Changes in extracellular muscle volume affect heart rate and blood pressure responses to static exercise

Science.gov (United States)

Baum, K.; Essfeld, D.; Stegemann, J.

To investigate the effect of μg-induced peripheral extracellular fluid reductions on heart rate and blood pressure during isometric exercise, six healthy male subjects performed three calf ergometer test with different extracellular volumes of working muscles. In all tests, body positions during exercise were identical (supine with the knee joint flexed to 900). After a pre-exercise period of 25 min, during which calf volumes were manipulated, subjects had to counteract an external force of 180 N for 5 min. During the pre-exercise period three different protocols were applied. Test A: Subjects rested in the exercise position; test B: Body position was the same as in A but calf volume was increased by venous congestion (cuffs inflated to 80 mm Hg); test C: Calf volumes were decreased by a negative hydrostatic pressure (calves about 40 cm above heart level with the subjects supine). To clamp the changed calf volumes in tests B and C, cuffs were inflated to 300 mm Hg 5 min before the onset of exercise. This occlusion was maintained until termination of exercise. Compared to tests A and B, the reduced volume of test C led to significant increases in heart rate and blood pressure during exercise. Oxygen uptake did not exceed resting levels in B and C until cuffs were deflated, indicating that exclusively calf muscles contributed to the neurogenic peripheral drive. It is concluded that changes in extracellular muscle volume have to be taken into account when comparing heart rate and blood pressure during lg- and μg- exercise.

Hemodynamic differences between continual positive and two types of negative pressure ventilation.

Science.gov (United States)

Lockhat, D; Langleben, D; Zidulka, A

1992-09-01

In seven anesthetized dogs, ventilated with matching lung volumes, tidal volumes, and respiratory rates, we compared the effects on cardiac output (CO), arterial venous oxygen saturation difference (SaO2 - SVO2), and femoral and inferior vena cava pressure (1) intermittent positive pressure ventilation with positive end-expiratory pressure (CPPV); (2) iron-lung ventilation with negative end-expiratory pressure (ILV-NEEP); (3) grid and wrap ventilation with NEEP applied to the thorax and upper abdomen (G&W-NEEP). The values of CO and SaO2 - SVO2 with ILV-NEEP were similar to those with CPPV. However, with G&W-NEEP as compared with ILV-NEEP, mean CO was greater (2.9 versus 2.6 L/min, p = 0.02) and mean (SaO2 - SVO2) was lower (26.6% versus 28.3%, p = NS). Mean PFEM-IVC was higher with G&W-NEEP than with the other types of ventilation. We conclude that (1) ILV-NEEP is hemodynamically equivalent to CPPV and (2) G&W-NEEP has less adverse hemodynamic consequences. has less adverse hemodynamic consequences.

Influence of upper body position on middle cerebral artery blood velocity during continuous positive airway pressure breathing

DEFF Research Database (Denmark)

Højlund Rasmussen, J; Mantoni, T; Belhage, B

2007-01-01

Continuous positive airway pressure (CPAP) is a treatment modality for pulmonary oxygenation difficulties. CPAP impairs venous return to the heart and, in turn, affects cerebral blood flow (CBF) and augments cerebral blood volume (CBV). We considered that during CPAP, elevation of the upper body ...

Geophysics Under Pressure: Large-Volume Presses Versus the Diamond-Anvil Cell

Science.gov (United States)

Hazen, R. M.

2002-05-01

Prior to 1970, the legacy of Harvard physicist Percy Bridgman dominated high-pressure geophysics. Massive presses with large-volume devices, including piston-cylinder, opposed-anvil, and multi-anvil configurations, were widely used in both science and industry to achieve a range of crustal and upper mantle temperatures and pressures. George Kennedy of UCLA was a particularly influential advocate of large-volume apparatus for geophysical research prior to his death in 1980. The high-pressure scene began to change in 1959 with the invention of the diamond-anvil cell, which was designed simultaneously and independently by John Jamieson at the University of Chicago and Alvin Van Valkenburg at the National Bureau of Standards in Washington, DC. The compact, inexpensive diamond cell achieved record static pressures and had the advantage of optical access to the high-pressure environment. Nevertheless, members of the geophysical community, who favored the substantial sample volumes, geothermally relevant temperature range, and satisfying bulk of large-volume presses, initially viewed the diamond cell with indifference or even contempt. Several factors led to a gradual shift in emphasis from large-volume presses to diamond-anvil cells in geophysical research during the 1960s and 1970s. These factors include (1) their relatively low cost at time of fiscal restraint, (2) Alvin Van Valkenburg's new position as a Program Director at the National Science Foundation in 1964 (when George Kennedy's proposal for a Nation High-Pressure Laboratory was rejected), (3) the development of lasers and micro-analytical spectroscopic techniques suitable for analyzing samples in a diamond cell, and (4) the attainment of record pressures (e.g., 100 GPa in 1975 by Mao and Bell at the Geophysical Laboratory). Today, a more balanced collaborative approach has been adopted by the geophysics and mineral physics community. Many high-pressure laboratories operate a new generation of less expensive

Pressure and volume in the first law of black hole thermodynamics

Science.gov (United States)

Dolan, Brian P.

