus uses all of the measured data, has been designed in order to prevent exclusion of outliers. This more rigorous approach has proved effective for quantifying the linear motion of micron-scale absorbers imprinted on an acetate sheet moving with velocities in the range 0.14 to 1.25 ms-1. Experimental parameters, such as the time separation between the laser pulses and the transducer frequency response, were evaluated in terms of their effect on the accuracy, resolution and range of measurable velocities. The technique was subsequently applied to fluid phantoms flowing at rates less than 5 mms-1 along an optically transparent tube. Preliminary results are described for three different suspensions of phenolic resin microspheres, and also for whole blood. Velocity information was obtained even under non-optimal conditions using a low frequency transducer and a low pulse repetition frequency. The distinguishing advantage of pulsed rather than continuous-wave excitation is that spatially resolved velocity measurements can be made. This offers the prospect of mapping flow within the microcirculation and thus

  6. Controlling Flow Turbulence Using Local Pinning Feedback

    Institute of Scientific and Technical Information of China (English)

    TANG Guo-Ning; HU Gang

    2006-01-01

    Flow turbulence control in two-dimensional Navier-Stokes equation is considered.By applying local pinning control only to a sjngle component of flow velocity field,the flow turbulence can be controlled to desirable targets.It is found that with certain number of controllers there exist an optimal control strength at which control error takes minimum value,and larger and smaller control strengths give worse control efficiency.The phvsical mechanism underlying these strange control results is analysed based on the interactions between different types of modes.

  7. Backstepping feedback control of open channel flow

    OpenAIRE

    Huo, Mandy; Malek, Sami

    2014-01-01

    We derive a feedback control law for the control of the downstream flow in a 1-D open channel by manipulating the water flow at an upstream location. We use backstepping for controller design and Lyapunov techniques for stability analysis. Finally, the controller is verified with simulations.

  8. Impaired autoregulation of blood flow in subcutaneous tissue of long-term type 1 (insulin-dependent) diabetic patients with microangiopathy

    DEFF Research Database (Denmark)

    Kastrup, J; Nørgaard, T; Parving, H H;

    1985-01-01

    Autoregulation of blood flow in subcutaneous tissue was studied at the level of the lateral malleolus in eight long-term Type 1 (insulin-dependent) diabetic patients with clinical microangiopathy, eight short-term Type 1 diabetic patients without clinical microangiopathy and seven healthy control...... by activation of the leg muscle vein pump (heel raising). Mean arterial blood pressure was thus varied between 60 and 160 mmHg. In normal and short-term diabetic subjects blood flow remained within 10% of control values during the changes in arterial blood pressure. In six of the eight Type 1 diabetic patients...... with clinical microangiopathy, autoregulation of blood flow was impaired, blood flow changing approximately 20% per 10 mmHg change in arterial blood pressure; the slope of the autoregulation curves was significantly higher compared with the two control groups (p less than 0.02). Resting mean arterial blood...

  9. Retrograde arterial leg blood flow during tilt-back from a head-up posture: importance of capacitive flows when arterial pressure changes.

    Science.gov (United States)

    Sheriff, Don D; Nådland, Inger Helene; Toska, Karin

    2010-03-01

    The windkessel function of the arterial system converts the intermittent action of the heart into more continuous microcirculatory blood flow during diastole via the return of elastic energy stored in the walls of the arteries during systole. Might the same phenomenon occur regionally within the arterial system during tilting owing to regional differences in local arterial pressure imposed by gravity? We sought to test the hypothesis that during tilt-back from a head-up posture, the return of stored elastic energy in leg arteries would work to slow, or perhaps transiently reverse, the flow of blood in the femoral artery. Femoral artery blood flow and arterial pressure were recorded during tilt back from a 30 degrees head-up posture to supine (approximately 0.5 G) in young, healthy subjects (n = 7 males and 3 females) before and during clonidine infusion. During control (no drug) conditions femoral artery blood flow ceased for an entire heart beat during tilt-back. During clonidine infusion femoral artery blood flow reversed for at least one entire heart beat during tilt-back, i.e., blood flow in the retrograde direction in the femoral artery from the leg into the abdomen. Thus substantial capacitive effects of tilting on leg blood flow occur in humans during mild changes in posture.

  10. Characterizing human skin blood flow regulation in response to different local skin temperature perturbations.

    Science.gov (United States)

    Wu, Y; Nieuwenhoff, M D; Huygen, F J P M; van der Helm, F C T; Niehof, S; Schouten, A C

    2017-05-01

    Small nerve fibers regulate local skin blood flow in response to local thermal perturbations. Small nerve fiber function is difficult to assess with classical neurophysiological tests. In this study, a vasomotor response model in combination with a heating protocol was developed to quantitatively characterize the control mechanism of small nerve fibers in regulating skin blood flow in response to local thermal perturbation. The skin of healthy subjects' hand dorsum (n=8) was heated to 42°C with an infrared lamp, and then naturally cooled down. The distance between the lamp and the hand was set to three different levels in order to change the irradiation intensity on the skin and implement three different skin temperature rise rates (0.03°C/s, 0.02°C/s and 0.01°C/s). A laser Doppler imager (LDI) and a thermographic video camera recorded the temporal profile of the skin blood flow and the skin temperature, respectively. The relationship between the skin blood flow and the skin temperature was characterized by a vasomotor response model. The model fitted the skin blood flow response well with a variance accounted for (VAF) between 78% and 99%. The model parameters suggested a similar mechanism for the skin blood flow regulation with the thermal perturbations at 0.03°C/s and 0.02°C/s. But there was an accelerated skin vasoconstriction after a slow heating (0.01°C/s) (p-value<0.05). An attenuation of the skin vasodilation was also observed in four out of the seven subjects during the slow heating (0.01°C/s). Our method provides a promising way to quantitatively assess the function of small nerve fibers non-invasively and non-contact.

  11. Rotating permanent magnet excitation for blood flow measurement.

    Science.gov (United States)

    Nair, Sarath S; Vinodkumar, V; Sreedevi, V; Nagesh, D S

    2015-11-01

    A compact, portable and improved blood flow measurement system for an extracorporeal circuit having a rotating permanent magnetic excitation scheme is described in this paper. The system consists of a set of permanent magnets rotating near blood or any conductive fluid to create high-intensity alternating magnetic field in it and inducing a sinusoidal varying voltage across the column of fluid. The induced voltage signal is acquired, conditioned and processed to determine its flow rate. Performance analysis shows that a sensitivity of more than 250 mV/lpm can be obtained, which is more than five times higher than conventional flow measurement systems. Choice of rotating permanent magnet instead of an electromagnetic core generates alternate magnetic field of smooth sinusoidal nature which in turn reduces switching and interference noises. These results in reduction in complex electronic circuitry required for processing the signal to a great extent and enable the flow measuring device to be much less costlier, portable and light weight. The signal remains steady even with changes in environmental conditions and has an accuracy of greater than 95%. This paper also describes the construction details of the prototype, the factors affecting sensitivity and detailed performance analysis at various operating conditions.

  12. Relationship between cardiac function and resting cerebral blood flow

    DEFF Research Database (Denmark)

    Henriksen, Otto M; Jensen, Lars T; Krabbe, Katja;

    2014-01-01

    Although both impaired cardiac function and reduced cerebral blood flow are associated with ageing, current knowledge of the influence of cardiac function on resting cerebral blood flow (CBF) is limited. The aim of this study was to investigate the potential effects of cardiac function on CBF. CBF...... and cardiac output were measured in 31 healthy subjects 50-75 years old using magnetic resonance imaging techniques. Mean values of CBF, cardiac output and cardiac index were 43.6 ml per 100 g min(-1), 5.5 l min(-1) and 2.7 l min(-1) m(-2), respectively, in males, and 53.4 ml per 100 g min(-1), 4.3 l min(-1......) and 2.4 l min(-1) m(-2), respectively, in females. No effects of cardiac output or cardiac index on CBF or structural signs of brain ageing were observed. However, fractional brain flow defined as the ratio of total brain flow to cardiac output was inversely correlated with cardiac index (r(2) = 0.22, P...

  13. In vivo evaluation of femoral blood flow measured with magnetic resonance

    DEFF Research Database (Denmark)

    Henriksen, O; Ståhlberg, F; Thomsen, C;

    1989-01-01

    Quantitative measurements of blood flow based on magnetic resonance imaging (MRI) using conventional multiple spin echo sequences were evaluated in vivo in healthy young volunteers. Blood flow was measured using MRI in the femoral vein. The initial slope of the multiple spin echo decay curve...... that in vivo blood flow measurements made with MRI based on wash-out effects, commonly used in multiple spin echo imaging, do not give reliable absolute values for blood flow in the femoral artery or vein......., corrected for the T2 decay of non-flowing blood was used to calculate the blood flow. As a reference, the blood flow in the femoral artery was measured simultaneously with an invasive indicator dilution technique. T2 of non-flowing blood was measured in vivo in popliteal veins during regional circulatory...

  14. Cerebral blood flow modulation insufficiency in brain networks in multiple sclerosis: A hypercapnia MRI study.

    Science.gov (United States)

    Marshall, Olga; Chawla, Sanjeev; Lu, Hanzhang; Pape, Louise; Ge, Yulin

    2016-12-01

    Cerebrovascular reactivity measures vascular regulation of cerebral blood flow and is responsible for maintaining healthy neurovascular coupling. Multiple sclerosis exhibits progressive neurodegeneration and global cerebrovascular reactivity deficits. This study investigates varied degrees of cerebrovascular reactivity impairment in different brain networks, which may be an underlying cause for functional changes in the brain, affecting long-distance projection integrity and cognitive function; 28 multiple sclerosis and 28 control subjects underwent pseudocontinuous arterial spin labeling perfusion MRI to measure cerebral blood flow under normocapnia (room air) and hypercapnia (5% carbon dioxide gas mixture) breathing. Cerebrovascular reactivity, measured as normocapnic to hypercapnic cerebral blood flow percent increase normalized by end-tidal carbon dioxide change, was determined from seven functional networks (default mode, frontoparietal, somatomotor, visual, limbic, dorsal, and ventral attention networks). Group analysis showed significantly decreased cerebrovascular reactivity in patients compared to controls within the default mode, frontoparietal, somatomotor, and ventral attention networks after multiple comparison correction. Regression analysis showed a significant correlation of cerebrovascular reactivity with lesion load in the default mode and ventral attention networks and with gray matter atrophy in the default mode network. Functional networks in multiple sclerosis patients exhibit varied amounts of cerebrovascular reactivity deficits. Such blood flow regulation abnormalities may contribute to functional communication disruption in multiple sclerosis.

  15. Effects of resveratrol alone or in combination with piperine on cerebral blood flow parameters and cognitive performance in human subjects: a randomised, double-blind, placebo-controlled, cross-over investigation

    OpenAIRE

    Wightman, Emma; Reay, Jonathon; Haskell, Crystal; Williamson, Gary; Dew, Tristan; Kennedy, David

    2014-01-01

    Previous research has shown that resveratrol can increase cerebral blood flow (CBF) in the absence of improved cognitive performance in healthy, young human subjects during the performance of cognitively demanding tasks. This lack of cognitive effects may be due to low bioavailability and, in turn, reduced bioefficacy of resveratrol in vivo. Piperine can alter polyphenol pharmacokinetics, but previous studies have not investigated whether this affects the efficacy of the target compound. Ther...

  16. Laser speckle contrast imaging to measure changes in cerebral blood flow.

    Science.gov (United States)

    Winship, Ian R

    2014-01-01

    Laser speckle contrast imaging (LSCI) is a powerful tool capable of acquiring detailed maps of blood flow in arteries and veins on the cortical surface. Based on the blurring of laser speckle patterns by the motion of blood cells, LSCI can be combined with a variety of optical imaging preparations to acquire high-spatiotemporal resolution images of blood flow, and track changes in blood flow over time, using relatively simple instrumentation. Here, we describe methods for LSCI of cerebral blood flow via a thin skull imaging preparation in mice or rats. This preparation allows precise semiquantitative mapping of changes in blood flow over time using straightforward surgical protocols and equipment.

  17. PERFUSION PRESSURE AND RENAL BLOOD FLOW: THEIR RELATIONSHIP AND DIFFERENCES

    Directory of Open Access Journals (Sweden)

    Carlos G. Musso, MD. PhD.1,2, Manuel Vilas, MD.

    2014-05-01

    Full Text Available The concepts of renal perfusion pressure (RPP and renal blood flow (RBF are usually confused, but although they are intimately related, they are not strictly the same. RPP originates from the minute cardiac volume and is, therefore, the cause of RBF, which generates glomerular filtration and as a consequence, also induces the urinary flow. On the other hand, whereas RPP can be subject to fluctuations, the same happens to RBF though at a much lower level due to the existence of physiological mechanisms, such as self-regulation of the flow and tubule-glomerular feed-back. We conclude that there is a dependence of the RBF in relation with RPP, with the former acting as the final responsible of the glomerular filtration.

  18. Renal blood flow and metabolism after cold ischaemia

    DEFF Research Database (Denmark)

    Henriksen, J H; Petersen, H K

    1984-01-01

    Peroperative measurements of renal blood flow (RBF), renal O2-uptake, and renal venous lactate/pyruvate (L/P) ratio were performed before and after a period of 30-71 min of hypothermic (10-15 degrees C) renal ischaemia in nine patients, undergoing surgery for renal calculi. Before ischaemia, RBF.......01) immediately after re-established perfusion and 36% (P less than 0.02) 30 min later. In one additional patient, who had a short warm ischaemia (8 min), the flow pattern was the same. As arterial pressure remained constant, the reduced RBF signifies an increased renal vascular resistance. Renal O2-uptake...... and renal venous L/P ratio were almost constant, indicating no significant anaerobic processes being involved in the flow response. None of the patients showed any signs of reactive hyperaemia. It is concluded that hypothermic renal ischaemia may be followed by an increased renal vascular resistance even...

  19. A model of blood flow in the mesenteric arterial system

    Directory of Open Access Journals (Sweden)

    Cheng Leo K

    2007-05-01

    Full Text Available Abstract Background There are some early clinical indicators of cardiac ischemia, most notably a change in a person's electrocardiogram. Less well understood, but potentially just as dangerous, is ischemia that develops in the gastrointestinal system. Such ischemia is difficult to diagnose without angiography (an invasive and time-consuming procedure mainly due to the highly unspecific nature of the disease. Understanding how perfusion is affected during ischemic conditions can be a useful clinical tool which can help clinicians during the diagnosis process. As a first step towards this final goal, a computational model of the gastrointestinal system has been developed and used to simulate realistic blood flow during normal conditions. Methods An anatomically and biophysically based model of the major mesenteric arteries has been developed to be used to simulate normal blood flows. The computational mesh used for the simulations has been generated using data from the Visible Human project. The 3D Navier-Stokes equations that govern flow within this mesh have been simplified to an efficient 1D scheme. This scheme, together with a constitutive pressure-radius relationship, has been solved numerically for pressure, vessel radius and velocity for the entire mesenteric arterial network. Results The computational model developed shows close agreement with physiologically realistic geometries other researchers have recorded in vivo. Using this model as a framework, results were analyzed for the four distinct phases of the cardiac cycle – diastole, isovolumic contraction, ejection and isovolumic relaxation. Profiles showing the temporally varying pressure and velocity for a periodic input varying between 10.2 kPa (77 mmHg and 14.6 kPa (110 mmHg at the abdominal aorta are presented. An analytical solution has been developed to model blood flow in tapering vessels and when compared with the numerical solution, showed excellent agreement. Conclusion An

  20. Blood pressure control for diabetic retinopathy

    Directory of Open Access Journals (Sweden)

    Diana V. Do

    Full Text Available BACKGROUND: Diabetic retinopathy is a common complication of diabetes and a leading cause of visual impairment and blindness. Research has established the importance of blood glucose control to prevent development and progression of the ocular complications of diabetes. Simultaneous blood pressure control has been advocated for the same purpose, but findings reported from individual studies have supported varying conclusions regarding the ocular benefit of interventions on blood pressure.OBJECTIVES: The primary aim of this review was to summarize the existing evidence regarding the effect of interventions to control or reduce blood pressure levels among diabetics on incidence and progression of diabetic retinopathy, preservation of visual acuity, adverse events, quality of life, and costs. A secondary aim was to compare classes of anti-hypertensive medications with respect to the same outcomes.METHODS:Search methods: We searched a number of electronic databases including CENTRAL as well as ongoing trial registries. We last searched the electronic databases on 25 April 2014. We also reviewed reference lists of review articles and trial reports selected for inclusion. In addition, we contacted investigators of trials with potentially pertinent data. Selection criteria: We included in this review randomized controlled trials (RCTs in which either type 1 or type 2 diabetic participants, with or without hypertension, were assigned randomly to intense versus less intense blood pressure control, to blood pressure control versus usual care or no intervention on blood pressure, or to different classes of anti-hypertensive agents versus placebo. Data collection and analysis: Pairs of review authors independently reviewed titles and abstracts from electronic and manual searches and the full text of any document that appeared to be relevant. We assessed included trials independently for risk of bias with respect to outcomes reported in this review. We

  1. Blood pressure control for diabetic retinopathy

    Science.gov (United States)

    Do, Diana V; Wang, Xue; Vedula, Satyanarayana S; Marrone, Michael; Sleilati, Gina; Hawkins, Barbara S; Frank, Robert N

    2015-01-01

    Background Diabetic retinopathy is a common complication of diabetes and a leading cause of visual impairment and blindness. Research has established the importance of blood glucose control to prevent development and progression of the ocular complications of diabetes. Simultaneous blood pressure control has been advocated for the same purpose, but findings reported from individual studies have supported varying conclusions regarding the ocular benefit of interventions on blood pressure. Objectives The primary aim of this review was to summarize the existing evidence regarding the effect of interventions to control or reduce blood pressure levels among diabetics on incidence and progression of diabetic retinopathy, preservation of visual acuity, adverse events, quality of life, and costs. A secondary aim was to compare classes of anti-hypertensive medications with respect to the same outcomes. Search methods We searched a number of electronic databases including CENTRAL as well as ongoing trial registries. We last searched the electronic databases on 25 April 2014. We also reviewed reference lists of review articles and trial reports selected for inclusion. In addition, we contacted investigators of trials with potentially pertinent data. Selection criteria We included in this review randomized controlled trials (RCTs) in which either type 1 or type 2 diabetic participants, with or without hypertension, were assigned randomly to intense versus less intense blood pressure control, to blood pressure control versus usual care or no intervention on blood pressure, or to different classes of anti-hypertensive agents versus placebo. Data collection and analysis Pairs of review authors independently reviewed titles and abstracts from electronic and manual searches and the full text of any document that appeared to be relevant. We assessed included trials independently for risk of bias with respect to outcomes reported in this review. We extracted data regarding trial

  2. Fetal blood flow measurements in severe rhesus isoimmunization. A case report.

    Science.gov (United States)

    Stiller, R J; Ashmead, G G; Paul, D; Weiner, S

    1987-06-01

    Maternal isoimmunization can result in fetal anemia. Current management of isoimmunized pregnancies involves amniocentesis and spectrophotometry. Pulsed Doppler ultrasound can provide fetal blood flow determinations from the fetal umbilical vein. A pregnancy complicated by severe rhesus isoimmunization was studied with Doppler ultrasound. Increased fetal umbilical blood flow was associated with increased fetal hemolysis. Umbilical vein blood flow decreased after intrauterine transfusion. Doppler ultrasound assessment of fetal blood flow is a useful noninvasive adjunct in isoimmunized pregnancies.

  3. Quantification of myocardial blood flow and blood flow reserve in the presence of arterial dispersion: a simulation study.

    Science.gov (United States)

    Schmitt, Melanie; Viallon, Magalie; Thelen, Manfred; Schreiber, Wolfgang G

    2002-04-01

    Myocardial blood flow (MBF) can be quantified using dynamic T1-weighted MRI of diffusible tracers and a mathematical model of underlying vasculature. Quantification of MBF by means of T1- weighted MRI requires knowledge of the arterial input function (AIF). The AIF can be estimated from the left ventricular (LV) cavity. However, dispersion may occur between the LV and the tissue of interest because of the laminar blood flow profiles, branching of venules, and because of stenosis. To evaluate the influence of dispersion on the results of MBF quantification, a simulation study was performed. The dispersion was described as a convolution of the AIF with an exponential residue function. Synthetic tissue and AIF curves were analyzed and the derived parameters fit to the simulated parameters. The results show that an unaccounted dispersion may result in a systematic underestimation of MBF up to approximately 50%. Underestimation increases with increasing dispersion and with increasing MBF. Assuming equal dispersion at rest and during hyperemia, myocardial perfusion reserve (MPR) estimates are also susceptible to underestimation of approximately 20%. An unaccounted dispersion therefore can lead to systematic underestimation of both blood flow and perfusion reserve.

  4. ASSESSMENT OF VERTEBRAL ARTERIES BLOOD FLOW SPECTRAL DOPPLER INDICES IN COMPARISON WITH INTERNAL AND COMMON CAROTID ARTERIES BLOOD FLOW SPECTRAL DOPPLER INDICES

    Directory of Open Access Journals (Sweden)

    H. Mazaher

    2007-05-01

    Full Text Available Vertebrobasilar insufficiency is the cause of cerebrovascular accidents in 20% of cases. There are few reports regarding spectral Doppler indices (SDIs of vertebral arteries (VAs normal blood flow. The objective of this study was to provide basic reference data about SDIs of VAs normal blood flow separately and in comparison with internal carotid arteries (ICAs and common carotid arteries (CCAs normal blood flows SDIs. This cross-sectional study performed on 70 normal patients. Color Doppler sonography (CDS and spectral Doppler sonography (SDS of right and left VAs (RVA and LVA, right and left CCAs (RCCA and LCCA, right and left ICAs (RICA and LICA, were performed. The mean PSV, EDV, and RI values of RVA blood flow were as 41.60 ± 9.6 cm/s, 14.60 ± 3.7 cm/s and 0.65 ± 0.06, and the mean PSV, EDV and RI values of LVA blood flow were as 42.20 ± 10.2 cm/s, 15.20 ± 4.2 cm/s, and 0.64 ± 0.05, respectively. There was not statistically significant difference between the mean PSV, EDV and RI values of RVA and LVA blood flows. The mean PSV and EDV values of VAs blood flows were significantly lower than the values of CCAs and ICCAs blood flows, respectively. The mean RI value of VAs blood flows was significantly lower than the mean RI Value of CCAs blood flows, but there was not statistically significant difference between the mean RI value of VAs blood flows and the mean RI value of ICAs blood flows.