2011-12-01

The mass of a black hole is interpreted, in terms of thermodynamic potentials, as being the enthalpy, with the pressure given by the cosmological constant. The volume is then defined as being the Legendre transform of the pressure, and the resulting relation between volume and pressure is explored in the case of positive pressure. A virial expansion is developed and a van der Waals like critical point determined. The first law of black hole thermodynamics includes a PdV term which modifies the maximal efficiency of a Penrose process. It is shown that, in four-dimensional spacetime with a negative cosmological constant, an extremal charged rotating black hole can have an efficiency of up to 75%, while for an electrically neutral rotating black hole this figure is reduced to 52%, compared to the corresponding values of 50% and 29% respectively when the cosmological constant is zero.

Pressure and volume in the first law of black hole thermodynamics

International Nuclear Information System (INIS)

Dolan, Brian P

2011-01-01

The mass of a black hole is interpreted, in terms of thermodynamic potentials, as being the enthalpy, with the pressure given by the cosmological constant. The volume is then defined as being the Legendre transform of the pressure, and the resulting relation between volume and pressure is explored in the case of positive pressure. A virial expansion is developed and a van der Waals like critical point determined. The first law of black hole thermodynamics includes a PdV term which modifies the maximal efficiency of a Penrose process. It is shown that, in four-dimensional spacetime with a negative cosmological constant, an extremal charged rotating black hole can have an efficiency of up to 75%, while for an electrically neutral rotating black hole this figure is reduced to 52%, compared to the corresponding values of 50% and 29% respectively when the cosmological constant is zero. (paper)

FCT (functional computed tomography) evaluation of the lung volumes at different PEEP (positive-end expiratory pressure) ventilation pattern, in mechanical ventilated patients

International Nuclear Information System (INIS)

Papi, M.G.; Di Segni, R.; Mazzetti, G.; Staffa, F.; Conforto, F.; Calimici, R.; Salvi, A.; Matteucci, G.

2007-01-01

Purpose To evaluate with FCT (functional computed tomography) total lung volume and fractional lung volumes at different PEEP (positive end expiratory pressure) values in acute mechanically ventilated patients. Methods Nine ICU (intensive care unity) patients (1 lung pneumonia, 2 polytrauma, 2 sepsis, 3 brain surgery, 1 pulmonary embolism); mean age 48 ± 15 years, 6 male, 3 female; GE 16 MDCT scan was performed with acquisition from apex to diaphragma in seven seca at different PEEP values. Raw CT data were analysed by an advantage workstation to obtain volume density masks and histograms of both lungs and each lung and these density ranges were applied: - 1000 - 950 hyper-ventilated lung, -900 - 650 well aerated lung, -950 - 500 all aerated lung, -500 + 200 lung tissue. Total and fractional lung volumes, Hounsfield unit (HU) were calculated and compared at different PEEP values (0, 5, 10, 15 cm H 2 O). In four patients lung volumes were compared between the more and the less involved lung at increased PEEP. Statistic analysis: comparison means-medians tests. Results Data calculated at five PEEP showed unexpected decrease of total lung volume and increase of lung density (HU); proportionally no significant improvement of oxigenation. (orig.)

FCT (functional computed tomography) evaluation of the lung volumes at different PEEP (positive-end expiratory pressure) ventilation pattern, in mechanical ventilated patients

Energy Technology Data Exchange (ETDEWEB)

Papi, M.G.; Di Segni, R.; Mazzetti, G.; Staffa, F. [Dept. of Radiology, S. Giovanni HS, Rome (Italy); Conforto, F.; Calimici, R.; Salvi, A. [Dept. of Anesthesiology, S. Giovanni HS, Rome (Italy); Matteucci, G. [Dept. of Pneumology, S. Giovanni HS, Rome (Italy)