  5. Cerebral blood flow assessment of preterm infants during respiratory therapy with the expiratory flow increase technique

    Directory of Open Access Journals (Sweden)

    Mariana Almada Bassani

    2016-06-01

    Full Text Available Abstract Objective: To assess the impact of respiratory therapy with the expiratory flow increase technique on cerebral hemodynamics of premature newborns. Methods: This is an intervention study, which included 40 preterm infants (≤34 weeks aged 8-15 days of life, clinically stable in ambient air or oxygen catheter use. Children with heart defects, diagnosis of brain lesion and/or those using vasoactive drugs were excluded. Ultrasonographic assessments with transcranial Doppler flowmetry were performed before, during and after the increase in expiratory flow session, which lasted 5min. Cerebral blood flow velocity and resistance and pulsatility indices in the pericallosal artery were assessed. Results: Respiratory physical therapy did not significantly alter flow velocity at the systolic peak (p=0.50, the end diastolic flow velocity (p=0.17, the mean flow velocity (p=0.07, the resistance index (p=0.41 and the pulsatility index (p=0.67 over time. Conclusions: The expiratory flow increase technique did not affect cerebral blood flow in clinically-stable preterm infants.

  6. Mucosal/submucosal blood flow in the gut wall determined by local washout of 133Xenon

    DEFF Research Database (Denmark)

    Mortensen, Peter; Olsen, J; Bülow, J

    1991-01-01

    the initial slope of the washout was used for measuring blood flow rate. Blood flow rate was simultaneously measured by microsphere entrapment technique. There was an excellent correlation between the blood flow rate determined by the two techniques the correlation coefficient R being 0.89 in the small...

  7. Numerical Simulations of Blood Flows in the Left Atrium

    Science.gov (United States)

    Zhang, Lucy

    2008-11-01

    A novel numerical technique of solving complex fluid-structure interactions for biomedical applications is introduced. The method is validated through rigorous convergence and accuracy tests. In this study, the technique is specifically used to study blood flows in the left atrium, one of the four chambers in the heart. Stable solutions are obtained at physiologic Reynolds numbers by applying pulmonary venous inflow, mitral valve outflow and appropriate constitutive equations to closely mimic the behaviors of biomaterials. Atrial contraction is also implemented as a time-dependent boundary condition to realistically describe the atrial wall muscle movements, thus producing accurate interactions with the surrounding blood. From our study, the transmitral velocity, filling/emptying velocity ratio, durations and strengths of vortices are captured numerically for sinus rhythms (healthy heart beat) and they compare quite well with reported clinical studies. The solution technique can be further used to study heart diseases such as the atrial fibrillation, thrombus formation in the chamber and their corresponding effects in blood flows.

  8. Tracking flow of leukocytes in blood for drug analysis

    Science.gov (United States)

    Basharat, Arslan; Turner, Wesley; Stephens, Gillian; Badillo, Benjamin; Lumpkin, Rick; Andre, Patrick; Perera, Amitha

    2011-03-01

    Modern microscopy techniques allow imaging of circulating blood components under vascular flow conditions. The resulting video sequences provide unique insights into the behavior of blood cells within the vasculature and can be used as a method to monitor and quantitate the recruitment of inflammatory cells at sites of vascular injury/ inflammation and potentially serve as a pharmacodynamic biomarker, helping screen new therapies and individualize dose and combinations of drugs. However, manual analysis of these video sequences is intractable, requiring hours per 400 second video clip. In this paper, we present an automated technique to analyze the behavior and recruitment of human leukocytes in whole blood under physiological conditions of shear through a simple multi-channel fluorescence microscope in real-time. This technique detects and tracks the recruitment of leukocytes to a bioactive surface coated on a flow chamber. Rolling cells (cells which partially bind to the bioactive matrix) are detected counted, and have their velocity measured and graphed. The challenges here include: high cell density, appearance similarity, and low (1Hz) frame rate. Our approach performs frame differencing based motion segmentation, track initialization and online tracking of individual leukocytes.

  9. Rheology of red blood cells under flow in highly confined microchannels: I. effect of elasticity.

    Science.gov (United States)

    Lázaro, Guillermo R; Hernández-Machado, Aurora; Pagonabarraga, Ignacio

    2014-10-07

    We analyze the rheology of dilute red blood cell suspensions in pressure driven flows at low Reynolds number, in terms of the morphologies and elasticity of the cells. We focus on narrow channels of width similar to the cell diameter, when the interactions with the walls dominate the cell dynamics. The suspension presents a shear-thinning behaviour, with a Newtonian-behaviour at low shear rates, an intermediate region of strong decay of the suspension viscosity, and an asymptotic regime at high shear rates in which the effective viscosity converges to that of the solvent. We identify the relevant aspects of cell elasticity that contribute to the rheological response of blood at high confinement. In a second paper, we will explore the focusing of red blood cells while flowing at high shear rates and how this effect is controlled by the geometry of the channel.

  10. Blood pressure and blood flow variation during postural change from sitting to standing: model development and validation

    DEFF Research Database (Denmark)

    Olufsen, M.S.; Ottesen, Johnny T.; Tran, H.T.

    2005-01-01

    Short-term cardiovascular responses to postural change from sitting to standing involve complex interactions between the autonomic nervous system, which regulates blood pressure, and cerebral autoregulation, which maintains cerebral perfusion. We present a mathematical model that can predict...... dynamic changes in beat-to-beat arterial blood pressure and middle cerebral artery blood flow velocity during postural change from sitting to standing. Our cardiovascular model utilizes 11 compartments to describe blood pressure, blood flow, compliance, and resistance in the heart and systemic circulation....... To include dynamics due to the pulsatile nature of blood pressure and blood flow, resistances in the large systemic arteries are modeled using nonlinear functions of pressure. A physiologically based submodel is used to describe effects of gravity on venous blood pooling during postural change. Two types...

  11. Form, shape and function: segmented blood flow in the choriocapillaris

    Science.gov (United States)

    Zouache, M. A.; Eames, I.; Klettner, C. A.; Luthert, P. J.

    2016-10-01

    The development of fluid transport systems was a key event in the evolution of animals and plants. While within vertebrates branched geometries predominate, the choriocapillaris, which is the microvascular bed that is responsible for the maintenance of the outer retina, has evolved a planar topology. Here we examine the flow and mass transfer properties associated with this unusual geometry. We show that as a result of the form of the choriocapillaris, the blood flow is decomposed into a tessellation of functional vascular segments of various shapes delineated by separation surfaces across which there is no flow, and in the vicinity of which the transport of passive substances is diffusion-limited. The shape of each functional segment is determined by the distribution of arterioles and venules and their respective relative flow rates. We also show that, remarkably, the mass exchange with the outer retina is a function of the shape of each functional segment. In addition to introducing a novel framework in which the structure and function of the metabolite delivery system to the outer retina may be investigated in health and disease, the present work provides a general characterisation of the flow and transfers in multipole Hele-Shaw configurations.

  12. Laser Doppler flowmetry for bone blood flow measurement: correlation with microsphere estimates and evaluation of the effect of intracapsular pressure on femoral head blood flow

    Energy Technology Data Exchange (ETDEWEB)

    Swiontkowski, M.F.; Tepic, S.; Perren, S.M.; Moor, R.; Ganz, R.; Rahn, B.A.

    1986-01-01

    Laser Doppler flowmetry (LDF) was used to measure bone blood flow in the rabbit femoral condyles. To correlate the LDF output signal blood cell flux to in vivo blood flow, simultaneous measurements using LDF and /sup 85/Sr-labeled microspheres were made in an adult rabbit model. There was no correlation between the two methods for blood flow in the femoral condyles and the correlation between the two methods for blood flow in the femoral head does not achieve statistical significance. An LDF signal of 0.4 V was approximately equal to a microsphere measured flow rate of 0.4 ml blood/g bone/min. The strength of the correlation in the latter case may have been affected by (a) large arteriovenous shunts, (b) inadequate mixing of the microspheres with a left ventricular injection, and (c) insufficient numbers of microspheres present in the bone samples. When LDF was used to evaluate the effect of elevated intracapsular pressure on femoral head blood flow in skeletally mature rabbits, femoral head subchondral bone blood flow declined with increasing intracapsular pressure from a baseline value of 0.343 +/- 0.036 to a value of 0.127 +/- 0.27 at 120 cm of water pressure. The decline in femoral head blood flow was statistically significant at pressures of 40 cm of water or higher (p less than 0.001), and evaluation of sections of the proximal femora made from preterminal disulphine blue injections confirmed these findings. Intracapsular tamponade has an adverse effect on femoral head blood flow beginning well below central venous pressure and should be considered in the pathophysiology of posttraumatic and nontraumatic necrosis of the femoral head. Laser Doppler flowmetry was easy to use and appears to be a reproducible technique for evaluating femoral head blood flow, offering distinct advantages over the microsphere technique for measuring bone blood flow.

  13. Development report, mass flow controller PN 5716068

    Science.gov (United States)

    Taylor, W.

    1972-01-01

    The design, development, and manufacture of an all mechanical mass flow controller are discussed. A test program was conducted using inert gas as the test medium. The unit controlled the pressure within plus of minus one percent. An analytical method is presented for relating the control pressure error with error in mass flow.

  14. Instruction Scheduling Across Control Flow

    Directory of Open Access Journals (Sweden)

    Martin Charles Golumbic

    1993-01-01

    Full Text Available Instruction scheduling algorithms are used in compilers to reduce run-time delays for the compiled code by the reordering or transformation of program statements, usually at the intermediate language or assembly code level. Considerable research has been carried out on scheduling code within the scope of basic blocks, i.e., straight line sections of code, and very effective basic block schedulers are now included in most modern compilers and especially for pipeline processors. In previous work Golumbic and Rainis: IBM J. Res. Dev., Vol. 34, pp.93–97, 1990, we presented code replication techniques for scheduling beyond the scope of basic blocks that provide reasonable improvements of running time of the compiled code, but which still leaves room for further improvement. In this article we present a new method for scheduling beyond basic blocks called SHACOOF. This new technique takes advantage of a conventional, high quality basic block scheduler by first suppressing selected subsequences of instructions and then scheduling the modified sequence of instructions using the basic block scheduler. A candidate subsequence for suppression can be found by identifying a region of a program control flow graph, called an S-region, which has a unique entry and a unique exit and meets predetermined criteria. This enables scheduling of a sequence of instructions beyond basic block boundaries, with only minimal changes to an existing compiler, by identifying beneficial opportunities to cover delays that would otherwise have been beyond its scope.

  15. Theoretical model of blood flow measurement by diffuse correlation spectroscopy

    Science.gov (United States)

    Sakadžić, Sava; Boas, David A.; Carp, Stefan

    2017-02-01

    Diffuse correlation spectroscopy (DCS) is a noninvasive method to quantify tissue perfusion from measurements of the intensity temporal autocorrelation function of diffusely scattered light. However, DCS autocorrelation function measurements in tissue better match theoretical predictions based on the diffusive motion of the scatterers than those based on a model where the advective nature of blood flow dominates the stochastic properties of the scattered light. We have recently shown using Monte Carlo (MC) simulations and assuming a simplistic vascular geometry and laminar flow profile that the diffusive nature of the DCS autocorrelation function decay is likely a result of the shear-induced diffusion of the red blood cells. Here, we provide theoretical derivations supporting and generalizing the previous MC results. Based on the theory of diffusing-wave spectroscopy, we derive an expression for the autocorrelation function along the photon path through a vessel that takes into account both diffusive and advective scatterer motion, and we provide the solution for the DCS autocorrelation function in a semi-infinite geometry. We also derive the correlation diffusion and correlation transfer equation, which can be applied for an arbitrary sample geometry. Further, we propose a method to take into account realistic vascular morphology and flow profile.

  16. Autoregulation of cerebral blood flow in orthostatic hypotension

    Science.gov (United States)

    Novak, V.; Novak, P.; Spies, J. M.; Low, P. A.

    1998-01-01

    BACKGROUND AND PURPOSE: We sought to evaluate cerebral autoregulation in patients with orthostatic hypotension (OH). METHODS: We studied 21 patients (aged 52 to 78 years) with neurogenic OH during 80 degrees head-up tilt. Blood flow velocities (BFV) from the middle cerebral artery were continuously monitored with transcranial Doppler sonography, as were heart rate, blood pressure (BP), cardiac output, stroke volume, CO2, total peripheral resistance, and cerebrovascular resistance. RESULTS: All OH patients had lower BP (PTPR (P.75) but with a flat slope. An expansion of the "autoregulated" range was seen in some patients. The OH_AF group was characterized by a profound fall in BFV in response to a small reduction in BP (mean deltaBP .75). CONCLUSIONS: The most common patterns of cerebral response to OH are autoregulatory failure with a flat flow-pressure relationship or intact autoregulation with an expanded autoregulated range. The least common pattern is autoregulatory failure with a steep flow-pressure relationship. Patients with patterns 1 and 2 have an enhanced capacity to cope with OH, while those with pattern 3 have reduced capacity.

  17. Computer-controlled positive displacement pump for physiological flow simulation.

    Science.gov (United States)

    Holdsworth, D W; Rickey, D W; Drangova, M; Miller, D J; Fenster, A

    1991-11-01

    A computer-controlled pump for use both in the study of vascular haemodynamics and in the calibration of clinical devices which measure blood flow is designed. The novel design of this pump incorporates two rack-mounted pistons, driven into opposing cylinders by a micro-stepping motor. This approach allows the production of nearly uninterrupted steady flow, as well as a variety of pulsatile waveforms, including waveforms with reverse flow. The capabilities of this pump to produce steady flow from 0.1 to 60 ml s-1, as well as sinusoidal flow and physiological flow, such as that found in the common femoral and common carotid arteries are demonstrated. Cycle-to-cycle reproducibility is very good, with an average variation of 0.1 ml s-1 over thousands of cycles.

  18. Regional cerebral blood flow and blood volume in patients with subcortical arteriosclerotic encephalopathy (SAE).

    Science.gov (United States)

    Gückel, Friedemann J; Brix, Gunnar; Hennerici, Michael; Lucht, Robert; Ueltzhöffer, Christine; Neff, Wolfgang

    2007-10-01

    The aim of the present study was a detailed analysis of the regional cerebral blood flow and blood volume in patients with subcortical arteriosclerotic encephalopathy (SAE) by means of functional magnetic resonance imaging (MRI). A group of 26 patients with SAE and a group of 16 age-matched healthy volunteers were examined. Using a well-established dynamic susceptibility contrast-enhanced MRI method, the regional cerebral blood flow (rCBF) and blood volume (rCBV) were quantified for each subject in 12 different regions in the brain parenchyma. As compared to healthy volunteers, patients with SAE showed significantly reduced rCBF and rCBV values in white matter regions and in the occipital cortex. Regions containing predominantly grey matter show almost normal rCBF and rCBV values. In conclusion, quantitative analysis of rCBF and rCBV values demonstrates clearly that SAE is a disease that is associated with a reduced microcirculation predominantly in white matter.

  19. Measurement of utero-placental blood flow with /sup 113m/In in diabetic pregnancy

    Energy Technology Data Exchange (ETDEWEB)

    Semmler, K.; Kirsch, G.; Zoellner, P.; Fuhrmann, K.; Jutzi, E. (Zentralinstitut fuer Diabetes, Karlsburg (German Democratic Republic); Ernst-Moritz-Arndt-Universitaet, Greifswald (German Democratic Republic). Radiologische Klinik)

    1985-01-01

    In 122 diabetic pregnancies the placental blood flow has been estimated determining the half-life of the activity inflow (2 MBq /sup 113m/In-transferrin) into the placenta. A highly sensitive detector (modified pinhole collimator) and a computer-supported evaluation were used. 259 flow measurements were compared to the risk of complication in the course of diabetic pregnancy. The half-life values in the diabetic group, calculated by a gamma camera computer system by means of an iterative regression analysis, were significantly different compared to a control group (12 pregnancies without risk.) Severe diabetic angiopathic complications (classes D, F, and R according to White) are accompanied by higher half-life values (placental blood flow reductions) and perinatal complications. Even in pregnant women with gestational diabetes of disturbances of the carbohydrate metabolism disturbed placental hemodynamics is to be found.

  20. Instability of the middle cerebral artery blood flow in response to CO2.

    Directory of Open Access Journals (Sweden)

    Rosemary E Regan

    Full Text Available BACKGROUND: The middle cerebral artery supplies long end-artery branches to perfuse the deep white matter and shorter peripheral branches to perfuse cortical and subcortical tissues. A generalized vasodilatory stimulus such as carbon dioxide not only results in an increase in flow to these various tissue beds but also redistribution among them. We employed a fast step increase in carbon dioxide to detect the dynamics of the cerebral blood flow response. METHODOLOGY/PRINCIPAL FINDINGS: The study was approved by the Research Ethics Board of the University Health Network at the University of Toronto. We used transcranial ultrasound to measure the time course of middle cerebral artery blood flow velocity in 28 healthy adults. Normoxic, isoxic step increases in arterial carbon dioxide tension of 10 mmHg from both hypocapnic and normocapnic baselines were produced using a new prospective targeting system that enabled a more rapid step change than has been previously achievable. In most of the 28 subjects the responses at both carbon dioxide ranges were characterised by more complex responses than a single exponential rise. Most responses were characterised by a fast initial response which then declined rapidly to a nadir, followed by a slower secondary response, with some showing oscillations before stabilising. CONCLUSIONS/SIGNIFICANCE: A rapid step increase in carbon dioxide tension is capable of inducing instability in the cerebral blood flow control system. These dynamic aspects of the cerebral blood flow responses to rapid changes in carbon dioxide must be taken into account when using transcranial blood flow velocity in a single artery segment to measure cerebrovascular reactivity.

  1. Cerebral blood flow autoregulation in experimental liver failure

    DEFF Research Database (Denmark)

    Dethloff, T.J.; Larsen, F.S.; Knudsen, Gitte Moos

    2008-01-01

    Patients with acute liver failure (ALF) display impairment of cerebral blood flow (CBF) autoregulation, which may contribute to the development of fatal intracranial hypertension, but the pathophysiological mechanism remains unclear. In this study, we examined whether loss of liver mass causes...... impairment of CBF autoregulation. Four rat models were chosen, each representing different aspects of ALF: galactosamine (GlN) intoxication represented liver necrosis, 90% hepatectomy (PHx90) represented reduction in liver mass, portacaval anastomosis (PCA) represented shunting of blood....../toxins into the systemic circulation thus mimicking intrahepatic shunting in ALF, PCA+NH(3) provided information about the additional effects of hyperammonemia Rats were intubated and sedated with pentobarbital. We measured CBF with laser Doppler, intracranial pressure (ICP) was measured in the fossa posterior...

  2. Noninvasive deadbeat control of an implantable rotary blood pump: a simulation study.

    Science.gov (United States)

    Lim, E; Alomari, A H; Savkin, A V; Lovell, N H

    2009-01-01

    A deadbeat controller has been proposed for the control of pulsatile pump flow in an implantable rotary blood pump (IRBP). A lumped parameter model of the cardiovascular system, in combination with the stable dynamical models of pulsatile flow and differential pressure (head) estimation for the IRBP was used to evaluate the controller. Pump speed and current were used as the only measured variables of the control system. The control algorithm was tested using both constant and sinusoidal reference pump flow input, under healthy and heart failure conditions. Results showed that the controller is able to track the reference input with minimal error in the presence of model uncertainty.

  3. Carbon dioxide induced changes in cerebral blood flow and flow velocity: role of cerebrovascular resistance and effective cerebral perfusion pressure.

    Science.gov (United States)

    Grüne, Frank; Kazmaier, Stephan; Stolker, Robert J; Visser, Gerhard H; Weyland, Andreas

    2015-09-01

    In addition to cerebrovascular resistance (CVR) zero flow pressure (ZFP), effective cerebral perfusion pressure (CPPe) and the resistance area product (RAP) are supplemental determinants of cerebral blood flow (CBF). Until now, the interrelationship of PaCO2-induced changes in CBF, CVR, CPPe, ZFP, and RAP is not fully understood. In a controlled crossover trial, we investigated 10 anesthetized patients aiming at PaCO2 levels of 30, 37, 43, and 50 mm Hg. Cerebral blood flow was measured with a modified Kety-Schmidt-technique. Zero flow pressure and RAP was estimated by linear regression analysis of pressure-flow velocity relationships of the middle cerebral artery. Effective cerebral perfusion pressure was calculated as the difference between mean arterial pressure and ZFP, CVR as the ratio CPPe/CBF. Statistical analysis was performed by one-way RM-ANOVA. When comparing hypocapnia with hypercapnia, CBF showed a significant exponential reduction by 55% and mean VMCA by 41%. Effective cerebral perfusion pressure linearly decreased by 17% while ZFP increased from 14 to 29 mm Hg. Cerebrovascular resistance increased by 96% and RAP by 39%; despite these concordant changes in mean CVR and Doppler-derived RAP correlation between these variables was weak (r=0.43). In conclusion, under general anesthesia hypocapnia-induced reduction in CBF is caused by both an increase in CVR and a decrease in CPPe, as a consequence of an increase in ZFP.

  4. Endoscopic retrograde cholangiopancreatography causes reduced myocardial blood flow

    DEFF Research Database (Denmark)

    Christensen, M; Hendel, H W; Rasmussen, V;

    2002-01-01

    ). PATIENTS AND METHODS: 11 patients scheduled for ERCP were monitored with a Holter tape recorder and underwent myocardial perfusion scintigraphies, to evaluate myocardial perfusion at rest and during ERCP. RESULTS: Ten patients completed the study. Eight patients had no sign of myocardial ischemia...... with either of the two methods, while two patients developed signs of ischemia during ERCP with both the Holter tape recording and on myocardial scintigraphy (P = 0.02). CONCLUSIONS: Patients undergoing ERCP may develop true myocardial ischemia with reduced myocardial blood flow. Although this is a small...

  5. Skin blood flow with elastic compressive extravehicular activity space suit.

    Science.gov (United States)

    Tanaka, Kunihiko; Gotoh, Taro M; Morita, Hironobu; Hargens, Alan R

    2003-10-01

    During extravehicular activity (EVA), current space suits are pressurized with 100% oxygen at approximately 222 mmHg. A tight elastic garment, or mechanical counter pressure (MCP) suit that generates pressure by compression, may have several advantages over current space suit technology. In this study, we investigated local microcirculatory effects produced with negative ambient pressure with an MCP sleeve. The MCP glove and sleeve generated pressures similar to the current space suit. MCP remained constant during negative pressure due to unchanged elasticity of the material. Decreased skin capillary blood flow and temperature during MCP compression was counteracted by greater negative pressure or a smaller pressure differential.

  6. Dynamics of renal blood flow autoregulation in rats

    DEFF Research Database (Denmark)

    Holstein-Rathlou, N H; Wagner, A J; Marsh, D J

    1991-01-01

    Two separate components could be resolved in tests of the dynamic autoregulation of renal blood flow. The slow component corresponds to the frequency at which spontaneous proximal tubular pressure oscillations are found, and are most likely due to the operation of the TGF. The high frequency...... component most likely represents an intrinsic vascular, myogenic, mechanism. The gain maximum of the admittance in the frequency range corresponding to the autonomous tubular oscillations indicates that the dynamic characteristics responsible for the occurrence of the spontaneous tubular oscillations must...

  7. Developmental validation of a novel lateral flow strip test for rapid identification of human blood (Rapid Stain Identification--Blood).

    Science.gov (United States)

    Schweers, Brett A; Old, Jennifer; Boonlayangoor, P W; Reich, Karl A

    2008-06-01

    Human blood is the body fluid most commonly encountered at crime scenes, and blood detection may aid investigators in reconstructing what occurred during a crime. In addition, blood detection can help determine which items of evidence should be processed for DNA-STR testing. Unfortunately, many common substances can cause red-brown stains that resemble blood. Furthermore, many current human blood detection methods are presumptive and prone to false positive results. Here, the developmental validation of a new blood identification test, Rapid Stain Identification--Blood (RSID--Blood), is described. RSID--Blood utilizes two anti-glycophorin A (red blood cell membrane specific protein) monoclonal antibodies in a lateral flow strip test format to detect human blood. We present evidence demonstrating that this test is accurate, reproducible, easy to use, and highly specific for human blood. Importantly, RSID--Blood does not cross-react with ferret, skunk, or primate blood and exhibits no high-dose hook effect. Also, we describe studies on the sensitivity, body fluid specificity, and species specificity of RSID--Blood. In addition, we show that the test can detect blood from a variety of forensic exhibits prior to processing for DNA-STR analysis. In conclusion, we suggest that RSID--Blood is effective and useful for the detection of human blood on forensic exhibits, and offers improved blood detection when compared to other currently used methods.

  8. Ultrasonic characteristics and clinical significance of umbilical cord blood flow in acute fetal distress

    Institute of Scientific and Technical Information of China (English)

    Wei Dai; Yin Xu; Xing-Wei Ma; Li Zhang; Ming-Juan Zhu

    2016-01-01

    Objective: To study ultrasonic characteristics of umbilical cord blood flow in acute fetal distress and its correlation with umbilical artery blood gas parameters, oxidative stress parameters, neonatal brain injury and myocardial injury. Methods: The pregnant women delivered in Department of Obstetrics of our hospital were chosen during the period from May 2012 to August 2015. The pregnant women with acute fetal distress were included in the distress group, and the healthy pregnant women with no acute fetal distress were included in the control group. The resistance index (RI), pulsatility index (PI) and systolic/diastolic (S/D) ratio of umbilical artery were measured at 24–30 weeks, 31–36 weeks and 37–41 weeks of pregnancy. After delivery, umbilical artery blood was taken for analysis of blood gas and determination of oxidative stress parameters. The venous blood of newborns was taken to measure the myocardial injury and brain injury parameters. Results: At 24–30 weeks, 31–36 weeks and 37–41 weeks of pregnancy, RI, S/D and PI in pregnant women of distress group were significantly higher than those in control group. The pH, contents of arterial partial pressure of oxygen, vitamin C, vitamin E, superoxide dis-mutase and glutathione peroxidase in umbilical artery blood in pregnant women of distress group was significantly lower than those in control group and negatively correlated with the umbilical artery RI, PI and S/D. The contents of partial pressure of carbon dioxide in artery, lactic acid and malondialdehyde in pregnant women of distress group were significantly higher than those in control group and positively correlated with the umbilical artery RI, PI and S/D. The contents of lactate dehydrogenase, hydroxybutyrate dehydrogenase, creatine kinase, creatine kinase-MB, S100B, neuron-specific enolase, creatine kinase-BB and Tau in newborns' venous blood in distress group were significantly higher than those in control group and positively correlated

  9. Ultrasonic character istics and clinical significance of umbilical cord blood flow in acute fetal distress

    Directory of Open Access Journals (Sweden)

    Wei Dai, Yin Xu

    2016-11-01

    Full Text Available Objective: To study ultrasonic characteristics of umbilical cord blood flow in acute fetal distress and its correlation with umbilical artery blood gas parameters, oxidative stress parameters, neonatal brain injury and myocardial injury. Methods: The pregnant women delivered in Department of Obstetrics of our hospital were chosen during the period from May 2012 to August 2015. The pregnant women with acute fetal distress were included in the distress group, and the healthy pregnant women with no acute fetal distress were included in the control group. The resistance index (RI, pulsatility index (PI and systolic/diastolic (S/D ratio of umbilical artery were measured at 24–30 weeks, 31–36 weeks and 37–41 weeks of pregnancy. After delivery, umbilical artery blood was taken for analysis of blood gas and determination of oxidative stress parameters. The venous blood of newborns was taken to measure the myocardial injury and brain injury parameters. Results: At 24–30 weeks, 31–36 weeks and 37–41 weeks of pregnancy, RI, S/D and PI in pregnant women of distress group were significantly higher than those in control group. The pH, contents of arterial partial pressure of oxygen, vitamin C, vitamin E, superoxide dismutase and glutathione peroxidase in umbilical artery blood in pregnant women of distress group was significantly lower than those in control group and negatively correlated with the umbilical artery RI, PI and S/D. The contents of partial pressure of carbon dioxide in artery, lactic acid and malondialdehyde in pregnant women of distress group were significantly higher than those in control group and positively correlated with the umbilical artery RI, PI and S/D. The contents of lactate dehydrogenase, hydroxybutyrate dehydrogenase, creatine kinase, creatine kinase-MB, S100B, neuron-specific enolase, creatine kinase-BB and Tau in newborns' venous blood in distress group were significantly higher than those in control group and

  10. In-vitro laser anemometry blood flow systems

    Science.gov (United States)

    Liepsch, Dieter W.; Poll, Axel; Pflugbeil, Gottlieb

    1993-08-01

    Lasers are used in a wide variety of medical applications. While laser catheters have been developed for highly accurate velocity measurements these are invasive; noninvasive techniques are more desirable but not as precise. The laser is, however, a great tool for in vitro measurements. Several groups internationally are using the laser in the study of local velocity distribution in microscopic areas of specially constructed models. Laser Doppler anemometry is widely used to measure the local, time-dependent velocities, while phase Doppler anemometry has been developed to measure particle size, distribution and velocity. Most recently, laser analyzer techniques have been developed for analyzing the particle size of two phase flow systems. It has become increasingly important for physicians to visualize blood flow. In addition to the techniques mentioned above, several laser sheet techniques have been developed for precise measurements. This paper presents a short review of laser techniques and shows some applications especially for the laser-Doppler anemometer.

  11. Holographic laser Doppler imaging of microvascular blood flow

    CERN Document Server

    Magnain, C; Boucneau, T; Simonutti, M; Ferezou, I; Rancillac, A; Vitalis, T; Sahel, J A; Paques, M; Atlan, M

    2014-01-01

    We report on local superficial blood flow monitoring in biological tissue from laser Doppler holographic imaging. In time averaging recording conditions, holography acts as a narrowband bandpass filter, which, combined with a frequency shifted reference beam, permits frequency selective imaging in the radiofrequency range. These Doppler images are acquired with an off axis Mach Zehnder interferometer. Microvascular hemodynamic components mapping is performed in the cerebral cortex of the mouse and the eye fundus of the rat with near-infrared laser light without any exogenous marker. These measures are made from a basic inverse method analysis of local first order optical fluctuation spectra at low radiofrequencies, from 0 Hz to 100 kHz. Local quadratic velocity is derived from Doppler broadenings induced by fluid flows, with elementary diffusing wave spectroscopy formalism in backscattering configuration. We demonstrate quadratic mean velocity assessment in the 0.1 to 10 millimeters per second range in vitro ...

  12. Cerebral blood flow in patients with dementia of Alzheimer's type

    DEFF Research Database (Denmark)

    Postiglione, A; Lassen, N A; Holman, B L

    1993-01-01

    In the normal brain as well as in Alzheimer's disease (AD), regional cerebral blood flow (CBF) is coupled to metabolic demand and, therefore, changes in CBF reflect variations in neuronal metabolism. The use of radionuclide techniques, such as positron emission tomography (PET) and single photon...... of the disease. Lateral CBF asymmetry is also very frequent; speech disorders are highly characteristic of left-sided flow reduction, while visuospatial apraxia is dominating in the right-sided cases. In advanced and severe cases of AD, CBF and metabolism tend to be more uniformly reduced throughout the cortex......, sparing only the primary visual and sensory-motor cortices. PET and SPECT measurement of brain perfusion and metabolism has added a new dimension to the knowledge of dementia disorders, with a better differential diagnosis between AD and other forms of dementia. The correlation with neuropsychological...

  13. Validation of Blood Flow Simulations in Intracranial Aneurysms

    Science.gov (United States)

    Yu, Yue; Anor, Tomer; Baek, Hyoungsu; Jayaraman, Mahesh; Madsen, Joseph; Karniadakis, George

    2010-11-01

    Catheter-based digital subtraction angiography (DSA) is the most accurate diagnostic procedure for investigating vascular anomalies and cerebral blood flow. Here we describe utilization of DSA in a patient with an intracranial aneursysm to validate corresponding spectral element simulations. Subsequently, we examine via visualization the structure of flow in internal carotid arteries laden with three different types of aneurysms: (1) a wide-necked saccular aneurysm, (2) a narrower-necked saccular aneurysm, and (3) a case with two adjacent saccular aneurysms. We have found through high resolution simulations that in cases (1) and (3) in physiological conditions a hydrodynamic instability occurs during the decelerating systolic phase resulting in a high frequency oscillation (20-50 Hz). We use the in-silico dye visualization to discriminate among different physical mechanisms causing the instability and contrast their effect with case (2) for which an instability arises only at much higher flowrates.

  14. Twenty-four hour blood flow in the forefoot after reconstructive vascular surgery

    Energy Technology Data Exchange (ETDEWEB)

    Jelnes, R.

    1986-08-01

    Local blood flow in the forefoot (SBF) was measured continuously during 24 hours by 133xenon clearance technique in 10 patients prior to and at least 1 year after successful reconstructive vascular surgery for severe arterial insufficiency (mean: 18 months, range: 12-36). A group of 10 patients with normal peripheral circulation served as a control group. In spite of a considerable increase of the ankle/arm systolic blood pressure index--preoperative: 0.30 +/- 0.12, postoperative: 0.78 +/- 0.28 (mean +/- 1 SD)--the SBF decreased by 50% (p less than 0.001) following reconstructive vascular surgery during day activities. During sleep, however, SBF increased by 80% (p less than 0.001). The relative changes in SBF from day to night at the postoperative examination did not differ from that of the control group, i.e., the normal 24-hour blood flow pattern had been obtained. These changes in SBF are explained by the reappearance of peripheral vasoregulatory mechanisms. Postreconstructive hyperemia was evaluated by the same technique. The changes in SBF following surgery in the positions supine, awake and supine, asleep were found to be insignificant (0.80 less than p less than 0.90). It is concluded that the long-term postreconstructive hyperemia merely is a reflection of the normal 24-hour blood flow pattern.

  15. Doppler sonography of diabetic feet: Quantitative analysis of blood flow volume

    Energy Technology Data Exchange (ETDEWEB)

    Seo, Young Lan; Kim, Ho Chul; Choi, Chul Soon; Yoon, Dae Young; Han, Dae Hee; Moon, Jeung Hee; Bae, Sang Hoon [Hallym University College of Medicine, Seoul (Korea, Republic of)

    2002-09-15

    To analyze Doppler sonographic findings of diabetic feet by estimating the quantitative blood flow volume and by analyzing waveform on Doppler. Doppler sonography was performed in thirty four patients (10 diabetic patients with foot ulceration, 14 diabetic patients without ulceration and 10 normal patients as the normal control group) to measure the flow volume of the arteries of the lower extremities (posterior and anterior tibial arteries, and distal femoral artery. Analysis of doppler waveforms was also done to evaluate the nature of the changed blood flow volume of diabetic patients, and the waveforms were classified into triphasic, biphasic-1, biphasic-2 and monophasic patterns. Flow volume of arteries in diabetic patients with foot ulceration was increased witha statistical significance when compared to that of diabetes patients without foot ulceration of that of normal control group (P<0.05). Analysis of Doppler waveform revealed that the frequency of biphasic-2 pattern was significantly higher in diabetic patients than in normal control group(p<0.05). Doppler sonography in diabetic feet showed increased flow volume and biphasic Doppler waveform, and these findings suggest neuropathy rather than ischemic changes in diabetic feet.

  16. Numerical Simulation of Unsteady Blood Flow through Capillary Networks.

    Science.gov (United States)

    Davis, J M; Pozrikidis, C

    2011-08-01

    A numerical method is implemented for computing unsteady blood flow through a branching capillary network. The evolution of the discharge hematocrit along each capillary segment is computed by integrating in time a one-dimensional convection equation using a finite-difference method. The convection velocity is determined by the local and instantaneous effective capillary blood viscosity, while the tube to discharge hematocrit ratio is deduced from available correlations. Boundary conditions for the discharge hematocrit at divergent bifurcations arise from the partitioning law proposed by Klitzman and Johnson involving a dimensionless exponent, q≥1. When q=1, the cells are partitioned in proportion to the flow rate; as q tends to infinity, the cells are channeled into the branch with the highest flow rate. Simulations are performed for a tree-like, perfectly symmetric or randomly perturbed capillary network with m generations. When the tree involves more than a few generations, a supercritical Hopf bifurcation occurs at a critical value of q, yielding spontaneous self-sustained oscillations in the absence of external forcing. A phase diagram in the m-q plane is presented to establish conditions for unsteady flow, and the effect of various geometrical and physical parameters is examined. For a given network tree order, m, oscillations can be induced for a sufficiently high value of q by increasing the apparent intrinsic viscosity, decreasing the ratio of the vessel diameter from one generation to the next, or by decreasing the diameter of the terminal vessels. With other parameters fixed, oscillations are inhibited by increasing m. The results of the continuum model are in excellent agreement with the predictions of a discrete model where the motion of individual cells is followed from inlet to outlet.

  17. The Noninvasive Measurement Research of Human Blood Parameters under Flow Control of Time Gate%血流控制下时间门的人体血液参数无创检测研究

    Institute of Scientific and Technical Information of China (English)

    吴金鹏; 孙美秀; 康美玲; 李刚; 李迎新

    2013-01-01

    为了进一步提高人体血液成分无创伤测量的精度,从而达到临床的要求,提出了人体血液成分无创伤测量的一种新方法,这种方法是在血流受阻条件下,基于动力双波长时间分辨透射测量,将先进的时间门技术和拉普拉斯变换方法结合起来,对人体血液成分进行无创伤测量.该理论模拟了利用该方法在体测量人体血液参数,模拟结果显示当p>0,强调早期到达的光子的贡献时,能提高人体血液参数的检测灵敏度.%In order to further improve the noninvasive measurement precision of human blood components and achieve clinical requirements,we propose a new measurement method based on the dynamic dual wavelength time-resolved transmittance measurement,combined with the advanced time gate technology and Laplasse transform to detect human blood components noninvasively in the blocked blood flow conditions.Simulation results show that when p>O,emphasizing the importance of early arriving photons contribution can enhance the detection sensitivity of human body blood parameters.

  18. [Digital blood flow measurement by venous occlusion plethysmography in Raynaud's phenomenon. Value of the rewarming test].

    Science.gov (United States)

    Cristol, R; Debray, J

    1986-01-01

    The fingertip blood flow measured by mercury strain gauge plethysmography with venous occlusion, at 22 degrees C room temperature, had significantly lower mean values in 190 patients with Raynaud's phenomenon (55 men aged 49 yrs +/- 16, 135 women aged 48 yrs +/- 16) than in 40 age and sex matched controls: 18 ml/100 ml/minute +/- 14.6 versus 35 ml/100 ml/minute +/- 15 at level p less than 0.01. The mean fingertip blood flow was significantly lower (p less than 0.01) in 31 cases of scleroderma and 32 cases of pulpar necrosis (respectively 13 ml +/- 13 and 11 ml +/- 8) than in 55 cases of primary Raynaud's disease (no detectable etiology and normal capillaroscopy 5 years after onset) or in 34 cases of mild Raynaud's phenomenon (respectively 21.6 +/- 16 and 24.4 +/- 18). A warming test (both hands in water at 45 degrees C during 3 minutes) was performed in 50 cases with low basal fingertip blood flow. It induced a "normalized" flow in 22 cases (mostly primary or mild Raynaud), a partly improved flow in 20 cases (mostly secondary Raynaud) and no improvement in 8 cases (scleroderma). The warming test appears to be clinically useful to assess the vasospasm and the vasodilating capabilities.

  19. Human red blood cells deformed under thermal fluid flow.

    Science.gov (United States)

    Foo, Ji-Jinn; Chan, Vincent; Feng, Zhi-Qin; Liu, Kuo-Kang

    2006-03-01

    The flow-induced mechanical deformation of a human red blood cell (RBC) during thermal transition between room temperature and 42.0 degrees C is interrogated by laser tweezer experiments. Based on the experimental geometry of the deformed RBC, the surface stresses are determined with the aid of computational fluid dynamics simulation. It is found that the RBC is more deformable while heating through 37.0 degrees C to 42.0 degrees C, especially at a higher flow velocity due to a thermal-fluid effect. More importantly, the degree of RBC deformation is irreversible and becomes softer, and finally reaches a plateau (at a uniform flow velocity U > 60 microm s(-1)) after the heat treatment, which is similar to a strain-hardening dominated process. In addition, computational simulated stress is found to be dependent on the progression of thermotropic phase transition. Overall, the current study provides new insights into the highly coupled temperature and hydrodynamic effects on the biomechanical properties of human erythrocyte in a model hydrodynamic flow system.

  20. Measurement of anterior and posterior circulation flow contributions to cerebral blood flow. An ultrasound-derived volumetric flow analysis.

    Science.gov (United States)

    Boyajian, R A; Schwend, R B; Wolfe, M M; Bickerton, R E; Otis, S M

    1995-01-01

    Ultrasound-derived volumetric flow analysis may be useful in answering questions of basic physiological interest in the cerebrovascular circulation. Using this technique, the authors have sought to describe quantitatively the complete concurrent flow relations among all four arteries supplying the brain. The aim of this study of normal subjects was to determine the relative flow contributions of the anterior (internal carotid arteries) and posterior (vertebral arteries) cerebral circulation. Comparisons between the observed and theoretically expected anterior and posterior flow distribution would provide an opportunity to assess traditional rheological conceptions in vivo. Pulsed color Doppler ultrasonography was used to measure mean flow rates in the internal carotid and vertebral arteries in 21 normal adults. The anterior circulation (internal carotid arteries bilaterally) carried 82% of the brain's blood supply and comprised 67% of the total vascular cross-sectional area. These values demonstrate precise concordance between observations in vivo and the theoretically derived (Hagen-Poiseuille) expected flow distribution. These cerebrovascular findings support the traditional conception of macroscopic blood flow. Further studies using ultrasound-derived volumetric analysis of the brain's arterial flow relations may illuminate the vascular pathophysiology underlying aging, cerebral ischemia, and dementias.

  1. Treatment of Chronic Renal Failure by Supplementing the Kidney and Invigorating Blood Flow

    Institute of Scientific and Technical Information of China (English)

    张勉之; 张大宁; 张文柱; 刘树松; 张敏英

    2004-01-01

    Objective: To evaluate the effectiveness of treatment of chronic renal failure by supplementing the kidney and invigorating blood flow. Method: The eligible patients were assigned to a treatment group (N =120)treated with the above principle and a control group (N = 128) treated with western drugs, and the effectiveness was evaluated when the study was completed in one year. Results: The total effective rate of 92.5% was achieved in the treatment group, better than that in the control group (49.2%); the difference was significant (P<0.01), especially in patients of stage Ⅰ and Ⅱ. Conclusion: The treatment of chronic renal failure by supplementing the kidney and invigorating blood flow proved to be very effective.

  2. A reconstruction method of intra-ventricular blood flow using color flow ultrasound: a simulation study

    Science.gov (United States)

    Jang, Jaeseong; Ahn, Chi Young; Jeon, Kiwan; Choi, Jung-il; Lee, Changhoon; Seo, Jin Keun

    2015-03-01

    A reconstruction method is proposed here to quantify the distribution of blood flow velocity fields inside the left ventricle from color Doppler echocardiography measurement. From 3D incompressible Navier- Stokes equation, a 2D incompressible Navier-Stokes equation with a mass source term is derived to utilize the measurable color flow ultrasound data in a plane along with the moving boundary condition. The proposed model reflects out-of-plane blood flows on the imaging plane through the mass source term. For demonstrating a feasibility of the proposed method, we have performed numerical simulations of the forward problem and numerical analysis of the reconstruction method. First, we construct a 3D moving LV region having a specific stroke volume. To obtain synthetic intra-ventricular flows, we performed a numerical simulation of the forward problem of Navier-Stokes equation inside the 3D moving LV, computed 3D intra-ventricular velocity fields as a solution of the forward problem, projected the 3D velocity fields on the imaging plane and took the inner product of the 2D velocity fields on the imaging plane and scanline directional velocity fields for synthetic scanline directional projected velocity at each position. The proposed method utilized the 2D synthetic projected velocity data for reconstructing LV blood flow. By computing the difference between synthetic flow and reconstructed flow fields, we obtained the averaged point-wise errors of 0.06 m/s and 0.02 m/s for u- and v-components, respectively.

  3. Plasma Control of Turbine Secondary Flows Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose Phase I and II efforts that will focus on turbomachinery flow control. Specifically, the present work will investigate active control in a high speed...

  4. The influence of venous blood flow on the retinal ganglion cell complex in patients with primary open angle glaucoma

    Directory of Open Access Journals (Sweden)

    N. I. Kurysheva

    2014-07-01

    Full Text Available Purpose: To study the influence of venous blood flow on the ganglion cell complex (GCC in patients with preperimetric and perimetric open angle glaucoma.Methods: 74 patients were included in the research. 59 eyes and 62 eyes were diagnosed with preperimetric and perimetric open angle glaucoma respectively. The mean age was 56.5±10.5 years. 22 (12 female and 10 male healthy individuals constituted the control group. The ganglion cell complex and retinal nerve fibre layer were evaluated with the help of optical coherence tomography (RTVue-100 OCT, Optovue, Inc., Fremont, CA. Ocular blood flow was measured by Color Doppler Imaging (multifunctional VOLUSON 730 ProSystem. The statistical analysis included correlation between GCC and RNFL thickness in both glaucoma groups.Results: The results showed a statistically significant reduction of venous blood flow velocity in both glaucoma groups compared to the control group. No difference in venous blood flow parameters between two glaucoma groups was found, except resistance index, which was higher in perimetric group in comparison to preperimetric group. A correlation was also obtained between venous blood flow parameters and GCC and RNFL thickness in both glaucoma groups.Conclusion: Early GCC damage in glaucoma might occur due to venous blood flow reduction. This fact may be of great value in understanding glaucoma pathogenesis and search for novel treatment options.