2007-06-15

Purpose To evaluate with FCT (functional computed tomography) total lung volume and fractional lung volumes at different PEEP (positive end expiratory pressure) values in acute mechanically ventilated patients. Methods Nine ICU (intensive care unity) patients (1 lung pneumonia, 2 polytrauma, 2 sepsis, 3 brain surgery, 1 pulmonary embolism); mean age 48 {+-} 15 years, 6 male, 3 female; GE 16 MDCT scan was performed with acquisition from apex to diaphragma in seven seca at different PEEP values. Raw CT data were analysed by an advantage workstation to obtain volume density masks and histograms of both lungs and each lung and these density ranges were applied: - 1000 - 950 = hyper-ventilated lung, -900 - 650 well aerated lung, -950 - 500 all aerated lung, -500 + 200 lung tissue. Total and fractional lung volumes, Hounsfield unit (HU) were calculated and compared at different PEEP values (0, 5, 10, 15 cm H{sub 2}O). In four patients lung volumes were compared between the more and the less involved lung at increased PEEP. Statistic analysis: comparison means-medians tests. Results Data calculated at five PEEP showed unexpected decrease of total lung volume and increase of lung density (HU); proportionally no significant improvement of oxigenation. (orig.)

Simultaneous pressure-volume measurements using optical sensors and MRI for left ventricle function assessment during animal experiment.

Science.gov (United States)

Abi-Abdallah Rodriguez, Dima; Durand, Emmanuel; de Rochefort, Ludovic; Boudjemline, Younes; Mousseaux, Elie

2015-01-01

Simultaneous pressure and volume measurements enable the extraction of valuable parameters for left ventricle function assessment. Cardiac MR has proven to be the most accurate method for volume estimation. Nonetheless, measuring pressure simultaneously during MRI acquisitions remains a challenge given the magnetic nature of the widely used pressure transducers. In this study we show the feasibility of simultaneous in vivo pressure-volume acquisitions with MRI using optical pressure sensors. Pressure-volume loops were calculated while inducing three inotropic states in a sheep and functional indices were extracted, using single beat loops, to characterize systolic and diastolic performance. Functional indices evolved as expected in response to positive inotropic stimuli. The end-systolic elastance, representing the contractility index, the diastolic myocardium compliance, and the cardiac work efficiency all increased when inducing inotropic state enhancement. The association of MRI and optical pressure sensors within the left ventricle successfully enabled pressure-volume loop analysis after having respective data simultaneously recorded during the experimentation without the need to move the animal between each inotropic state. Copyright © 2014 IPEM. Published by Elsevier Ltd. All rights reserved.

Continuous Positive Airway Pressure (CPAP)

Science.gov (United States)

... ENT Doctor Near You Continuous Positive Airway Pressure (CPAP) Continuous Positive Airway Pressure (CPAP) Patient Health Information ... relations staff at newsroom@entnet.org . What Is CPAP? The most common and effective nonsurgical treatment for ...

Beat-by-beat analysis of cardiac output and blood pressure responses to short-term barostimulation in different body positions

Science.gov (United States)

Hildebrandt, Wulf; Schütze, Harald; Stegemann, J.

Rapid quantification of the human baro-reflex control of heart rate has been achieved on a beat-by-beat basis using a neck-chamber with quick ECG-triggered pressure changes. Referring to recent findings on heart rate and stroke volume, the present study uses this technique to compare cardiac output as well as blood pressure changes in supine and upright position to investigate feedback effects and to confirm postural reflex modifications not revealed by RR-interval changes. A suction profile starting at +40 mmHg and running 7 steps of pressure decrease down to -65 mmHg was examined in 0° and 90° tilting position while beat-by-beat recordings were done of heart rate, stroke volume (impedance-cardiography) and blood pressure (Finapres tm) (n=16). The percentual heart rate decrease failed to be significantly different between positions. A suction-induced stroke volume increase led to a cardiac output almost maintained when supine and significantly increased when upright. A decrease in all blood pressure values was found during suction, except for systolic values in upright position which increased. Conclusively, (a) it is confirmed that different inotropy accounts for the seen gravitational effect on the cardiac output not represented by heart rate; (b) identical suction levels in different positions lead to different stimuli at the carotid receptor. This interference has to be considered in microgravity studies by beat-by-beat measurement of cardiac output and blood pressure.

The effect of positive end-expiratory pressure on pulse pressure ...

African Journals Online (AJOL)

The effect of positive end-expiratory pressure on pulse pressure variation. FJ Smith, M Geyser, I Schreuder, PJ Becker. Abstract. Objectives: To determine the effect of different levels of positive end-expiratory pressure (PEEP) on pulse pressure variation (PPV). Design: An observational study. Setting: Operating theatres of a ...