  5. Monitoring blood flow and photobleaching during topical ALA PDT treatment

    Science.gov (United States)

    Sands, Theresa L.; Sunar, Ulas; Foster, Thomas H.; Oseroff, Allan R.

    2009-02-01

    Photodynamic therapy (PDT) using topical aminolevulinic acid (ALA) is currently used as a clinical treatment for nonmelanoma skin cancers. In order to optimize PDT treatment, vascular shutdown early in treatment must be identified and prevented. This is especially important for topical ALA PDT where vascular shutdown is only temporary and is not a primary method of cell death. Shutdown in vasculature would limit the delivery of oxygen which is necessary for effective PDT treatment. Diffuse correlation spectroscopy (DCS) was used to monitor relative blood flow changes in Balb/C mice undergoing PDT at fluence rates of 10mW/cm2 and 75mW/cm2 for colon-26 tumors implanted intradermally. DCS is a preferable method to monitor the blood flow during PDT of lesions due to its ability to be used noninvasively throughout treatment, returning data from differing depths of tissue. Photobleaching of the photosensitizer was also monitored during treatment as an indirect manner of monitoring singlet oxygen production. In this paper, we show the conditions that cause vascular shutdown in our tumor model and its effects on the photobleaching rate.

  6. Multiscale modeling and simulation of brain blood flow

    Energy Technology Data Exchange (ETDEWEB)

    Perdikaris, Paris, E-mail: parisp@mit.edu [Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Grinberg, Leopold, E-mail: leopoldgrinberg@us.ibm.com [IBM T.J Watson Research Center, 1 Rogers St, Cambridge, Massachusetts 02142 (United States); Karniadakis, George Em, E-mail: george-karniadakis@brown.edu [Division of Applied Mathematics, Brown University, Providence, Rhode Island 02912 (United States)

    2016-02-15

    The aim of this work is to present an overview of recent advances in multi-scale modeling of brain blood flow. In particular, we present some approaches that enable the in silico study of multi-scale and multi-physics phenomena in the cerebral vasculature. We discuss the formulation of continuum and atomistic modeling approaches, present a consistent framework for their concurrent coupling, and list some of the challenges that one needs to overcome in achieving a seamless and scalable integration of heterogeneous numerical solvers. The effectiveness of the proposed framework is demonstrated in a realistic case involving modeling the thrombus formation process taking place on the wall of a patient-specific cerebral aneurysm. This highlights the ability of multi-scale algorithms to resolve important biophysical processes that span several spatial and temporal scales, potentially yielding new insight into the key aspects of brain blood flow in health and disease. Finally, we discuss open questions in multi-scale modeling and emerging topics of future research.

  7. Clustering of microscopic particles in constricted blood flow

    CERN Document Server

    Bächer, Christian; Gekle, Stephan

    2016-01-01

    A mixed suspension of red blood cells (RBCs) and microparticles flows through a cylindrical channel with a constriction mimicking a stenosed blood vessel. Our three-dimensional Lattice-Boltzmann simulations show that the RBCs are depleted right ahead and after the constriction. Although the RBC mean concentration (hematocrit) is 16.5% or 23.7%, their axial concentration profile is very similar to that of isolated tracer particles flowing along the central axis. Most importantly, however, we find that the stiff microparticles exhibit the opposite behavior. Arriving on a marginated position near the channel wall, they can pass through the constriction only if they find a suitable gap to dip into the dense plug of RBCs occupying the channel center. This leads to a prolonged dwell time and, as a consequence, to a pronounced increase in microparticle concentration right in front of the constriction. For biochemically active particles such as drug delivery agents or activated platelets this clustering may lead to p...

  8. Clustering of microscopic particles in constricted blood flow

    Science.gov (United States)

    Bächer, Christian; Schrack, Lukas; Gekle, Stephan

    2017-01-01

    A mixed suspension of red blood cells (RBCs) and microparticles flows through a cylindrical channel with a constriction mimicking a stenosed blood vessel. Our three-dimensional Lattice-Boltzmann simulations show that the RBCs are depleted right ahead of and after the constriction. Although the RBC mean concentration (hematocrit) is 16.5% or 23.7%, their axial concentration profile is very similar to that of isolated tracer particles flowing along the central axis. Most importantly, however, we find that the stiff microparticles exhibit the opposite behavior. Arriving on a marginated position near the channel wall, they can pass through the constriction only if they find a suitable gap to dip into the dense plug of RBCs occupying the channel center. This leads to a prolonged dwell time and, as a consequence, to a pronounced increase in microparticle concentration right in front of the constriction. For biochemically active particles such as drug delivery agents or activated platelets this clustering may have important physiological consequences, e.g., for the formation of microthrombi.

  9. Adipose tissue and skeletal muscle blood flow during mental stress

    Energy Technology Data Exchange (ETDEWEB)

    Linde, B.; Hjemdahl, P.; Freyschuss, U.; Juhlin-Dannfelt, A.

    1989-01-01

    Mental stress (a modified Stroop color word conflict test (CWT)) increased adipose tissue blood flow (ATBF; 133Xe clearance) by 70% and reduced adipose tissue vascular resistance (ATR) by 25% in healthy male volunteers. The vasculatures of adipose tissue (abdomen as well as thigh), skeletal muscle of the calf (133Xe clearance), and the entire calf (venous occlusion plethysmography) responded similarly. Arterial epinephrine (Epi) and glycerol levels were approximately doubled by stress. Beta-Blockade by metoprolol (beta 1-selective) or propranolol (nonselective) attenuated CWT-induced tachycardia similarly. Metoprolol attenuated stress-induced vasodilation in the calf and tended to do so in adipose tissue. Propranolol abolished vasodilation in the calf and resulted in vasoconstriction during CWT in adipose tissue. Decreases in ATR, but not in skeletal muscle or calf vascular resistances, were correlated to increases in arterial plasma glycerol (r = -0.42, P less than 0.05), whereas decreases in skeletal muscle and calf vascular resistances, but not in ATR, were correlated to increases in arterial Epi levels (r = -0.69, P less than 0.01; and r = -0.43, P less than 0.05, respectively). The results suggest that mental stress increases nutritive blood flow in adipose tissue and skeletal muscle considerably, both through the elevation of perfusion pressure and via vasodilatation. Withdrawal of vasoconstrictor nerve activity, vascular beta 2-adrenoceptor stimulation by circulating Epi, and metabolic mechanisms (in adipose tissue) may contribute to the vasodilatation.

  10. Local blood flow measured by fluorescence excitation of nonradioactive microspheres

    Energy Technology Data Exchange (ETDEWEB)

    Morita, Y.; Payne, B.D.; Aldea, G.S.; McWatters, C.; Husseini, W.; Mori, H.; Hoffman, J.I.; Kaufman, L. (Univ. of California, San Francisco (USA))

    1990-05-01

    An X-ray fluorescence system with low Compton background and high counting efficiency was developed to measure regional blood flow with nonradioactive microspheres. The performance of the system was tested in vitro by counting mixed aqueous solutions of either Mo, Ag, and I; Nb, Ag, and Ba; or Zr, Mo, Rh, Ag, Sn, I, and Ba, as well as a mixture of Ag and Ba nonradioactive microspheres. Mixtures containing 2-20 ppm of each element were counted for 10 min by the fluorescence system, and the individual elements in mixtures of three to seven nonradioactive elements were measured with high accuracy. The best counting statistics were obtained for Ag. For 10-min counts, the system measures as few as 120 Ag microspheres with 30% standard deviation but measures 800 Ag microspheres per sample with 3.6% standard deviation. We compared regional myocardial blood flows determined simultaneously by fluorescence and radioactive microsphere methods; the latter samples were counted by a 3-in. NaI (Tl) well detector and pulse-height analyzer. The radioactive and nonradioactive measurements showed good correlations.

  11. Modular Control Flow Analysis for Libraries

    DEFF Research Database (Denmark)

    Probst, Christian W.

    2002-01-01

    One problem in analyzing object oriented languages is that the exact control flow graph is not known statically due to dynamic dispatching. However, this is needed in order to apply the large class of known interprocedural analysis. Control Flow Analysis in the object oriented setting aims at det...... at determining run-time types of variables, thus allowing to possibly targeted method implementations. We present a flow sensitive analysis that allows separate handling of libraries and thereby efficient analysis of whole programs....

  12. Flow Control Over Sharp-Edged Wings

    Science.gov (United States)

    2007-07-01

    Sharp Leading Edge," Paper No. AIAA-2001-0121. 12Washburn, A. E., and Amitay, M., "Active Flow Control on the Stingray UAV: Physical Mechanisms," 4 2...A. E., and Amitay, M., "Active Flow Control on the Stingray UAV: Physical Mechanisms," 42 Aerospace Sciences Meeting & Exhibit," Paper No. AIAA-2004

  13. Flow Control in a Compact Inlet

    Science.gov (United States)

    Vaccaro, John C.

    2011-12-01

    An experimental investigation of flow control, via various control jets actuators, was undertaken to eliminate separation and secondary flows in a compact inlet. The compact inlet studied was highly aggressive with a length-to-diameter ratio of 1.5. A brand new facility was designed and built to enable various actuation methodologies as well as multiple measurement techniques. Techniques included static surface pressure, total pressure, and stereoscopic particle image velocimetry. Experimental data were supplemented with numerical simulations courtesy of Prof. Kenneth Jansen, Dr. Onkar Sahni, and Yi Chen. The baseline flow field was found to be dominated by two massive separations and secondary flow structures. These secondary structures were present at the aerodynamic interface plane in the form of two counter-rotating vortices inducing upwash along centerline. A dominant shedding frequency of 350 Hz was measured both at the aerodynamic interface plane and along the lower surface of the inlet. Flow control experiments started utilizing a pair of control jets placed in streamwise locations where flow was found to separate. Tests were performed for a range of inlet Mach numbers from 0.2 to 0.44. Steady and unsteady static pressure measurements along the upper and lower walls of the duct were performed for various combinations of actuation. The parameters that were tested include the control jets momentum coefficient, their blowing ratio, the actuation frequency, as well as different combinations of jets. It was shown that using mass flux ratio as a criterion to define flow control is not sufficient, and one needs to provide both the momentum coefficient and the blowing ratio to quantify the flow control performance. A detailed study was undertaken on controlling the upstream separation point for an inlet Mach number of 0.44. Similar to the baseline flow field, the flow field associated with the activation of a two-dimensional control jet actuator was dominated by

  14. Evaluation of Cutaneous Blood Flow During Lower Body Negative Pressure to Prevent Orthostatic Intolerance of Bedrest

    Science.gov (United States)

    Rubin, Marilyn

    1991-01-01

    Orthostatic tolerance is markedly impaired in most of the crewmembers during space flight and could seriously compromise crew safety during and immediately after landing. NASA investigators are studying the use of lower body negative pressure (LBNP) as a countermeasure to this intolerance. It is hypothesized that the continuously changing vascular pressure induced by sinusoidal LBNP with an additional countermeasure of salt and water will help crewmembers to be in a more acceptable physiologic condition to enter the earth's atmosphere. In ground based studies, subjects on bedrest provide the model for studying the physiologic effects of weightlessness. When subjects are treated with sinusoidal LBNP, negative pressures ranging from 0 to -60 mm/Hg are administered during a two hour period. This increases body fluids in the legs and lower body. This paper reports the results of two subjects who were placed on bedrest for six days. The subjects were randomly selected for either the control or treatment mode. The subject receiving the treatment mode ingested salt tablets and water on day 4 of the bedrest period. A ramp LBNP of two hours was next administered to this subject. The control subject did not receive anything during the bedrest period. Laser Doppler was used to measure the cutaneous blood flow of the forearm and calf to monitor vasoconstrictor effects of the baroreceptor reflex. Data indicated that skin blood flow in the treatment subject was higher than baseline in the forearm while the skin blood flow was decreased in the control subject.

  15. Effect of 0.2 % Brimonidine onRetinal Blood Flow

    Institute of Scientific and Technical Information of China (English)

    Minbin Yu; Yang Li; Xing Liu; Yunlan Ling; Xiaoping Zheng

    2001-01-01

    Purpose: To analyze the effect of 0.2 % brimonidine eye drops on retinal blood flow of patients with glaucoma. Methods: Using self-control method and Heidelberg Retina Flowmeter (HRF), we examined the volume, flow and velocity of the superior nasal and temporal, the inferior nasal and temporal artery of retina at baseline and 2 hours after single instillation of 0.2% brimonidine. Results: There were no significant changes in volume, fio~ and velocity of four vessels betore and after the administration of 0.2 % brimonidine. Conclusions: There are no significant ocular haemodvnamic benefits associated with Brimonidine therapy to the glaucoma patients. Eye Science 2001; 17:42 ~ 45.

  16. Blood flows and metabolic components of the cardiome.

    Science.gov (United States)

    Bassingthwaighte, J B; Li, Z; Qian, H

    1998-01-01

    This is a plan for the first stage of The Cardiome Project. The cardiome is the representation, in quantitative, testable form, of the functioning of the normal heart and its responses to intervention. The goal is to integrate the efforts of many years into a comprehensive understandable scheme. Past efforts have spanned the fields of transport within blood vessels, the distributions of regional coronary blood flows, permeation processes through capillary and cell walls, mediated cell membrane transport, extra- and intracellular diffusion, cardiac electrophysiology, the uptake and metabolism of the prime substrates (fatty acid and glucose), the metabolism of the purine nucleosides and nucleotides (mainly adenosine and ATP), the regulation of the ionic currents and of excitation-contraction coupling and finally the regulation of contraction. The central theme is to define the coronary flows and metabolic components of a computer model that will become a part of a three-dimensional heart with appropriate fibre shortening and volume ejection. The components are: (a) coronary flow distributions with appropriate heterogeneity, (b) metabolism of the substrates for energy production, (c) ATP, PCr and energy metabolism and (d) calcium metabolism as it relates to excitation-contraction coupling. The modeling should provide: (1) appropriate responses to regional ischemia induced by constriction of a coronary artery, including tissue contractility loss and aneurysmal dilation of the ischemic region; (2) physiological responses to rate changes such as treppe and changes in metabolic demand and (3) changes in local metabolic needs secondary to changes in the site of pacing stimulation and shortening inactivation or stretch activation of contraction.

  17. Regional cerebral blood flow and cognitive deficits in chronic lyme disease.

    Science.gov (United States)

    Fallon, Brian A; Keilp, John; Prohovnik, Isak; Heertum, Ronald Van; Mann, J John

    2003-01-01

    This study examined brain functioning in patients with Lyme encephalopathy. Eleven patients underwent neuropsychological tests and Xenon(133)-regional cerebral blood flow (rCBF) studies, using an external detector system. Each rCBF scan was age- and sex-matched to two archival, normal controls. While few differences were noted on gray-matter flow indices (ISI, fg), Lyme patients demonstrated significant flow reductions in white matter index (k(2)) (p=.004), particularly in the posterior temporal and parietal lobes bilaterally (p=.003). Flow reductions in white matter areas were significantly associated with deficits in memory (r=.66, p=.027) and visuospatial organization (r=.62, p=.041). Results suggest that Lyme encephalopathy may be a disease primarily affecting the cerebral white matter.

  18. A simple model of cerebral blood flow dependence on arterial blood pressure

    CERN Document Server

    Gersten, Alexander

    2011-01-01

    It is shown that the dependence of the cerebral blood flow (CBF) on mean arterial blood pressure (MABP) can be described with a simple model having the following assumptions. Below certain MABP (denoted as MABP1) there are no autoregulatory or feedback mechanisms influencing CBF. Between MABP1 and MABP2 (MABP at which breakthrough accurs) there is a linear (on MABP) dependent feedback with a sloap depending very much on the individual considered. The classical autoregulation model with a plateau in between MABP1 and MABP2 is a particular case of this model. The model describes well the experiments performed on dogs (Harper 1966), for which the individual feedback sloap parameter varied to great extent, indicating the importance of mesurments on individuals against averaged mesurments (or measurments on diffent individuals) which superficially support the classical autoregulation. New effect of decreased CBF, while increasing MABP, was observed.

  19. Effect of labetalol on cerebral blood flow and middle cerebral arterial flow velocity in healthy volunteers

    DEFF Research Database (Denmark)

    Schroeder, T; Schierbeck, Jens; Howardy, P;

    1991-01-01

    in normotensive subjects. Neither does it affect CO2 reactivity. The uniform results obtained with the two methods suggest TCD as a usable alternative to conventional CBF technique in the assessment of cerebral vasoactivity of various drugs in subjects with a normal cerebral circulation.......The effect of labetalol, a combined alpha- and beta-adrenoceptor antagonist, on the cerebral circulation was investigated in 7 normotensive subjects. Cerebral blood flow (CBF) was measured with the intravenous 133Xe method and mean flow velocity (Vmean) in the middle cerebral artery was determined...

  20. Absolute counting of neutrophils in whole blood using flow cytometry.

    Science.gov (United States)

    Brunck, Marion E G; Andersen, Stacey B; Timmins, Nicholas E; Osborne, Geoffrey W; Nielsen, Lars K

    2014-12-01

    Absolute neutrophil count (ANC) is used clinically to monitor physiological dysfunctions such as myelosuppression or infection. In the research laboratory, ANC is a valuable measure to monitor the evolution of a wide range of disease states in disease models. Flow cytometry (FCM) is a fast, widely used approach to confidently identify thousands of cells within minutes. FCM can be optimised for absolute counting using spiked-in beads or by measuring the sample volume analysed. Here we combine the 1A8 antibody, specific for the mouse granulocyte protein Ly6G, with flow cytometric counting in straightforward FCM assays for mouse ANC, easily implementable in the research laboratory. Volumetric and Trucount™ bead assays were optimized for mouse neutrophils, and ANC values obtained with these protocols were compared to ANC measured by a dual-platform assay using the Orphee Mythic 18 veterinary haematology analyser. The single platform assays were more precise with decreased intra-assay variability compared with ANC obtained using the dual protocol. Defining ANC based on Ly6G expression produces a 15% higher estimate than the dual protocol. Allowing for this difference in ANC definition, the flow cytometry counting assays using Ly6G can be used reliably in the research laboratory to quantify mouse ANC from a small volume of blood. We demonstrate the utility of the volumetric protocol in a time-course study of chemotherapy induced neutropenia using four drug regimens.

  1. Anatomical vertebral artery hypoplasia and insufficiency impairs dynamic blood flow regulation.

    Science.gov (United States)

    Sato, Kohei; Yoneya, Marina; Otsuki, Aki; Sadamoto, Tomoko; Ogoh, Shigehiko

    2015-11-01

    Recent studies have suggested that vertebral artery (VA) hypoplasia is a predisposing factor for posterior cerebral stroke. We examined whether anatomical vertebrobasilar ischemia, i.e., unilateral VA hypoplasia and insufficiency, impairs dynamic blood flow regulation. Twenty-eight female subjects were divided into three groups by defined criteria: (i) unilateral VA hypoplasia (n = 8), (ii) VA insufficiency (n = 6), and (iii) control (n = 14). Hypoplastic VA criterion was VA blood flow of 40 ml min(-1) , whereas VA insufficiency criterion was net (left + right) VA blood flow of 100 ml min(-1) or less. We evaluated left, right, and net VA blood flows by ultrasonography during hypercapnia, normocapnia, and hypocapnia to evaluate VA CO2 reactivity. The unilateral VA hypoplasia group showed lower CO2 reactivity at hypoplastic VA than at non-hypoplastic VA (2.65 ± 0.58 versus 3.00 ± 0.48% per mmHg, P = 0.027) and net VA CO2 reactivity was preserved (Unilateral VA hypoplasia, 2.95 ± 0.48 versus Control, 2.93 ± 0.42% per mmHg, P = 0.992). However, the VA insufficiency group showed a lower net VA CO2 reactivity compared to the control (2.29 ± 0.55 versus 2.93 ± 0.42% per mmHg, P = 0.032) and the unilateral VA hypoplasia (P = 0.046). VA hypoplasia reduced CO2 reactivity, although non-hypoplastic VA may compensate this regulatory limitation. In subjects with VA insufficiency, lowered CO2 reactivity at the both VA could not preserve normal net VA CO2 reactivity. These findings provide a possible physiological mechanism for the increased risk of posterior cerebral stroke in subjects with VA hypoplasia and insufficiency.

  2. An approach to automatic blood vessel image registration of microcirculation for blood flow analysis on nude mice.

    Science.gov (United States)

    Lin, Wen-Chen; Wu, Chih-Chieh; Zhang, Geoffrey; Wu, Tung-Hsin; Lin, Yang-Hsien; Huang, Tzung-Chi; Liu, Ren-Shyan; Lin, Kang-Ping

    2011-04-01

    Image registration is often a required and a time-consuming step in blood flow analysis of large microscopic video sequences in vivo. In order to obtain stable images for blood flow analysis, frame-to-frame image matching as a preprocessing step is a solution to the problem of movement during image acquisition. In this paper, microscopic system analysis without fluorescent labelling is performed to provide precise and continuous quantitative data of blood flow rate in individual microvessels of nude mice. The performance properties of several matching metrics are evaluated through simulated image registrations. An automatic image registration programme based on Powell's optimisation search method with low calculation redundancy was implemented. The matching method by variance of ratio is computationally efficient and improves the registration robustness and accuracy in practical application of microcirculation registration. The presented registration method shows acceptable results in close requisition to analyse red blood cell velocities, confirming the scientific potential of the system in blood flow analysis.

  3. Aminoguanidine effects on nerve blood flow, vascular permeability, electrophysiology, and oxygen free radicals

    Energy Technology Data Exchange (ETDEWEB)

    Kihara, Mikihiro; Schmelzer, J.D.; Poduslo, J.F.; Curran, G.L.; Nickander, K.K.; Low, P.A. (Mayo Foundation, Rochester, MN (United States))

    1991-07-15

    Since advanced glycosylation end products have been suggested to mediate hyperglycemia-induced microvascular atherogenesis and because aminoguanidine (AG) prevents their generation, the authors examined whether AG could prevent or ameliorate the physiologic and biochemical indices of streptozotocin (STZ)-induced experimental diabetic neuropathy. Four groups of adult Sprague-Dawley rats were studied: group I received STZ plus AG, group II received STZ plus AG, group III received STZ alone, and group IV was a control. They monitored conduction and action potential amplitudes serially in sciatic-tibial and caudal nerves, nerve blood flow, oxygen free radical activity (conjugated dienes and hydroperoxides), and the product of the permeability coefficient and surface area to {sup 125}I-labeled albumin. STZ-induced diabetes (group III) caused a 57% reduction in nerve blood flow and in abnormal nerve conduction and amplitudes and a 60% increase in conjugated dienes. Nerve blood flow was normalized by 8 weeks with AG (groups I and II) and conduction was significantly improved, in a dose-dependent manner, by 16 and 24 weeks in sciatic-tibial and caudal nerves, respectively. The permeability coefficient was not impaired, suggesting a normal blood-nerve barrier function for albumin, and the oxygen free-radical indices were not ameliorated by AG. They suggest that AG reverses nerve ischemia and more gradually improves their electrophysiology by an action on nerve microvessels. AG may have potential in the treatment of diabetic neuropathy.

  4. Power flow control using distributed saturable reactors

    Energy Technology Data Exchange (ETDEWEB)

    Dimitrovski, Aleksandar D.

    2016-02-13

    A magnetic amplifier includes a saturable core having a plurality of legs. Control windings wound around separate legs are spaced apart from each other and connected in series in an anti-symmetric relation. The control windings are configured in such a way that a biasing magnetic flux arising from a control current flowing through one of the plurality of control windings is substantially equal to the biasing magnetic flux flowing into a second of the plurality of control windings. The flow of the control current through each of the plurality of control windings changes the reactance of the saturable core reactor by driving those portions of the saturable core that convey the biasing magnetic flux in the saturable core into saturation. The phasing of the control winding limits a voltage induced in the plurality of control windings caused by a magnetic flux passing around a portion of the saturable core.

  5. Upper limit of cerebral blood flow autoregulation in experimental renovascular hypertension in the baboon

    DEFF Research Database (Denmark)

    Strandgaard, S; Jones, J V; MacKenzie, E T;

    1975-01-01

    The effect of arterial hypertension on cerebral blood flow was studied by the intracarotid 133Xe clearance method in baboons. The arterial blood pressure was raised in gradual steps with angiotensin. Baboons with renal hypertension of 8-12 weeks duration were studied along with normotensive baboons....... In initially normotensive baboons, cerebral blood flow remained constant until the mean arterial blood pressure had risen to the range of 140 to 154 mm Hg; thereafter cerebral blood flow increased with each rise in mean arterial blood pressure. In the chronically hypertensive baboons, cerebral blood flow...... remained constant until the mean arterial blood pressure had been elevated to the range of 155 to 169 mm Hg. Thus, in chronic hypertension it appears that there are adaptive changes in the cerebral circulation which may help to protect the brain from further increases in arterial blood pressure....

  6. Theory to predict shear stress on cells in turbulent blood flow.

    Science.gov (United States)

    Morshed, Khandakar Niaz; Bark, David; Forleo, Marcio; Dasi, Lakshmi Prasad

    2014-01-01

    Shear stress on blood cells and platelets transported in a turbulent flow dictates the fate and biological activity of these cells. We present a theoretical link between energy dissipation in turbulent flows to the shear stress that cells experience and show that for the case of physiological turbulent blood flow: (a) the Newtonian assumption is valid, (b) turbulent eddies are universal for the most complex of blood flow problems, and (c) shear stress distribution on turbulent blood flows is possibly universal. Further we resolve a long standing inconsistency in hemolysis between laminar and turbulent flow using the theoretical framework. This work demonstrates that energy dissipation as opposed to bulk shear stress in laminar or turbulent blood flow dictates local mechanical environment of blood cells and platelets universally.

  7. Dynamic Modeling of Renal Blood Flow in Dahl Hypertensive and Normotensive Rats

    DEFF Research Database (Denmark)

    Knudsen, Torben; Elmer, H.; Knudsen, Morten;

    2004-01-01

    A method is proposed in this paper which allows characterisation of renal autoregulatory dynamics and efficiency using quantitative mathematical methods. Based on data from rat experiments, where arterial blood pressure and renal blood flow are measured, a quantitative model for renal blood flow ...

  8. The Acute Effect of Resistance Exercise with Blood Flow Restriction with Hemodynamic Variables on Hypertensive Subjects

    Directory of Open Access Journals (Sweden)

    Araújo Joamira P.

    2014-12-01

    Full Text Available The purpose of this study was to analyze systolic blood pressure (SBP, diastolic blood pressure (DBP and the heart rate (HR before, during and after training at moderate intensity (MI, 50%-1RM and at low intensity with blood flow restriction (LIBFR. In a randomized controlled trial study, 14 subjects (average age 45±9,9 years performed one of the exercise protocols during two separate visits to the laboratory. SBP, DBP and HR measurements were collected prior to the start of the set and 15, 30, 45 and 60 minutes after knee extension exercises. Repeated measures of analysis of variance (ANOVA were used to identify significant variables (2 x 5; group x time. The results demonstrated a significant reduction in SBP in the LIBFR group. These results provide evidence that strength training performed acutely alters hemodynamic variables. However, training with blood flow restriction is more efficient in reducing blood pressure in hypertensive individuals than training with moderate intensity.

  9. Outcome of splanchnic blood flow determination in patients with suspected chronic intestinal ischaemia. A retrospective survey

    DEFF Research Database (Denmark)

    Møller, Søren; Madsen, Jan Lysgård

    2002-01-01

    flow: A, normal response (splanchnic blood flow > or = 200 ml/min); B, possible abnormal response (splanchnic blood flow 51-199 ml/min); and C, definitive abnormal response (splanchnic blood flow place, the type of operation was noted. RESULTS: Forty patients had...... a normal meal-induced response, 23 patients had a possible abnormal response and 10 patients had a definitive abnormal response, which gave evidence of chronic intestinal ischaemia. In the total patient population, the increase in splanchnic blood flow was significantly correlated to an increase in hepatic...

  10. Glucagon-like peptide-2 increases mesenteric blood flow in humans

    DEFF Research Database (Denmark)

    Bremholm, Lasse; Hornum, Mads; Henriksen, Birthe Merete;

    2008-01-01

    OBJECTIVE: Mesenteric blood flow is believed to be influenced by digestion and absorption of ingested macronutrients. We hypothesized that the intestinotrophic hormone, GLP-2 (glucagons-like peptide 2), may be involved in the regulation of mesenteric blood flow. Changes in mesenteric blood flow...... were measured by Doppler ultrasound scanning of the superior mesenteric artery (SMA). The aim of the study was to demonstrate the influence of GLP-2 on this flow, expressed as changes in resistance index (RI). MATERIAL AND METHODS: A homogeneous group of 10 fasting healthy volunteers completed a 2-day...... support the hypothesis that GLP-2 is an important regulator of mesenteric blood flow....

  11. Middle cerebral artery blood velocity and cerebral blood flow and O2 uptake during dynamic exercise

    DEFF Research Database (Denmark)

    Madsen, P L; Sperling, B K; Warming, T

    1993-01-01

    Results obtained by the 133Xe clearance method with external detectors and by transcranial Doppler sonography (TCD) suggest that dynamic exercise causes an increase of global average cerebral blood flow (CBF). These data are contradicted by earlier data obtained during less-well-defined conditions....... To investigate this controversy, we applied the Kety-Schmidt technique to measure the global average levels of CBF and cerebral metabolic rate of oxygen (CMRO2) during rest and dynamic exercise. Simultaneously with the determination of CBF and CMRO2, we used TCD to determine mean maximal flow velocity...... in the middle cerebral artery (MCA Vmean). For values of CBF and MCA Vmean a correction for an observed small drop in arterial PCO2 was carried out. Baseline values for global CBF and CMRO2 were 50.7 and 3.63 ml.100 g-1.min-1, respectively. The same values were found during dynamic exercise, whereas a 22% (P

  12. Cell-cell interaction in blood flow in patients with coronary heart disease (in vitro study)

    Science.gov (United States)

    Malinova, Lidia I.; Simonenko, Georgy V.; Denisova, Tatyana P.; Tuchin, Valery V.

    2007-02-01

    Blood cell-cell and cell-vessel wall interactions are one of the key patterns in blood and vascular pathophysiology. We have chosen the method of reconstruction of pulsative blood flow in vitro in the experimental set. Blood flow structure was studied by PC integrated video camera with following slide by slide analysis. Studied flow was of constant volumetric blood flow velocity (1 ml/h). Diameter of tube in use was comparable with coronary arteries diameter. Glucose solution and unfractured heparin were used as the nonspecial irritants of studied flow. Erythrocytes space structure in flow differs in all groups of patients in our study (men with stable angina pectoris (SAP), myocardial infarction (MI) and practically healthy men (PHM). Intensity of erythrocytes aggregate formation was maximal in patients with SAP, but time of their "construction/deconstruction" at glucose injection was minimal. Phenomena of primary clotting formation in patients with SAP of high function class was reconstructed under experimental conditions. Heparin injection (10 000 ED) increased linear blood flow velocity both in patients with SAP, MI and PHP but modulated the cell profile in the flow. Received data correspond with results of animal model studies and noninvasive blood flow studies in human. Results of our study reveal differences in blood flow structure in patients with coronary heart disease and PHP under irritating conditions as the possible framework of metabolic model of coronary blood flow destabilization.

  13. Acute stress reduces blood flow in the orofacial area, in conscious rabbits.

    Science.gov (United States)

    Roatta, Silvestro; Mohammed, Mazher; Passatore, Magda

    2009-04-01

    In the complex neurovascular control of the orofacial area, the only vasoconstrictor action is mediated by the sympathetic nervous system; however, its functional role is still unclear as little evidence exists of vasoconstrictor responses to physiological stimuli in both animal and human models. Aim of the present study was to investigate, orofacial vascular responses to acute stress in conscious rabbits. Twenty rabbits, implanted with chronic perivascular flow probes on the facial artery and with a telemetric probe for arterial blood pressure, were subjected to different alerting/stress stimuli, i.e., noise, taps on the rabbit's box, air jet, noxious cutaneous stimuli. Smaller groups of animal also underwent electromyographic (EMG) activity recording from the masseter muscle, unilateral section of the cervical sympathetic nerve (n=8), and alpha-adrenergic blockade with phentolamine (n=6). On average, all stressors evoked a pressor response accompanied by variable changes in heart rate and induced a marked, short-latency reduction in facial artery blood flow, corresponding to a decrease of 37-50% in vascular conductance of the facial artery. Local sympathetic denervation abolished the short-latency (15s) phase of the long-lasting response to the air jet. All vasoconstrictor effects were blocked by phentolamine. Increases in blood flow were observed only in concomitance with masseter EMG activity either during masticatory activity or in the form of brief occasional spontaneous contractions. This study provides evidence of an effective vasoconstrictor control by the sympathetic system in the orofacial area under stress conditions.

  14. A programmable and portable NMES device for drop foot correction and blood flow assist applications.

    Science.gov (United States)

    Breen, Paul P; Corley, Gavin J; O'Keeffe, Derek T; Conway, Richard; Olaighin, Gearóid

    2009-04-01

    The Duo-STIM, a new, programmable and portable neuromuscular stimulation system for drop foot correction and blood flow assist applications is presented. The system consists of a programmer unit and a portable, programmable stimulator unit. The portable stimulator features fully programmable, sensor-controlled, constant-voltage, dual-channel stimulation and accommodates a range of customized stimulation profiles. Trapezoidal and free-form adaptive stimulation intensity envelope algorithms are provided for drop foot correction applications, while time dependent and activity dependent algorithms are provided for blood flow assist applications. A variety of sensor types can be used with the portable unit, including force sensitive resistor-based foot switches and MEMS-based accelerometer and gyroscope devices. The paper provides a detailed description of the hardware and block-level system design for both units. The programming and operating procedures for the system are also presented. Finally, functional bench test results for the system are presented.

  15. Heat stress redistributes blood flow in arteries of the brain during dynamic exercise.

    Science.gov (United States)

    Sato, Kohei; Oue, Anna; Yoneya, Marina; Sadamoto, Tomoko; Ogoh, Shigehiko

    2016-04-01

    We hypothesized that heat stress would decrease anterior and posterior cerebral blood flow (CBF) during exercise, and the reduction in anterior CBF would be partly associated with large increase in extracranial blood flow (BF). Nine subjects performed 40 min of semirecumbent cycling at 60% of the peak oxygen uptake in hot (35°C; Heat) and thermoneutral environments (25°C; Control). We evaluated BF and conductance (COND) in the external carotid artery (ECA), internal carotid artery (ICA), and vertebral artery (VA) using ultrasonography. During the Heat condition, ICA and VA BF were significantly increased 10 min after the start of exercise (P brain arteries to exercise, which resulted in an alteration in the distribution of cardiac output. Moreover, a hyperthermia-induced increase in extracranial BF might compromise anterior CBF during exercise with heat stress.

  16. Local flow control for active building facades

    Science.gov (United States)

    Kaligotla, Srikar; Chen, Wayne; Glauser, Mark

    2010-11-01

    Existing building facade designs are for a passive and an impermeable shell to prevent migration of outdoor air into the building and to control heat transfers between the exterior environment and the building interior. An active facade that can respond in real time to changing environmental conditions like wind speed and direction, pollutant load, temperature, humidity and light can lower energy use and maximize occupant comfort. With an increased awareness of cost and environmental effects of energy use, cross or natural ventilation has become an attractive method to lower energy use. Separated flow regions around such buildings are undesirable due to high concentration of pollutants, especially if the vents or dynamic windows for cross ventilation are situated in these regions. Outside pollutant load redistribution through vents can be regulated via flow separation control to minimize transport of pollutants into the building. Flow separation has been substantially reduced with the application of intelligent flow control tools developed at Syracuse University for flow around "silo" (turret) like structures. Similar flow control models can be introduced into buildings with cross ventilation for local external flow separation control. Initial experiments will be performed for turbulent flow over a rectangular block (scaled to be a mid-rise building) that has been configured with dynamic vents and unsteady suction actuators in a wind tunnel at various wind speeds.

  17. Supersonic Plasma Flow Control Experiments

    Science.gov (United States)

    2005-12-01

    to liquid metals , for example, the conductivities of typical plasma and electrolyte flows are relatively low. Ref. 14 cites the conductivity of...heating is the dominant effect. 15. SUBJECT TERMS Supersonic, plasma , MHD , boundary-layer 16. SECURITY CLASSIFICATION OF: 19a. NAME OF RESPONSIBLE...horns in operation on Mach 5 wind tunnel with a plasma discharge. 31 Figure 17 Front view of a 100 mA DC discharge generated with upstream pointing

  18. Brain energy metabolism and blood flow differences in healthy aging

    DEFF Research Database (Denmark)

    Aanerud, Joel; Borghammer, Per; Chakravarty, M Mallar

    2012-01-01

    Cerebral metabolic rate of oxygen consumption (CMRO(2)), cerebral blood flow (CBF), and oxygen extraction fraction (OEF) are important indices of healthy aging of the brain. Although a frequent topic of study, changes of CBF and CMRO(2) during normal aging are still controversial, as some authors...... find decreases of both CBF and CMRO(2) but increased OEF, while others find no change, and yet other find divergent changes. In this reanalysis of previously published results from positron emission tomography of healthy volunteers, we determined CMRO(2) and CBF in 66 healthy volunteers aged 21 to 81......, and in the temporal cortex. Because of the inverse relation between OEF and capillary oxygen tension, increased OEF can compromise oxygen delivery to neurons, with possible perturbation of energy turnover. The results establish a possible mechanism of progression from healthy to unhealthy brain aging, as the regions...

  19. Numerical method of characteristics for one-dimensional blood flow

    CERN Document Server

    Acosta, Sebastian; Riviere, Beatrice; Penny, Daniel J; Rusin, Craig G

    2014-01-01

    Mathematical modeling at the level of the full cardiovascular system requires the numerical approximation of solutions to a one-dimensional nonlinear hyperbolic system describing flow in a single vessel. This model is often simulated by computationally intensive methods like finite elements and discontinuous Galerkin, while some recent applications require more efficient approaches (e.g. for real-time clinical decision support, phenomena occurring over multiple cardiac cycles, iterative solutions to optimization/inverse problems, and uncertainty quantification). Further, the high speed of pressure waves in blood vessels greatly restricts the time-step needed for stability in explicit schemes. We address both cost and stability by presenting an efficient and unconditionally stable method for approximating solutions to diagonal nonlinear hyperbolic systems. Theoretical analysis of the algorithm is given along with a comparison of our method to a discontinuous Galerkin implementation. Lastly, we demonstrate the ...

  20. Laser Doppler flowmetry to measure changes in cerebral blood flow.

    Science.gov (United States)

    Sutherland, Brad A; Rabie, Tamer; Buchan, Alastair M

    2014-01-01

    Laser Doppler flowmetry (LDF) is a method by which relative cerebral blood flow (CBF) of the cortex can be measured. Although the method is easy to employ, LDF only measures relative CBF, while absolute CBF cannot be quantified. LDF is useful for investigating CBF changes in a number of different applications including neurovascular and stroke research. This chapter will prepare the reader for rodent experiments using LDF with two preparations. The closed skull preparation can be used to monitor CBF with an intact skull, but in adult rats, thinning of the skull is required to obtain an accurate cortical CBF signal. The open skull preparation requires a craniotomy to expose the surface of the brain and the LDF probe is held close to the surface to measure cerebral perfusion.

  1. A dynamic model of renal blood flow autoregulation

    DEFF Research Database (Denmark)

    Holstein-Rathlou, N H; Marsh, D J

    1994-01-01

    To test whether a mathematical model combining dynamic models of the tubuloglomerular feedback (TGF) mechanism and the myogenic mechanism was sufficient to explain dynamic autoregulation of renal blood flow, we compared model simulations with experimental data. To assess the dynamic characteristics...... nephrons act in parallel, each simulation was performed with 125 parallel versions of the model. The key parameters of the 125 versions of the model were chosen randomly within the physiological range. None of the constituent models, i.e., the TGF and the myogenic, could alone reproduce the experimental...... observations. However, in combination they reproduced most of hte features of the various transfer functions calculated from the experimental data. The major discrepancy was the presence of a bimodal distribution of the admittance phase in the simulations. This is not consistent with most of the experimental...

  2. Biology and Mechanics of Blood Flows Part I: Biology

    CERN Document Server

    Thiriet, Marc

    2008-01-01

    Biology and Mechanics of Blood Flows presents the basic knowledge and state-of-the-art techniques necessary to carry out investigations of the cardiovascular system using modeling and simulation. Part I of this two-volume sequence, Biology, addresses the nanoscopic and microscopic scales. The nanoscale corresponds to the scale of biochemical reaction cascades involved in cell adaptation to mechanical stresses among other stimuli. The microscale is the scale of stress-induced tissue remodeling associated with acute or chronic loadings. The cardiovascular system, like any physiological system, has a complicated three-dimensional structure and composition. Its time dependent behavior is regulated, and this complex system has many components. In this authoritative work, the author provides a survey of relevant cell components and processes, with detailed coverage of the electrical and mechanical behaviors of vascular cells, tissues, and organs. Because the behaviors of vascular cells and tissues are tightly coupl...

  3. Coagulation on biomaterials in flowing blood: some theoretical considerations.

    Science.gov (United States)

    Basmadjian, D; Sefton, M V; Baldwin, S A

    1997-12-01

    Are truly inert biomaterials feasible? Recent mathematical models of coagulation which are reviewed here suggest that such materials are impossible. This conclusion, which is certainly consistent with our collective experimental evidence, arises from the calculation that conversion of Factor XI to XIa never drops to zero even at the highest flow rates and with virtually no Factor XIIa bound to a surface. Residual amounts of XIa are still formed which can in principle kick-off the coagulation cascade. Furthermore, if the flow rates and corresponding mass transfer coefficients are low and in spite of these near-vanishing levels of the initiating coagulants, the surprising result is that substantial amounts of thrombin are produced. On the contrary, under slightly higher flow conditions, there can be more substantial levels of initiating coagulants, yet paradoxically thrombin production is near zero. This article presents a theoretical understanding of the events which take place during the interaction of biomaterials with flowing blood. We follow these events from the time of first contact to the final production of thrombin. The effect of flow and surface activity on the contact phase reactions is examined in detail and the two are found to be intertwined. The common pathway is also examined and here the main feature is the existence of three flow dependent regions which produce either high or very low levels of thrombin, as well as multiple thrombin steady states. In a final analysis we link the two segments of the cascade and consider the events which result. In addition, we note that multiple steady states arise only in the presence of two (thrombin) feedback loops. Single loops or the bare cascade will produce only single steady states. With some imagination one can attribute to the feedback loops the role of providing the cascade with a mechanism to produce high thrombin levels in case of acute need (e.g. bleeding) or to allow levels to subside to 'stand

  4. Correlation study of uterine spiral artery blood flow characteristics with placental development and hypoxia in patients with preeclampsia

    Institute of Scientific and Technical Information of China (English)

    Rong Ma

    2016-01-01

    Objective:To study the correlation of uterine spiral artery blood flow characteristics with placental development and hypoxia in patients with preeclampsia.Methods:A total of 66 patients diagnosed with preeclampsia in our hospital between June 2013 and May 2016 were selected as the preeclampsia group (PE group) of the study and healthy women who gave birth in our hospital during the same period were selected as control group. At 32-37 weeks of gestation, uterine spiral artery ultrasonography was conducted to determine blood flow parameters PI, RI and S/D, and peripheral blood was collected to separate mononuclear cells and then determine CTLA-4 and CD28 mRNA level; after childbirth, placenta tissue was collect to determine the levels of placental development-related cytokines and apoptotic molecules.Results: Uterine spiral artery RI, PI and S/D of PE group were significantly higher than those of control group; PLGF, NGF, EGF, IGF-I, VEGF, Xiap, Survivin, bcl-2 and CD28 content in placenta tissue of PE group were significantly lower than those of control group and negatively correlated with uterine spiral artery PI, RI and S/D while GDF-15, caspase-3, caspase-9 and CTLA-4 content were significantly higher than those of control group and positively correlated with uterine spiral artery PI, RI and S/D; CTLA-4 mRNA level in peripheral blood mononuclear cells of PE group was significantly higher than that of control group and positively correlated with uterine spiral artery were PI, RI and S/D while CD28 mRNA level was significantly lower than that of control group and negatively correlated with uterine spiral artery PI, RI and S/D.Conclusion:Uterine spiral artery blood flow resistance increases and blood flow volume decreases in patients with preeclampsia, and the above blood flow characteristics will hinder the placental development, induce cell apoptosis and aggravate the placental hypoxia.

  5. TFRC—IVS Flow Control Algorithm

    Institute of Scientific and Technical Information of China (English)

    HEKaijian; LINYaping; YANGAng

    2003-01-01

    This paper investigates the TCP (Trans-mission Control Protocol) friendliness of multicast video-conferencing systems. Through the analysis and simulation experiments it is shown that the slow response to network state changes and the fixed rate adjustment process lead to TCP unfriendliness in the bandwidth sharing. Therefore,this paper proposes a new TCP friendly flow control al-gorithm called TFRC-IVS flow control algorithm for the current best-effort Internet. TFRC-IVS (TCP-Friendly Rate Control--INRIA Videoconferencing System) algo-rithm utilizes TCP friendly control function derived from complex TCP model to calculate TCP friendly sending rate.Simulation results show that TFRC-IVS flow control algorithm improves the smoothness of transmission rates and converges quickly to the stable sending rate. In addi-tion, the TCP friendly control function in TFRC-IVS flow control algorithm ensures the TCP friendliness of video flows and fair bandwidth allocation with TCP flows, which the traditional static rate adjustment algorithm lacks.

  6. Specification and Construction of Control Flow Semantics

    OpenAIRE

    Smelik, R.; Rensink, A.; Kastenberg, H.; Grundy, J.; Howse, J.

    2006-01-01

    In this paper we propose a visual language CFSL for specifying control flow semantics of programming languages. We also present a translation from CFSL to graph production systems (GPS) for flow graph construction; that is, any CFSL specification, say for a language L, gives rise to a GPS that constructs from any L-program (represented as an abstract syntax graph) the corresponding flow graph. The specification language is rich enough to capture complex language constructs, including all of J...

  7. Renal blood flow regulation and arterial pressure fluctuations: a case study in nonlinear dynamics

    DEFF Research Database (Denmark)

    Holstein-Rathlou, N H; Marsh, D J

    1994-01-01

    The arterial blood pressure, a physiological variable on which all renal excretory processes depend, fluctuates over a wide range of amplitudes and frequencies. Much of this variation originates in nonrenal vascular beds to support nonrenal tasks, and the fluctuations provide a noisy environment...... a relatively noise-free environment in which to work. Because of the time-varying nature of the blood pressure, we have concentrated in this review on the now substantial body of work on the dynamics of renal blood flow regulation and the underlying mechanisms. Renal vascular control mechanisms are not simply...... of experimental hypertension provide tubular pressure records that pass statistical tests for ordered structure and sensitive dependence on initial conditions in the reconstructed state space, two of the hallmarks of deterministic chaos. These records also pass recent more stringent tests for chaos...

  8. Nitric oxide and prostaglandins influence local skeletal muscle blood flow during exercise in humans: coupling between local substrate uptake and blood flow

    DEFF Research Database (Denmark)

    Kalliokoski, Kari K; Langberg, Henning; Ryberg, Ann Kathrine;

    2006-01-01

    skeletal muscle. Skeletal muscle blood flow was measured in seven healthy young men using near-infrared spectroscopy and indocyanine green and muscle glucose uptake using positron emission tomography and 2-fluoro-2-deoxy-D-[(18)F]glucose without and with local blockade of NO and PG at rest and during one-legged...... dynamic knee-extension exercise. Local blockade was produced by infusing nitro-L-arginine methyl ester and indomethacin directly in the muscle via a microdialysis catheter. Blood flow and glucose uptake were measured in the region of blockade and in two additional regions of vastus lateralis muscle 1......Synergic action of nitric oxide (NO) and prostaglandins (PG) in the regulation of muscle blood flow during exercise has been demonstrated. In the present study, we investigated whether these vasodilators also regulate local blood flow, flow heterogeneity, and glucose uptake within the exercising...

  9. Subcutaneous blood flow in the temporal region of migraine patients

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, K.

    1987-01-01

    Subcutaneous blood flow in the temporal region (TSBF) was measured by the local 133 Xenon washout technique in 43 migraine patients; 19 were reexamined in the course of spontaneous attacks. During attacks, TSBF was normal compared to headache-free state. In 13 unilateral attacks, the median ipsilateral to contralateral ratio TSBF was 1: 1.276, (NS). During 30 deg C passive head-up tilt, TSBF descreased by a median of 27% during headache-free intervals and by a median, 21% during migraine attacks. The difference between the 2 occasions was not significant. Head-up tilt resulted in a median 4.5% increase in mean arterial blood pressure (MAP) and a median 5.3% increase in heart rate (HR) during headache-free intervals and 3.4% and 3.2% respectively during migraine attacks. These results are evidence against a vasomotor disturbance of the extracranial tissues during attacks of migraine. The cardio-vascular response to the orthostatic stimulus indicates a normal function of this part of the autonomic nervous system during migraine attacks.

  10. Influence of remote ischemic preconditioning on cerebral oxygen metabolism and cerebral blood flow indexes of patients with ischemic cerebrovascular disease

    Institute of Scientific and Technical Information of China (English)

    Hui Lu; Ning-Ning Cui; Bin-Cheng Wang

    2016-01-01

    Objective:To study the influence of remote ischemic preconditioning on cerebral oxygen metabolism and cerebral blood flow indexes of patients with ischemic cerebrovascular disease. Methods:A total of 58 patients with ischemic cerebrovascular disease in our hospital from April 2015 to January 2016 were selected as the study object, and 58 patients were randomly divided into two groups, 29 patients in control group were treated with routine treatment, 29 patients in observation group were treated with remote ischemic preconditioning on the basic treatment of control group, then the cerebral oxygen metabolism and cerebral blood flow indexes of two groups before the treatment and at first, third and sixth month after the treatment were respectively detected and compared.Results:The cerebral oxygen metabolism and cerebral blood flow indexes of two groups before the treatment all showed no significant differences (allP>0.05), while the cerebral oxygen metabolism and cerebral blood flow indexes of observation group at first, third and sixth month after the treatment were all significantly better than those before the treatment, and the results were all significantly better than those of control group at the same time too (allP>0.05).Conclusions: The influence of remote ischemic preconditioning on cerebral oxygen metabolism and cerebral blood flow indexes of patients with ischemic cerebrovascular disease are better, and its application value for the patients with ischemic cerebrovascular disease is higher.

  11. Flow Control in a Transonic Diffuser

    Science.gov (United States)

    Gartner, Jeremy; Amitay, Michael

    2014-11-01

    In some airplanes such as fighter jets and UAV, short inlet ducts replace the more conventional ducts due to their shorter length. However, these ducts are associated with low length-to-diameter ratio and low aspect ratio and, thus, experience massive separation and the presence of secondary flow structures. These flow phenomena are undesirable as they lead to pressure losses and distortion at the Aerodynamic Interface Plane (AIP), where the engine face is located. It causes the engine to perform with a lower efficiency as it would with a straight duct diffuser. Different flow control techniques were studied on the short inlet duct, with the goal to reattach the flow and minimize the distortions at the AIP. Due to the complex interaction between the separation and the secondary flow structures, the necessity to understand the flow mechanisms, and how to control them at a more fundamental level, a new transonic diffuser with an upper ramp and a straight floor was designed and built. The objective of this project is to explore the effectiveness of different flow control techniques in a high subsonic (up to Mach 0.8) diffuser, so that the quasi two-dimensional separation and the formation of secondary flow structure can be isolated using a canonical flow field. Supported by Northrop Grumman.

  12. Blood flow and oxygenation in peritendinous tissue and calf muscle during dynamic exercise in humans

    DEFF Research Database (Denmark)

    Boushel, R; Langberg, Henning; Green, Stefan Mathias;

    2000-01-01

    1. Circulation around tendons may act as a shunt for muscle during exercise. The perfusion and oxygenation of Achilles' peritendinous tissue was measured in parallel with that of calf muscle during exercise to determine (1) whether blood flow is restricted in peritendinous tissue during exercise......, and (2) whether blood flow is coupled to oxidative metabolism. 2. Seven individuals performed dynamic plantar flexion from 1 to 9 W. Radial artery and popliteal venous blood were sampled for O2, peritendinous blood flow was determined by 133Xe-washout, calf blood flow by plethysmography, cardiac output...... by dye dilution, arterial pressure by an arterial catheter-transducer, and muscle and peritendinous O2 saturation by spatially resolved spectroscopy (SRS). 3. Calf blood flow rose 20-fold with exercise, reaching 44 +/- 7 ml (100 g)-1 min-1 (mean +/- s.e.m. ) at 9 W, while Achilles' peritendinous flow...

  13. Skeletal blood flow in Paget's disease of bone and its response to calcitonin therapy.

    Science.gov (United States)

    Wootton, R; Reeve, J; Spellacy, E; Tellez-Yudilevich, M

    1978-01-01

    1. Blood flow to the skeleton was measured by the 18F clearance method of Wooton, Reeve & Veall (1976) in 24 patients with untreated Paget's disease. In every patient but one, resting skeletal blood flow was increased. There was a significant positive correlation between skeletal blood flow and serum alkaline phosphatase and between skeletal blood flow and urinary total hydroxyproline excretion. 2. Fourteen patients were re-studied after they had received short-term (7 days or less) or long-term (7 weeks or more) calcitonin. Skeletal blood flow, alkaline phosphatase and urinary hydroxy-proline excretion fell towards normal in every case. There was some evidence from the short-term studies that calcitonin produced a more rapid fall in skeletal blood flow than in alkaline phosphatase. 3. Glomerular filtration rate appeared to increase transiently in response to calcitonin.

  14. Timing and topography of cerebral blood flow, aura, and headache during migraine attacks

    DEFF Research Database (Denmark)

    Olesen, J; Friberg, L; Olsen, T S

    1990-01-01

    and statistically significant spatial relations. The first observable event was a decrease of regional cerebral blood flow posteriorly in one cerebral hemisphere. Further development of this pathological process was accompanied by the aura symptoms. Thereafter headache occurred while regional cerebral blood flow...... remained decreased. During the headache phase, regional cerebral blood flow gradually changed from abnormally low to abnormally high without apparent change in headache. In some patients headache disappeared while regional cerebral blood flow remained increased. Although regional cerebral blood flow...... reduction and aura symptoms in the great majority of patients were unilateral, one-third had bilateral headache. Unilateral headache usually localized to the side on which regional cerebral blood flow was reduced and from which the aura symptoms originated (i.e., aura symptoms were perceived to occur...

  15. Dehydration affects cerebral blood flow but not its metabolic rate for oxygen during maximal exercise in trained humans

    DEFF Research Database (Denmark)

    Trangmar, Steven J; Chiesa, Scott T; Stock, Christopher G

    2014-01-01

    venous noradrenaline, and falling arterial carbon dioxide tension (P aCO 2) (R(2) ≥ 0.41, P ≤ 0.01) whereas CCA flow and conductance were related to elevated blood temperature. In conclusion, dehydration accelerated the decline in CBF by decreasing P aCO 2 and enhancing vasoconstrictor activity. However......Intense exercise is associated with a reduction in cerebral blood flow (CBF), but regulation of CBF during strenuous exercise in the heat with dehydration is unclear. We assessed internal (ICA) and common carotid artery (CCA) haemodynamics (indicative of CBF and extra-cranial blood flow), middle...... cerebral artery velocity (MCA Vmean), arterial-venous differences and blood temperature in 10 trained males during incremental cycling to exhaustion in the heat (35°C) in control, dehydrated and rehydrated states. Dehydration reduced body mass (75.8 ± 3 vs. 78.2 ± 3 kg), increased internal temperature (38...

  16. Physiological non-Newtonian blood flow through single stenosed artery

    Science.gov (United States)

    Mamun, Khairuzzaman; Rahman, Mohammad Matiur; Akhter, Most. Nasrin; Ali, Mohammad

    2016-07-01

    A numerical simulation to investigate the Non-Newtonian modelling effects on physiological flows in a three dimensional idealized artery with a single stenosis of 85% severity. The wall vessel is considered to be rigid. Oscillatory physiological and parabolic velocity profile has been imposed for inlet boundary condition. Where the physiological waveform is performed using a Fourier series with sixteen harmonics. The investigation has a Reynolds number range of 96 to 800. Low Reynolds number k - ω model is used as governing equation. The investigation has been carried out to characterize two Non-Newtonian constitutive equations of blood, namely, (i) Carreau and (ii) Cross models. The Newtonian model has also been investigated to study the physics of fluid. The results of Newtonian model are compared with the Non-Newtonian models. The numerical results are presented in terms of pressure, wall shear stress distributions and the streamlines contours. At early systole pressure differences between Newtonian and Non-Newtonian models are observed at pre-stenotic, throat and immediately after throat regions. In the case of wall shear stress, some differences between Newtonian and Non-Newtonian models are observed when the flows are minimum such as at early systole or diastole.

  17. Airway blood flow response to dry air hyperventilation in sheep

    Energy Technology Data Exchange (ETDEWEB)

    Parsons, G.H.; Baile, E.M.; Pare, P.D.

    1986-03-01

    Airway blood flow (Qaw) may be important in conditioning inspired air. To determine the effect of eucapneic dry air hyperventilation (hv) on Qaw in sheep the authors studied 7 anesthetized open-chest sheep after 25 min. of warm dry air hv. During each period of hv the authors have recorded vascular pressures, cardiac output (CO), and tracheal mucosal and inspired air temperature. Using a modification of the reference flow technique radiolabelled microspheres were injected into the left atrium to make separate measurements after humid air and dry air hv. In 4 animals a snare around the left main pulmonary artery was used following microsphere injection to prevent recirculation (entry into L lung of microspheres from the pulmonary artery). Qaw to the trachea and L lung as measured and Qaw for the R lung was estimated. After the final injection the sheep were killed and bronchi (Br) and lungs removed. Qaw (trachea plus L lung plus R lung) in 4 sheep increased from a mean of 30.8 to 67.0 ml/min. Airway mucosal temp. decreased from 39/sup 0/ to 33/sup 0/C. The authors conclude that dry air hv cools airway mucosa and increases Qaw in sheep.

  18. A Pulsatile Flow Phantom for Image-Guided HIFU Hemostasis of Blood Vessels

    Science.gov (United States)

    Greaby, Robyn; Vaezy, Shahram

    2005-03-01

    A pulsatile flow phantom for studying ultrasound image-guided acoustic hemostasis in a controlled environment has been developed. An ex vivo porcine carotid artery was attached to the phantom and embedded in a visually and ultrasonically transparent gel. Heparinized porcine blood was pumped through the phantom. Power-Doppler and B-mode ultrasound were used to remotely target the HIFU focus to the site of a needle puncture. In nine trials, complete hemostasis was achieved after an average HIFU application of 55 +/- 34 seconds. The vessels remained patent after treatment. With this phantom, it will be possible to do controlled studies of ultrasound image-guided acoustic hemostasis.

  19. Traffic Flow Control In Automated Highway Systems

    OpenAIRE

    Alvarez, Luis; Horowitz, Roberto

    1997-01-01

    This report studies the problem of traffic control in the Automated Highway System (AHS) hierarchical architecture of the California PATH program. A link layer controller for the PATH AHS architecture is presented. It is shown that the proposed control laws stabilize the vehicular density and flow around predetermined profiles.

  20. Chronic intestinal ischaemia: measurement of the total splanchnic blood flow.

    Science.gov (United States)

    Zacho, Helle D

    2013-04-01

    A redundant collateral network between the intestinal arteries is present at all times. In case of ischaemia in the gastrointestinal tract, the collateral blood supply can develop further, thus accommodating the demand for oxygen even in the presence of significant stenosis or occlusion of the intestinal arteries without clinical symptoms of intestinal ischaemia. Symptoms of ischemia develop when the genuine and collateral blood supply no longer can accommodate the need for oxygen. Atherosclerosis is the most common cause of obliteration in the intestinal arteries. In chronic intestinal ischaemia (CII), the fasting splanchnic blood flow (SBF) is sufficient, but the postprandial increase in SBF is inadequate and abdominal pain will therefore develop in relation to food intake causing the patient to eat smaller meals at larger intervals with a resulting weight loss. Traditionally, the CII-diagnosis has exclusively been based upon morphology (angiography) of the intestinal arteries; however, substantial discrepancies between CII-symptoms and the presence of atherosclerosis/stenosis in the intestinal arteries have been described repeatedly in the literature impeding the diagnosis of CII. This PhD thesis explores a method to determine the total SBF and its potential use as a diagnostic tool in patients suspected to suffer from CII. The SBF can be measured using a continuous infusion of a tracer and catheterisation of a hepatic vein and an artery. By measuring the SBF before and after a standard meal it is possible to assess the ability or inability to enhance the SBF and thereby diagnosing CII. In Study I, measurement of SBF was tested against angiography in a group of patients suspected to suffer from CII due to pain and weight loss. A very good agreement between the postprandial increase in SBF and angiography was found. The method was validated against a well-established method independent of the hepatic extraction of tracer using pAH in a porcine model (study II

  1. Quantification of cerebral blood flow and its clinical usefulness. Application of SPECT to psychiatry

    Energy Technology Data Exchange (ETDEWEB)

    Matsuda, Hiroshi; Uema, Takeshi; Kogure, Daisuke; Takano, Harumasa; Terada, Tomo [National Center Hospital for Mental, Nervous and Muscular Disorders, Kodaira, Tokyo (Japan)

    1998-10-01

    Brain perfusion SPECT using {sup 99m}Tc-ethyl-cysteinate dimer ({sup 99m}Tc-ECD) was applied to psychiatric diseases with aid of statistical parametric mapping (SPM) for analysis of data. To evaluate influence of aging on brain perfusion, noninvasive measurements of cerebral blood flow using {sup 99m}Tc-ECD were performed in 53 normal volunteers, aged 18 to 87 years old. Mean cerebral blood flow (mCBF) was 43.9{+-}5.0 ml/100 g/min and showed weak negative correlation with aging (r=-0.451). Perisylvian cerebral cortices and medial frontal areas including anterior cingulate gyri showed greater negative correlation than other areas. These findings suggest the necessity of age-matched control regional CBF (rCBF) data to investigate rCBF abnormality in patients. Four drug-naive schizophrenic patients showed flow decrease in bilateral frontal and superior temporal areas and a left infero-posterior temporal area. Haloperidol administration induced flow decrease in bilateral frontal and left parietal areas, while flow increase in bilateral striatal and right hippocampal areas. Ten aged depressive patients showed flow decrease in bilateral frontal and left temporo-parietal areas. Even after remission patients showed flow decrease in the left frontal area as compared with normal subjects. Remission induced flow increase in the right frontal, right parietal, and right orbitofrontal areas compared with depression. These results suggest that CBF measurements using {sup 99m}Tc-ECD are useful for objective evaluation of regional abnormality in brain function in psychiatric diseases. (author)

  2. VOST Flow-Control Valve Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Two cryogenic flow-control valves of diameters 1/2" and 2" will be built and tested. Based on cryogenically-proven Venturi Off-Set Technology (VOST) they have no...

  3. Planning to Plan-Integrating Control Flow

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    In many planning situations, computation itself becomes a resource to be planned and scheduled. We model such computational resources as conventional resources which are used by control-flow actions, e.g., to direct the planning process. Control-flow actions and conventional actions are planned/scheduled in an integrated way and can interact with each other. Control-flow actions are then executed by the planning engine itself. The approach is illustrated by examples, e.g., for hierarchical planning, in which tasks that are temporally still far away impose only rough constraints on the current schedule, and control-flow tasks ensure that these tasks are refined as they approach the current time. Using the same mechanism, anytime algorithms can change appropriate search methods or parameters over time, and problems like scheduling critical time-outs for garbage collection can be made part of the planning itself.

  4. Extraction of the magnetohydrodynamic blood flow potential from the surface electrocardiogram in magnetic resonance imaging.

    Science.gov (United States)

    Nijm, Grace M; Swiryn, Steven; Larson, Andrew C; Sahakian, Alan V

    2008-07-01

    The magnetohydrodynamic effect generates voltages related to blood flow, which are superimposed on the electrocardiogram (ECG) used for gating during cardiac magnetic resonance imaging (MRI). A method is presented for extracting the magnetohydrodynamic signal from the ECG. The extracted magnetohydrodynamic blood flow potential may be physiologically meaningful due to its relationship to blood flow. Removal of the magnetohydrodynamic voltages from the ECG can potentially lead to improved gating and diagnostically useful ECGs.

  5. The application of blood flow measurements to the study of aging muscle.

    Science.gov (United States)

    McCully, K K; Posner, J D

    1995-11-01

    Blood flow to skeletal muscle is a potentially important factor in the reduction of muscle function associated with aging (sarcopenia). The main influence of reduced blood flow capacity on muscle function is in limiting oxidative metabolism. Direct measures of blood flow include: intravital-microscopy, plethysmography, radioactive microspheres, 133Xenon washout, thermodilution, and Doppler ultrasound. Indirect measurement of blood flow includes arm-to-ankle pressure index and the rate of phosphocreatine recovery after exercise. Several new methodologies have been developed to evaluate muscle blood flow, including color-Doppler imaging, magnetic resonance imaging/angiography (MRI/MRA), and near-infrared spectroscopy (NIRS). As adaptations of traditional techniques, these methods promise more precise information under less invasive conditions. MRI is an expensive and technically challenging method able to measure vessel location, blood flow, and wall diameter in blood vessels throughout the cardiac cycle. Color-Doppler provides excellent temporal resolution blood flow throughout the cardiac cycle, along with some anatomical information. NIRS is an inexpensive and portable technology that can measure changes in oxygen saturation and provide information on tissue oxygen delivery in studies of frailer and more difficult-to-study subjects. Muscle blood flow is not thought to limit oxidative metabolism under normal conditions in young individuals. However, it is not clear what happens to muscle blood flow in healthy older individuals. Reduced capillary density, less maximal blood flow, and a slower hyperemic flow response have been reported in some, but not all, studies. Further studies with the newer methodologies are needed to re-examine age-related changes in muscle blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)

  6. Skin and muscle components of forearm blood flow in directly heated resting man.

    Science.gov (United States)

    Detry, J.-M. R.; Brengelmann, G. L.; Rowell, L. B.; Wyss, C.

    1972-01-01

    Changes in forearm muscle blood flow (FMBF) during direct whole-body heating were measured in 17 normal subjects using three different methods. We conclude that FMBF is not increased by direct whole-body heating. Since renal and splanchnic blood flow fall 30% under these conditions, maximal total skin blood flow in 12 previously studied subjects can be estimated from the rise in cardiac output to be 7.6 L/min (3.0-11.1 L/min).

  7. BIFURCATION OF FLOW AND MASS TRANSPORT IN A CURVED BLOOD VESSEL

    Institute of Scientific and Technical Information of China (English)

    TAN Wenchang(谭文长); WEI Lan(魏兰); ZHAO Yaohua(赵耀华); TAKASHI Masuoka

    2003-01-01

    A numerical analysis of flow and concentration fields of macromolecules in a slightly curved blood vessel was carried out. Based on these results, the effect of the bifurcation of a flow on the mass transport in a curved blood vessel was discussed. The macromolecules turned out to be easier to deposit in the inner part of the curved blood vessel near the critical Dean number. Once the Dean number is higher than the critical number, the bifurcation of the flow appears. This bifurcation can prevent macromolecules from concentrating in the inner part of the curved blood vessel. This result is helpful for understanding the possible correlations between the blood dynamics and atherosclerosis.

  8. Noninvasive average flow and differential pressure estimation for an implantable rotary blood pump using dimensional analysis.

    Science.gov (United States)

    Lim, Einly; Karantonis, Dean M; Reizes, John A; Cloherty, Shaun L; Mason, David G; Lovell, Nigel H

    2008-08-01

    Accurate noninvasive average flow and differential pressure estimation of implantable rotary blood pumps (IRBPs) is an important practical element for their physiological control. While most attempts at developing flow and differential pressure estimate models have involved purely empirical techniques, dimensional analysis utilizes theoretical principles of fluid mechanics that provides valuable insights into parameter relationships. Based on data obtained from a steady flow mock loop under a wide range of pump operating points and fluid viscosities, flow and differential pressure estimate models were thus obtained using dimensional analysis. The algorithm was then validated using data from two other VentrAssist IRBPs. Linear correlations between estimated and measured pump flow over a flow range of 0.5 to 8.0 L/min resulted in a slope of 0.98 ( R(2) = 0.9848). The average flow error was 0.20 +/- 0.14 L/min (mean +/- standard deviation) and the average percentage error was 5.79%. Similarly, linear correlations between estimated and measured pump differential pressure resulted in a slope of 1.027 ( R(2) = 0.997) over a pressure range of 60 to 180 mmHg. The average differential pressure error was 1.84 +/- 1.54 mmHg and the average percentage error was 1.51%.

  9. Electroosmotic oscillatory flow of micropolar fluid in microchannels:application to dynamics of blood flow in microfluidic devices

    Institute of Scientific and Technical Information of China (English)

    JC MISRA; S CHANDRA; GC SHIT; PK KUNDU

    2014-01-01

    The electroosmotic flow of a micropolar fluid in a microchannel bounded by two parallel porous plates undergoing periodic vibration is studied. The equations for conservation of linear and angular momentums and Gauss’s law of charge distribution are solved within the framework of the Debye-H¨uckel approximation. The fluid velocity and microrotation are assumed to depend linearly on the Reynolds number. The study shows that the amplitude of microrotation is highly sensitive to the changes in the magnitude of the suction velocity and the width of the microchannel. An increase in the micropolar parameter gives rise to a decrease in the amplitude of microrotation. Numerical estimates reveal that the microrotation of the suspended microelements in blood also plays an important role in controlling the electro-osmotically actuated flow dynamics in micro-bio-fluidic devices.

  10. Noninvasive color Doppler sonography of uterine blood flow throughout pregnancy in sheep and goats.

    Science.gov (United States)

    Elmetwally, M; Rohn, K; Meinecke-Tillmann, S

    2016-04-01

    In contrast to cattle or horses, uterine blood flow in small ruminants has been investigated predominantly after surgical intervention and chronic instrumentation. The objective of the present study was to investigate the clinical applicability of noninvasive color Doppler sonography to characterize blood flow in the maternal uterine artery of sheep, n = 11 (18 pregnancies) and goats, n = 11 (20 pregnancies). The following parameters were measured transrectally or transabdominally: blood flow volume, time-averaged maximum velocity (TAMV), resistance index (RI), pulsatility index (PI), Time-averaged mean velocity, impedance of blood flow (AB or systolic/diastolic [S/D] velocity ratio), peak velocity of blood flow and blood flow acceleration. Examinations started 2 weeks after breeding and continued at 2-week intervals until parturition. Outcomes for sheep and goats were similar and will be discussed together. Based on noninvasive color Doppler sonography, blood flow volume increased (approximately 60-fold, P sheep and goats. Furthermore, for uterine artery blood flow, there was an effect of stage of pregnancy on PI and RI (P sheep and goats, respectively, and then decreased until parturition. Similar to PI and RI, vascular impedance of the uterine decreased (P < 0.0001) throughout pregnancy. This is apparently the first study using noninvasive color Doppler sonography of uterine blood flow throughout physiological pregnancy in small ruminants. Clearly, this technology facilitates repeated, noninvasive assessments, with great potential for future studies.

  11. Mathematical analysis of non-Newtonian blood flow in stenosis narrow arteries.

    Science.gov (United States)

    Sriyab, Somchai

    2014-01-01

    The flow of blood in narrow arteries with bell-shaped mild stenosis is investigated that treats blood as non-Newtonian fluid by using the K-L model. When skin friction and resistance of blood flow are normalized with respect to non-Newtonian blood in normal artery, the results present the effect of stenosis length. When skin friction and resistance of blood flow are normalized with respect to Newtonian blood in stenosis artery, the results present the effect of non-Newtonian blood. The effect of stenosis length and effect of non-Newtonian fluid on skin friction are consistent with the Casson model in which the skin friction increases with the increase of either stenosis length or the yield stress but the skin friction decreases with the increase of plasma viscosity coefficient. The effect of stenosis length and effect of non-Newtonian fluid on resistance of blood flow are contradictory. The resistance of blood flow (when normalized by non-Newtonian blood in normal artery) increases when either the plasma viscosity coefficient or the yield stress increases, but it decreases with the increase of stenosis length. The resistance of blood flow (when normalized by Newtonian blood in stenosis artery) decreases when either the plasma viscosity coefficient or the yield stress increases, but it decreases with the increase of stenosis length.

  12. In Vitro Model of Physiological and Pathological Blood Flow with Application to Investigations of Vascular Cell Remodeling.

    Science.gov (United States)

    Elliott, Winston; Scott-Drechsel, Devon; Tan, Wei

    2015-11-03

    Vascular disease is a common cause of death within the United States. Herein, we present a method to examine the contribution of flow dynamics towards vascular disease pathologies. Unhealthy arteries often present with wall stiffening, scarring, or partial stenosis which may all affect fluid flow rates, and the magnitude of pulsatile flow, or pulsatility index. Replication of various flow conditions is the result of tuning a flow pressure damping chamber downstream of a blood pump. Introduction of air within a closed flow system allows for a compressible medium to absorb pulsatile pressure from the pump, and therefore vary the pulsatility index. The method described herein is simply reproduced, with highly controllable input, and easily measurable results. Some limitations are recreation of the complex physiological pulse waveform, which is only approximated by the system. Endothelial cells, smooth muscle cells, and fibroblasts are affected by the blood flow through the artery. The dynamic component of blood flow is determined by the cardiac output and arterial wall compliance. Vascular cell mechano-transduction of flow dynamics may trigger cytokine release and cross-talk between cell types within the artery. Co-culture of vascular cells is a more accurate picture reflecting cell-cell interaction on the blood vessel wall and vascular response to mechanical signaling. Contribution of flow dynamics, including the cell response to the dynamic and mean (or steady) components of flow, is therefore an important metric in determining disease pathology and treatment efficacy. Through introducing an in vitro co-culture model and pressure damping downstream of blood pump which produces simulated cardiac output, various arterial disease pathologies may be investigated.

  13. MEASUREMENT OF REGIONAL BONE BLOOD FLOW IN THE CANINE MANDIBULAR RAMUS USING RADIOLABELLED TOAD RED BLOOD CELLS

    Institute of Scientific and Technical Information of China (English)

    毛驰; 王翰章

    1994-01-01

    Toad red blood cells were used to measure regional bone blood flow in the canine mandibular ramus.The blood cells were labelled with sodium pertechnetate and fixed in 10% formalin;they were 22×15 μm in size and had a specific gravity close to that of dog red blood cells.These cells had no discernible effect on systemic hemody-namics after injection,did not agglutinate,were well mixed and evenly distributed throughout the body,and were completely extracted in one circulation through the mandible.The mandibular ramus was divided into six regions,and the blood flow rates in each were found to be similar to those reported in previous studies with radiolabelled carbonized,microspheres.Furthermore,the blood flow distribution pattern of the mandibular ramus determined in this study was identical to that of our previous study using the bone-seeking radionuclide method.We suggest that radiolabelled toad red blood cells are an ideal marker for measuring regional blood flow in the canine mandible.

  14. Effects of friction massage of the popliteal fossa on blood flow velocity of the popliteal vein

    Science.gov (United States)

    Iwamoto, Koji; Mizukami, Masafumi; Asakawa, Yasutsugu; Endo, Yusuke; Takata, Yuichi; Yoshikawa, Kenichi; Yoshio, Masaharu

    2017-01-01

    [Purpose] Friction massage (friction) of the popliteal fossa is provided for the purpose of relieving pain related to circulatory disorders by improving venous flow in the lower legs. The purpose of this study is to verify the effects of enhancing the venous flow based on measuring the blood flow velocity of the popliteal vein before and after providing friction to the patients. [Subjects and Methods] Fifteen healthy male university students participated in the study. The Doppler ultrasonography (DU) was used to measure the blood flow velocity of the popliteal vein, in order to verify the effects of enhancing the venous flow by comparing the measured values before and after a friction massage. [Results] The result of comparing the blood flow velocity before and after providing friction showed that there was a significant increase after friction. [Conclusion] This study proved that friction to the popliteal fossa is effectively enhances venous flow by increasing the blood flow velocity in the popliteal vein.

  15. Changes of Blood Flow Volume in the Superior Mesenteric Artery and Brachial Artery with Abdominal Thermal Stimulation

    Directory of Open Access Journals (Sweden)

    Shin Takayama

    2011-01-01

    Full Text Available In traditional Chinese medicine, moxibustion is a local thermal therapy that is used for several conditions. Quantifying the effects of moxibustion therapy has been difficult because the treatment temperature depends on the physician's experience, and the temperature distribution in the target area is not uniform. This prospective observational study aims to quantify the effect of local thermal stimulation to the abdomen. We developed a heat transfer control device (HTCD for local thermal stimulation. Twenty-four healthy subjects were enrolled and they underwent abdominal thermal stimulation to the para-umbilical region with the device for 20 min. Blood flow volume in the superior mesenteric artery (SMA and brachial artery (BA, the heart rate and the blood pressure were measured at rest, 15 min after starting thermal stimulation and 10, 20, 30 and 40 min after completing thermal stimulation. Blood flow parameters were measured by high-resolution ultrasound. In the SMA, blood flow volume was significantly increased during thermal stimulation (, as well as at 10 min ( and 20 min ( after stimulation. In the BA, blood flow volume decreased at 40 min after stimulation (. In conclusion we could quantify the effect of local thermal stimulation with an HTCD and high-resolution ultrasound. Thermal stimulation of the para-umbilical region increased blood flow in the SMA 20 min after stimulation in healthy subjects.

  16. Thenar muscle blood flow and bone mineral in the forearms of lumberjacks.

    Science.gov (United States)

    Karjalainen, P; Alhava, E M; Valtola, J

    1975-02-01

    Forty lumberjacks who had used a chain saw for 0-20 years and who had no general disease affecting the bones were studied by measuring the thenar muscle blood flow of both hands by the 133-Xe local clearance method. Bone mineral in the left forearm in the region of cancellous and cortical bone was assessed by the 241-Am gamma ray attenuation method. Virbration was found to decrease the blood flow in the saw-bearing left hand compared with the right hand of the lumberjacks. The bone mineral density (g/vm-3) was lower in the forearm bones of the lumberjacks than in controls of the same age with healthy bones. Moreover the poorer the thenar muscle blood flow, the greater was the decrease in the mineral density of the distal radius. Measurement of the mineral density of the forearm bones by the gramma ray attenuation method can be used for early detection of bone lesions in traumatic vasospastic disease.

  17. Assessing regional cerebral blood flow in depression using 320-slice computed tomography.

    Directory of Open Access Journals (Sweden)

    Yiming Wang

    Full Text Available While there is evidence that the development and course of major depressive disorder (MDD symptomatology is associated with vascular disease, and that there are changes in energy utilization in the disorder, the extent to which cerebral blood flow is changed in this condition is not clear. This study utilized a novel imaging technique previously used in coronary and stroke patients, 320-slice Computed-Tomography (CT, to assess regional cerebral blood flow (rCBF in those with MDD and examine the pattern of regional cerebral perfusion. Thirty nine participants with depressive symptoms (Hamilton Depression Rating Scale 24 (HAMD24 score > 20, and Self-Rating Depression Scale (SDS score > 53 and 41 healthy volunteers were studied. For all subjects, 3 ml of venous blood was collected to assess hematological parameters. Transcranial Doppler (TCD ultrasound was utilized to measure parameters of cerebral artery rCBFV and analyse the Pulsatility Index (PI. 16 subjects (8 =  MDD; 8 =  healthy also had rCBF measured in different cerebral artery regions using 320-slice CT. Differences among groups were analyzed using ANOVA and Pearson's tests were employed in our statistical analyses. Compared with the control group, whole blood viscosity (including high\\middle\\low shear rateand hematocrit (HCT were significantly increased in the MDD group. PI values in different cerebral artery regions and parameters of rCBFV in the cerebral arteries were decreased in depressive participants, and there was a positive relationship between rCBFV and the corresponding vascular rCBF in both gray and white matter. rCBF of the left gray matter was lower than that of the right in MDD. Major depression is characterized by a wide range of CBF impairments and prominent changes in gray matter blood flow. 320-slice CT appears to be a valid and promising tool for measuring rCBF, and could thus be employed in psychiatric settings for biomarker and treatment response purposes.

  18. Cerebral blood flow and oxygen metabolism in dementia with Lewy bodies

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Yoshitomo; Takahashi, Satoshi; Yonezawa, Hisashi [Iwate Medical Univ., Morioka (Japan). School of Medicine

    2000-06-01

    Regional cerebral blood flow (rCBF), oxygen metabolism (rCMRO{sub 2}) and the oxygen extraction fraction (rOEF) were measured using the steady-state {sup 15}O technique and positron emission tomography (PET) in six patients with dementia with Lewy bodies (DLB), and compared with ten patients with Alzheimer disease (AD) and six normal controls. In the AD patients, rCBF and rCMRO{sub 2} were significantly decreased in the frontal, parietal, and temporal cortices compared with controls. In DLB patients, rCBF and rCMRO{sub 2} were decreased in the frontal, parietal, temporal, and occipital cortices compared with controls, and were decreased more diffusely than in AD patients. rCBF and rCMRO{sub 2} were significantly decreased in occipital cortex compared with AD patients. rOEF was significantly increased in the parieto-temporal cortex in AD patients compared with controls. In DLB patients, rOEF was significantly increased not only in the parieto-temporal cortex but also in the occipital and frontal cortices compared with controls, and was significantly increased in the occipital cortex compared with AD patients. The diffuse reduction of cerebral blood flow and oxygen metabolism including the occipital cortex may be related to visual hallucination and other visuospatial deficits frequently seen in DLB patients. The increase in rOEF may be mainly due to the reduction in the vascular bed associated with decreased activity in the vasodilatory cholinergic system. (author)

  19. Control of fully turbulent pipe flow

    Science.gov (United States)

    Kuehnen, Jakob; Hof, Bjoern

    2013-11-01

    We present a novel, very simple passive control technique, where a local modification of the flow profile by means of a stationary obstacle leads to full relaminarisation downstream. Relaminarisation is achieved about 50 diameters downstream of the control point. Since, in a smooth straight pipe, the flow remains laminar from that position significant reduction in skin friction can be accomplished. High-speed stereoscopic particle image velocimetry (S-PIV) has been used to investigate and capture the development of the transitional flow downstream the obstacle. We will present S-PIV measurements as well as pressure drop measurements and videos of the development of the flow during relaminarisation. The guiding fundamental principle behind our approach to control the velocity profile will be explained and discussed.

  20. Simple Radiowave-Based Method For Measuring Peripheral Blood Flow Project

    Science.gov (United States)

    Oliva-Buisson, Yvette J.

    2014-01-01

    Project objective is to design small radio frequency based flow probes for the measurement of blood flow velocity in peripheral arteries such as the femoral artery and middle cerebral artery. The result will be the technological capability to measure peripheral blood flow rates and flow changes during various environmental stressors such as microgravity without contact to the individual being monitored. This technology may also lead to an easier method of detecting venous gas emboli during extravehicular activities.

  1. Coupled Flow-Structure-Biochemistry Simulations of Dynamic Systems of Blood Cells Using an Adaptive Surface Tracking Method

    OpenAIRE

    Hoskins, M.H.; Kunz, R.F.; Bistline, J.E.; Dong, C.

    2009-01-01

    A method for the computation of low Reynolds number dynamic blood cell systems is presented. The specific system of interest here is interaction between cancer cells and white blood cells in an experimental flow system. Fluid dynamics, structural mechanics, six-degree-of freedom motion control and surface biochemistry analysis components are coupled in the context of adaptive octree-based grid generation. Analytical and numerical verification of the quasi-steady assumption for the fluid mecha...

  2. Uteroplacental blood flow measured by placental scintigraphy during epidural anaesthesia for caesarean section

    Energy Technology Data Exchange (ETDEWEB)

    Skjoeldebrand, A.; Eklund, J.; Johansson, H.; Lunell, N.-O.; Nylund, L.; Sarby, B.; Thornstroem, S. (Departments of Anaesthesiology, Obstetrics and Gynaecology and Medical Physics, Karolinska Institute at Huddinge University Hospital, Stockholm (Sweden))

    1990-01-01

    The uteroplacental blood flow was measured before and during epidural anaesthesia for caesarean section in 11 woman. The blood flow was measured with dynamic placental scintigraphy. After an i.v. injection of indium-113m chloride, the gamma radiation over the placenta was recorded with a computer-linked scintillation camera. The uteroplacental blood flow could be calculated from the isotope accumulation curve. The anaesthesia was performed with bupivacaine plain 0.5%, 18-22 ml and a preload of a balanced electrolyte solution 10 ml/kg b.w. was given. The placental blood flow decreased in eight patients and increased in three with a median change of -21%, not being statistically significant. No correlation between maternal blood pressure and placental blood flow was found. (author).

  3. Unsteady Aerodynamic Flow Control of Moving Platforms

    Science.gov (United States)

    2014-05-29

    This error will arguably be diminished further with the future tuning of the PID controller that implements the motor commands. III.3.3 Aerodynamic...model is still aligned with the flow or ‘fine tune ’ the SMA power if it needs a minor realignment. III.1.2 Centered Static Model Prior to examining...8217 fluidic control. In addition, a PID controller is developed to effect ’closed loop’ fluidic control with optimally timed synthetic jet operation

  4. Regional cerebral blood flow and glucose metabolism following transient forebrain ischemia.

    Science.gov (United States)

    Pulsinelli, W A; Levy, D E; Duffy, T E

    1982-05-01

    Progressive brain damage after transient cerebral ischemia may be related to changes in postischemic cerebral blood flow and metabolism. Regional cerebral blood flow (rCBF) and cerebral glucose utilization (rCGU) were measured in adult rats prior to, during (only rCBF), and serially after transient forebrain ischemia. Animals were subjected to 30 minutes of forebrain ischemia by occluding both common carotid arteries 24 hours after cauterizing the vertebral arteries. Regional CBF was measured by the indicator-fractionation technique using 4-iodo-[14C]-antipyrine. Regional CGU was measured by the 2-[14C]deoxyglucose method. The results were correlated with the distribution and progression of ischemic neuronal damage in animals subjected to an identical ischemic insult. Cerebral blood flow to forebrain after 30 minutes of moderate to severe ischemia (less than 10% control CBF) was characterized by 5 to 15 minutes of hyperemia; rCBF then fell below normal and remained low for as long as 24 hours. Post-ischemic glucose utilization in the forebrain, except in the hippocampus, was depressed below control values at 1 hour and either remained low (neocortex, striatum) or gradually rose to normal (white matter) by 48 hours. In the hippocampus, glucose utilization equaled the control value at 1 hour and fell below control between 24 and 48 hours. The appearance of moderate to severe morphological damage in striatum and hippocampus coincided with a late rise of rCBF above normal and with a fall of rCGU; the late depression of rCGU was usually preceded by a period during which metabolism was increased relative to adjacent tissue. Further refinement of these studies may help identify salvageable brain after ischemia and define ways to manipulate CBF and metabolism in the treatment of stroke.

  5. Flow around a semicircular cylinder with passive flow control mechanisms

    Science.gov (United States)

    Hamed, A. M.; Vega, J.; Liu, B.; Chamorro, L. P.

    2017-03-01

    Wind tunnel experiments were performed to study the effect of passive flow control strategies on the wake and drag of a semicircular cylinder of infinite aspect ratio. High-resolution planar particle image velocimetry was used to obtain flow statistics around the semicircular cylinder at Reynolds number Re≈ 3.2× 10^4 based on the cylinder diameter. The control mechanisms under consideration include rigid flaps of various lengths placed at the edges of the structure and a small slot along the symmetry plane of the cylinder. Mean velocity fields reveal the distinctive effects of each passive mechanism on the flow, such as velocity recovery, size of the recirculation bubble and location of the reattachment point. The distributions of turbulence kinetic energy and kinematic shear stress show the modulation of each passive control mechanism on the wake, including the onset and location of the maximum turbulence levels. Instantaneous and mean fields of swirling strength further highlight the role of the passive mechanisms in the vortex dynamics. Drag coefficient for the various cases was estimated indirectly from the flow measurements using a momentum balance. This approach shows that long flaps and slot were able to reduce drag with respect to the base case. The rigid flaps with length coincident with the diameter of the cylinder offered the best performance with drag reduction of ˜25%.

  6. Coupling between arterial and venous cerebral blood flow during postural change.

    Science.gov (United States)

    Ogoh, Shigehiko; Washio, Takuro; Sasaki, Hiroyuki; Petersen, Lonnie G; Secher, Niels H; Sato, Kohei

    2016-12-01

    In supine humans the main drainage from the brain is through the internal jugular vein (IJV), but the vertebral veins (VV) become important during orthostatic stress because the IJV is partially collapsed. To identify the effect of this shift in venous drainage from the brain on the cerebral circulation, this study addressed both arterial and venous flow responses in the "anterior" and "posterior" parts of the brain when nine healthy subjects (5 men) were seated and flow was manipulated by hyperventilation and inhalation of 6% carbon dioxide (CO2). From a supine to a seated position, both internal carotid artery (ICA) and IJV blood flow decreased (P = 0.004 and P = 0.002), while vertebral artery (VA) flow did not change (P = 0.348) and VV flow increased (P = 0.024). In both supine and seated positions the ICA response to manipulation of end-tidal CO2 tension was reflected in IJV (r = 0.645 and r = 0.790, P blood flow (r = 0.771 and r = 0.828, P blood flow did not affect venous outflow, but the decrease in IJV blood flow was associated with the increase in VV blood flow (r = 0.479, P = 0.044). In addition, the increase in VV blood flow when seated was reflected in VA blood flow (r = 0.649, P = 0.004), and the two flows were coupled during manipulation of the end-tidal CO2 tension (supine, r = 0.551, P = 0.004; seated, r = 0.612, P blood flow when seated and that VV may influence VA blood flow.

  7. Numerical Modeling of Interstitial Fluid Flow Coupled with Blood Flow through a Remodeled Solid Tumor Microvascular Network.

    Directory of Open Access Journals (Sweden)

    M Soltani

    Full Text Available Modeling of interstitial fluid flow involves processes such as fluid diffusion, convective transport in extracellular matrix, and extravasation from blood vessels. To date, majority of microvascular flow modeling has been done at different levels and scales mostly on simple tumor shapes with their capillaries. However, with our proposed numerical model, more complex and realistic tumor shapes and capillary networks can be studied. Both blood flow through a capillary network, which is induced by a solid tumor, and fluid flow in tumor's surrounding tissue are formulated. First, governing equations of angiogenesis are implemented to specify the different domains for the network and interstitium. Then, governing equations for flow modeling are introduced for different domains. The conservation laws for mass and momentum (including continuity equation, Darcy's law for tissue, and simplified Navier-Stokes equation for blood flow through capillaries are used for simulating interstitial and intravascular flows and Starling's law is used for closing this system of equations and coupling the intravascular and extravascular flows. This is the first study of flow modeling in solid tumors to naturalistically couple intravascular and extravascular flow through a network. This network is generated by sprouting angiogenesis and consisting of one parent vessel connected to the network while taking into account the non-continuous behavior of blood, adaptability of capillary diameter to hemodynamics and metabolic stimuli, non-Newtonian blood flow, and phase separation of blood flow in capillary bifurcation. The incorporation of the outlined components beyond the previous models provides a more realistic prediction of interstitial fluid flow pattern in solid tumors and surrounding tissues. Results predict higher interstitial pressure, almost two times, for realistic model compared to the simplified model.

  8. The effects of anisodamine and dobutamine on gut mucosal blood flow during gut ischemia/reperfusion

    Institute of Scientific and Technical Information of China (English)

    Sen Hu; Zhi-Yong Sheng

    2002-01-01

    AIM: To determine if anisodamine is able to augmentmucosal perfusion during gut I/R ischemia-reperfusion.METHODS: A jejunal sec wes formed in Sprague Dawley rat.A Laser Doppler probe and a tonometer were inserted intothe sac which was filled with saline. The superiormesenteric artery was occluded (SMAO)for 60 minutesfollowed by 90 minutes of reperfusion. At the end of 60minutes of SMAO, either 0. 2 mg/kg of anisodmine ordobutamine was injected into the jejunal sac. Laser Dopplermucosal blood flow and regional PCO2 ( PrCO2 )measurements were made.RESULTS: Mucosal blood flow was significantly increased at30,60 and 90 minutes of reperfusion (R30, R60, R90 ) whenintraluminal anisodamine or dobutamine was presentcompared to intraluminal saline only(44 + 3.3 % or 48 + 4. 1% vs37+2.6% atR30, 57+5.0% or56+4.7 % vs45+2.7% atR60, 64+3.3% or56+4.2 % vs48+3.4 % atR90,respectively P < 0. 05 ). Blood flow changes were alsoreflected by lowering of jejunal PrCO2 measurements afterintraluminal anisodamine or dobutamine compared with thatof the saline controls (41 + 3. 1 mmHg or 44 ± 3.0 mmHg vs49 + 3.7 mmHg at R30, 38 + 3.7 mmHg or 40 + 2. 1 mmHg vs 47+ 3.8 mmHg at R60, 34 + 2. 1 mmHg or 39 + 3.0 mmHg vs 46 3.4 mmHg at R90, respectively, P< 0.05). Most interestingfinding wes that there were significantly higher mucosalblood flow and lower jejunal PrCO2 in anisodamine groupthan those in dobutamine group at 90 minutes of reperfusion(64+ 3.3 % vs 56 + 4.2 % for blood flow or 34 + 2. 1 mmHgvs 39 + 3.0 mmHg for PrCO2, respectively, P < 0. 05 ),suggesting that anisodamine had a more lasting effect onmucosal perfusion than dobutamine.CONCLUSION: Intraluminal anisodamine and dobutaminecan augment mucosal blood flow during gut I/R and alleviatemucosal acidosis. The results provided benificial effects onthe treatment of splanchnic hypoperfusion followingtraumatic or burn shock.

  9. Intensive blood pressure lowering increases cerebral blood flow in older subjects with hypertension.

    Science.gov (United States)

    Tryambake, Dinesh; He, Jiabao; Firbank, Michael J; O'Brien, John T; Blamire, Andrew M; Ford, Gary A

    2013-06-01

    Hypertension is associated with reduced cerebral blood flow (CBF). Intensive (blood pressure (BP) lowering in older people might give greater reduction in cardiovascular risk, but there are concerns that this might produce hypoperfusion which may precipitate falls and possibly stroke. We determined the effect of intensive compared with usual BP lowering on CBF in hypertensive older subjects. Individuals aged >70 years with a history of systolic hypertension on 1 or no BP lowering drugs were recruited from primary care (n=37; age, 75±4 years; systolic BP, >150 mm Hg) and randomized to receive intensive (target BP, treatment. Baseline BP (ambulatory or in clinic) and baseline gray matter CBF were not significantly different between the groups. After treatment, BP was reduced significantly in both groups but fell more in the intensive group (26/17 versus 15/5 mm Hg; Phypertension increases CBF, compared with BP lowering to usual target. These findings suggest hypertension in older people shifts the autoregulatory CBF curve rightward and downward and is reversible with BP lowering.

  10. Comparison of instruments for investigation of microcirculatory blood flow and red blood cell concentration

    Science.gov (United States)

    O'Doherty, Jim; McNamara, Paul; Clancy, Neil T.; Enfield, Joey G.; Leahy, Martin J.

    2009-05-01

    The use of laser Doppler perfusion imaging (LDPI) and laser speckle perfusion imaging (LSPI) is well known in the noninvasive investigation of microcirculatory blood flow. This work compares the two techniques with the recently developed tissue viability (TiVi) imaging system, which is proposed as a useful tool to quantify red blood cell concentration in microcirculation. Three systems are evaluated with common skin tests such as the use of vasodilating and vasoconstricting drugs (methlynicotinate and clobetasol, respectively) and a reactive hyperaemia maneuver (using a sphygmomanometer). The devices investigated are the laser Doppler line scanner (LDLS), the laser speckle perfusion imager (FLPI)-both from Moor Instruments (Axminster, United Kingdom)-and the TiVi imaging system (WheelsBridge AB, Linköping, Sweden). Both imaging and point scanning by the devices are used to quantify the provoked reactions. Perfusion images of vasodilatation and vasoconstriction are acquired with both LDLS and FLPI, while TiVi images are acquired with the TiVi imager. Time acquisitions of an averaged region of interest are acquired for temporal studies such as the reactive hyperaemia. In contrast to the change in perfusion over time with pressure, the TiVi imager shows a different response due its measurement of blood concentration rather than perfusion. The responses can be explained by physiological understanding. Although the three devices sample different compartments of tissue, and output essentially different variables, comparisons can be seen between the three systems. The LDLS system proves to be suited to measurement of perfusion in deeper vessels, while FLPI and TiVi showed sensitivity to more superficial nutritional supply. LDLS and FLPI are insensitive to the action of the vasoconstrictor, while TiVi shows the clear boundaries of the reaction. Assessment of the resolution, penetration depth, and acquisition rate of each instrument show complimentary features that should

  11. Inflow/Outflow Boundary Conditions for Particle-Based Blood Flow Simulations: Application to Arterial Bifurcations and Trees.

    Science.gov (United States)

    Lykov, Kirill; Li, Xuejin; Lei, Huan; Pivkin, Igor V; Karniadakis, George Em

    2015-08-01

    When blood flows through a bifurcation, red blood cells (RBCs) travel into side branches at different hematocrit levels, and it is even possible that all RBCs enter into one branch only, leading to a complete separation of plasma and RBCs. To quantify this phenomenon via particle-based mesoscopic simulations, we developed a general framework for open boundary conditions in multiphase flows that is effective even for high hematocrit levels. The inflow at the inlet is duplicated from a fully developed flow generated in a pilot simulation with periodic boundary conditions. The outflow is controlled by adaptive forces to maintain the flow rate and velocity gradient at fixed values, while the particles leaving the arteriole at the outlet are removed from the system. Upon validation of this approach, we performed systematic 3D simulations to study plasma skimming in arterioles of diameters 20 to 32 microns. For a flow rate ratio 6:1 at the branches, we observed the "all-or-nothing" phenomenon with plasma only entering the low flow rate branch. We then simulated blood-plasma separation in arteriolar bifurcations with different bifurcation angles and same diameter of the daughter branches. Our simulations predict a significant increase in RBC flux through the main daughter branch as the bifurcation angle is increased. Finally, we demonstrated the effectiveness of the new methodology in simulations of blood flow in vessels with multiple inlets and outlets, constructed using an angiogenesis model.

  12. Nailfold capillaroscopy and blood flow laser-doppler analysis of the microvascular damage in systemic sclerosis: preliminary results

    Directory of Open Access Journals (Sweden)

    C. Pizzorni

    2011-06-01

    Full Text Available Objectives: Systemic sclerosis (SSc is characterized by altered microvascular structure and function. Nailfold videocapillaroscopy (NVC is the tool to evaluate capillary morphological structure and laser-Doppler Blood flowmetry (LDF can be used to estimate cutaneous blood flow of microvessels. The aim of this study was to investigate possible relationships between capillary morphology and blood flow in SSc. Methods: 27 SSc patients and 12 healthy subjects were enrolled. SSc microvascular involvement, as evaluated by NVC, was classified in three different patterns (“Early”, “Active”, “Late”. LDF analysis was performed at the II, III, IV, V hand fingers in both hands and both at cutaneous temperature and at 36°C. Statistical evaluation was carried out by non-parametric procedures. Results: Blood flow was found significantly lower in SSc patients when compared with healthy subjects (p<0.05. The heating of the probe to 36°C induced a significant increase in peripheral blood flow in all subjects compared to baseline (p <0.05, however, the amount of variation was significantly lower in patients with SSc, compared with healthy controls (p <0.05. The SSc patients with NVC “Late” pattern, showed lower values of peripheral blood flow than patients with NVC “Active” or “Early” patterns (p<0.05. Moreover, a negative correlation between the tissue perfusion score and the progression of the SSc microangiopathy was observed, as well as between the tissue perfusion and the duration of the Raynaud’s phenomenon (p <0.03. Conclusions: LDF can be employed to evaluate blood perfusion in the microvascular circulation in SSc patients. The blood flow changes observed with the LDF seem to correlate with the severity of microvascular damage in SSc as detected by NVC.

  13. In vivo analysis of physiological 3D blood flow of cerebral veins

    Energy Technology Data Exchange (ETDEWEB)

    Schuchardt, Florian; Schroeder, Laure; Baeuerle, Jochen; Harloff, Andreas [University Medical Centre, Department of Neurology, Freiburg (Germany); Anastasopoulos, Constantin [University Medical Center, Department of Neuropaediatrics and Muscle Disorders, Freiburg (Germany); University Medical Centre, Department of Neuroradiology, Freiburg (Germany); Markl, Michael [Northwestern University, Department of Radiology, Feinberg School of Medicine and McCormick School of Engineering, Chicago, IL (United States); Hennemuth, Anja; Drexl, Johann [Fraunhofer MEVIS, Bremen (Germany); Valdueza, Jose M. [Neurological Center, Segeberger Kliniken, Bad Segeberg (Germany); Mader, Irina [University Medical Centre, Department of Neuroradiology, Freiburg (Germany)

    2015-08-15

    To visualize and quantify physiological blood flow of intracranial veins in vivo using time-resolved, 3D phase-contrast MRI (4D flow MRI), and to test measurement accuracy. Fifteen healthy volunteers underwent repeated ECG-triggered 4D flow MRI (3 Tesla, 32-channel head coil). Intracranial venous blood flow was analysed using dedicated software allowing for blood flow visualization and quantification in analysis planes at the superior sagittal, straight, and transverse sinuses. MRI was evaluated for intra- and inter-observer agreement and scan-rescan reproducibility. Measurements of the transverse sinuses were compared with transcranial two-dimensional duplex ultrasound. Visualization of 3D blood flow within cerebral sinuses was feasible in 100 % and within at least one deep cerebral vein in 87 % of the volunteers. Blood flow velocity/volume increased along the superior sagittal sinus and was lower in the left compared to the right transverse sinus. Intra- and inter-observer reliability and reproducibility of blood flow velocity (mean difference 0.01/0.02/0.02 m/s) and volume (mean difference 0.0002/-0.0003/0.00003 l/s) were good to excellent. High/low velocities were more pronounced (8 % overestimation/9 % underestimation) in MRI compared to ultrasound. Four-dimensional flow MRI reliably visualizes and quantifies three-dimensional cerebral venous blood flow in vivo and is promising for studies in patients with sinus thrombosis and related diseases. (orig.)

  14. Regional cerebral blood flow in normal pressure hydrocephalus: diagnostic and prognostic aspects

    Energy Technology Data Exchange (ETDEWEB)

    Larsson, A. (Dept. of Neurology, Sahlgren Hospital, Goeteborg (Sweden)); Bergh, A.C. (Dept. of Clinical Physiology, Sahlgren Hospital, Goeteborg (Sweden)); Bilting, M. (Dept. of Neurosurgery, Sahlgren Hospital, Goeteborg (Sweden)); Aerlig, AA. (Dept. of Radiation Physics, Sahlgren Hospital, Goeteborg (Sweden)); Jacobsson, L. (Dept. of Radiation Physics, Sahlgren Hospital, Goeteborg (Sweden)); Stephensen, H. (Dept. of Neurosurgery, Sahlgren Hospital, Goeteborg (Sweden)); Wikkelsoe, C. (Dept. of Neurology, Sahlgren Hospital, Goeteborg (Sweden))

    1994-02-01

    Relative regional cerebral blood flow (rrCBF) was measured by SPET using [sup 99m]Tc-HMPAO as flow tracer, in 23 patients with normal pressure hydrocephalus (NPH). 1000 MBq [sup 99m]Tc-HMPAO was given intravenously and the rrCBF calculated as regional/cerebellar count level ratios. The patients were examined before and 3-12 months after ventriculoperitoneal shunt surgery. rrCBF was also determined in ten healthy aged matched volunteers who served as controls. The NPH patients had decreased rrCBF in the hippocampal regions and in the frontal and parietal white matter as compared to the controls. The frontal/parietal rrCBF ratio correlated with both psychiatric disability and the preoperative degree of incontinence. Decreased flow in frontal white matter, frontoparietal and hippocampal grey matter and a low frontalparietal grey matter flow ratio preoperatively correlated with improvement in both Mini Mental State score and psychiatric disability after shunt surgery. After shunt surgery the rrCBF increased in the mesencephalon, frontal grey and white matter, parietal white matter and hippocampus. The flow increase in hippocampal regions and frontal white matter correlated with improvement in psychiatric symptomatology. The results of this study regarding the frontal and hippocampal rrCBF patterns, and the clinical correlation, support the hypothesis that CBF changes in these regions are of patohphysiological and prognostic importance in NPH. (orig./MG)

  15. Fast Blood Vector Velocity Imaging using ultrasound: In-vivo examples of complex blood flow in the vascular system

    DEFF Research Database (Denmark)

    Hansen, Kristoffer Lindskov; Udesen, Jesper; Gran, Fredrik;

    2008-01-01

    speckle tracking between segments in consecutive speckle images. The flow patterns of six bifurcations and two veins were investigated in-vivo. It was shown: 1) that a stable vortex in the carotid bulb was present opposed to other examined bifurcations, 2) that retrograde flow was present......Conventional ultrasound methods for acquiring color flow images of the blood motion are restricted by a relatively low frame rate and angle dependent velocity estimates. The Plane Wave Excitation (PWE) method has been proposed to solve these limitations. The frame rate can be increased, and the 2-D...... vector velocity of the blood motion can be estimated. The transmitted pulse is not focused, and a full speckle image of the blood can be acquired for each emission. A 13 bit Barker code is transmitted simultaneously from each transducer element. The 2-D vector velocity of the blood is found using 2-D...

  16. The reproducibility of cerebral blood flow with N-isopropyl-p-({sup 123}I) iodoamphetamine by arterial blood sampling method

    Energy Technology Data Exchange (ETDEWEB)

    Sasaki, Kazufumi; Tamura, Kiyohiko [Akita Univ. (Japan). Hospital; Hirano, Hiroko; Oyama, Yoichi; Kobayashi, Mitsuru; Tomura, Noriaki; Watari, Jiro

    1997-12-01

    The reproducibility of cerebral blood flow (CBF) based on the microsphere model with N-isopropyl-p-({sup 123}I) iodoamphetamine (IMP), was evaluated 4.58% (=CV) and was within 9%. The former was calculated from the elementary experiments, the latter was calculated with the CBF of 11 cases. On the clinical conditions, where we selected some astrocytomas of grade III injected ACNU super selectively with Seldinger catheter, and quantified CBF both pre and post ACNU ia by the ROI of 16.2 mm{phi}. On the other hand we have been monitoring the Cross Calibration Factors (CCFs) since we started CBF quantification. The CCFs during 5 years were all within the upper and the lower control limits. At a worst case the average deviation of CCF was 1.17% by a month, which is equal to 7.0% by 6 months. Then SPECT and well counter should be calibrated at least once every 6 months. (author)

  17. Determining tumor blood flow parameters from dynamic image measurements

    Science.gov (United States)

    Libertini, Jessica M.

    2008-11-01

    Many recent cancer treatments focus on preventing angiogenesis, the process by which a tumor promotes the growth of large and efficient capillary beds for the increased nourishment required to support the tumor's rapid growth[l]. To measure the efficacy of these treatments in a timely fashion, there is an interest in using data from dynamic sequences of contrast-enhanced medical imaging, such as MRI and CT, to measure blood flow parameters such as perfusion, permeability-surface-area product, and the relative volumes of the plasma and extracellular-extravascular space. Starting with a two compartment model presented by the radiology community[2], this work challenges the application of a simplification to this problem, which was originally developed to model capillary reuptake[3]. While the primary result of this work is the demonstration of the inaccuracy of this simplification, the remainder of the paper is dedicated to presenting alternative methods for calculating the perfusion and plasma volume coefficients. These methods are applied to model data sets based on real patient data, and preliminary results are presented.

  18. Determining tumor blood flow parameters from dynamic image measurements

    Energy Technology Data Exchange (ETDEWEB)

    Libertini, Jessica M [Division of Applied Mathematics, Brown University, Providence, Rhode Island 02906 (United States)], E-mail: Jessica_Libertini@brown.edu

    2008-11-01

    Many recent cancer treatments focus on preventing angiogenesis, the process by which a tumor promotes the growth of large and efficient capillary beds for the increased nourishment required to support the tumor's rapid growth. To measure the efficacy of these treatments in a timely fashion, there is an interest in using data from dynamic sequences of contrast-enhanced medical imaging, such as MRI and CT, to measure blood flow parameters such as perfusion, permeability-surface-area product, and the relative volumes of the plasma and extracellular-extravascular space. Starting with a two compartment model presented by the radiology community, this work challenges the application of a simplification to this problem, which was originally developed to model capillary reuptake. While the primary result of this work is the demonstration of the inaccuracy of this simplification, the remainder of the paper is dedicated to presenting alternative methods for calculating the perfusion and plasma volume coefficients. These methods are applied to model data sets based on real patient data, and preliminary results are presented.

  19. Autoregulation of cerebral blood flow in experimental focal brain ischemia.

    Science.gov (United States)

    Dirnagl, U; Pulsinelli, W

    1990-05-01

    The relationship between systemic arterial pressure (SAP) and neocortical microcirculatory blood-flow (CBF) in areas of focal cerebral ischemia was studied in 15 spontaneously hypertensive rats (SHRs) anesthetized with halothane (0.5%). Ischemia was induced by ipsilateral middle cerebral artery/common carotid artery occlusion and CBF was monitored continuously in the ischemic territory using laser-Doppler flowmetry during manipulation of SAP with I-norepinephrine (hypertension) or nitroprusside (hypotension). In eight SHRs not subjected to focal ischemia, we demonstrated that 0.5% halothane and the surgical manipulations did not impair autoregulation. Autoregulation was partly preserved in ischemic brain tissue with a CBF of greater than 30% of preocclusion values. In areas where ischemic CBF was less than 30% of preocclusion values, autoregulation was completely lost. Changes in SAP had a greater influence on CBF in tissue areas where CBF ranged from 15 to 30% of baseline (9% change in CBF with each 10% change in SAP) than in areas where CBF was less than 15% of baseline (6% change in CBF with each 10% change in SAP). These findings demonstrate that the relationship between CBF and SAP in areas of focal ischemia is highly dependent on the severity of ischemia. Autoregulation is lost in a gradual manner until CBF falls below 30% of normal. In areas without autoregulation, the slope of the CBF/SAP relationship is inversely related to the degree of ischemia.

  20. Cerebral blood flow in sickle cell cerebrovascular disease

    Energy Technology Data Exchange (ETDEWEB)

    Huttenlocher, P.R.; Moohr, J.W.; Johns, L.; Brown, F.D.

    1984-05-01

    Cerebral blood flow (CBF) has been studied by the xenon-133 (/sup 133/Xe) inhalation method in 16 children with suspected sickle cell cerebrovascular disease. Abnormalities consisting of decreases in total, hemispheral, or regional CBF were found in 17 of 26 studies. Eleven studies performed immediately after stroke, transient ischemic attack, or depression of state of alertness showed abnormalities. In addition to confirming regional cerebrovascular insufficiency in children with stroke due to major cerebral artery occlusion, the method detected diffuse decrease in CBF in children with stupor, coma, and seizures who had normal angiographic findings. In contrast, six of seven studies obtained after exchange transfusion or during maintenance on hypertransfusion therapy showed normal findings. The difference between results in patients with acute neurologic disturbances and those receiving transfusion therapy was statistically significant (P less than .005). The data indicate that the /sup 133/Xe method reliably demonstrates cerebrovascular impairment in sickle cell disease. They also suggest that CBF changes in patients with sickle cell disease can be reversed by exchange transfusion and by hypertransfusion therapy. The /sup 133/Xe CBF method may be useful for following up children with sickle cell disease who are at high risk for recurrent stroke.