On pressure: volume relations in hemodialysis

NARCIS (Netherlands)

E.H.Y. Ie (Eric)

2005-01-01

textabstractChapter 1 is a brief introduction to several aspects of cardiovascular pressure-volume relations in dialysis patients. The aims of the thesis are presented. In Chapter 2, an overview is presented of circulatory physiology in hemodialysis (HD) patients. Volume withdrawal by

Loading-unloading pressure-volume curves for rocks

International Nuclear Information System (INIS)

Stephens, D.R.; Lilley, E.M.

1970-01-01

The stress-strain codes (SOC and TENSOR) used to calculate phenomenology of nuclear explosion for the Plowshare Program require inter alia the pressure-volume relationships of the earth media. In this paper we describe a rapid and accurate method to obtain pressure-volume data to 40 kb at 25 deg. C for rocks. These experimental results may also be related to the in situ elastic properties of the rock and to other laboratory measurement of properties, such as ultrasonic experiments with pressure and Hugoniot determinations. Qualitative features of the pressure-volume curves can be related to the initial porosity of the rock. A porous rock is usually quite compressible at low pressures. If the porosity is in the form of narrow cracks, the cracks are closed at a pressure of about 3 to 6 kb, after which the rock is much less compressible. If the porosity is in the form of spherical pores, it is not necessarily removed even at pressures of 40 kb, depending on the strength of the rock, and the compressibility is higher at all pressures than for a similar rock containing no porosity. Data for water-saturated samples show the phase transformation due to free water at about 10 and 22 kb. However, the presence of 'nonliquid' water, which is loosely contained within the lattice of clay or zeolitic minerals or adsorbed on particle surfaces, is also observed. (author)

Loading-unloading pressure-volume curves for rocks

Energy Technology Data Exchange (ETDEWEB)

Stephens, D R; Lilley, E M [Lawrence Radiation Laboratory, University of California, Livermore, CA (United States)

1970-05-01

The stress-strain codes (SOC and TENSOR) used to calculate phenomenology of nuclear explosion for the Plowshare Program require inter alia the pressure-volume relationships of the earth media. In this paper we describe a rapid and accurate method to obtain pressure-volume data to 40 kb at 25 deg. C for rocks. These experimental results may also be related to the in situ elastic properties of the rock and to other laboratory measurement of properties, such as ultrasonic experiments with pressure and Hugoniot determinations. Qualitative features of the pressure-volume curves can be related to the initial porosity of the rock. A porous rock is usually quite compressible at low pressures. If the porosity is in the form of narrow cracks, the cracks are closed at a pressure of about 3 to 6 kb, after which the rock is much less compressible. If the porosity is in the form of spherical pores, it is not necessarily removed even at pressures of 40 kb, depending on the strength of the rock, and the compressibility is higher at all pressures than for a similar rock containing no porosity. Data for water-saturated samples show the phase transformation due to free water at about 10 and 22 kb. However, the presence of 'nonliquid' water, which is loosely contained within the lattice of clay or zeolitic minerals or adsorbed on particle surfaces, is also observed. (author)

Treatment of sleep-disordered breathing with positive airway pressure devices: technology update

Directory of Open Access Journals (Sweden)

Johnson KG

2015-10-01

Full Text Available Karin Gardner Johnson, Douglas Clark Johnson Department of Medicine, Baystate Medical Center, Springfield, MA, USA Abstract: Many types of positive airway pressure (PAP devices are used to treat sleep-disordered breathing including obstructive sleep apnea, central sleep apnea, and sleep-related hypoventilation. These include continuous PAP, autoadjusting CPAP, bilevel PAP, adaptive servoventilation, and volume-assured pressure support. Noninvasive PAP has significant leak by design, which these devices adjust for in different manners. Algorithms to provide pressure, detect events, and respond to events vary greatly between the types of devices, and vary among the same category between companies and different models by the same company. Many devices include features designed to improve effectiveness and patient comfort. Data collection systems can track compliance, pressure, leak, and efficacy. Understanding how each device works allows the clinician to better select the best device and settings for a given patient. This paper reviews PAP devices, including their algorithms, settings, and features. Keywords: BiPAP, CPAP, iVAPS, AVAPS, ASV, positive pressure respiration, instrumentation, treatment algorithm

The position of the arm during blood pressure measurement in sitting position.

Science.gov (United States)

Adiyaman, Ahmet; Verhoeff, Rutger; Lenders, Jacques W M; Deinum, Jaap; Thien, Theo

2006-12-01

Determining the influence of the position of the arm on blood pressure measurement in the sitting position. Blood pressure of 128 individuals (the majority being treated hypertensive patients) visiting the outpatient clinic was measured simultaneously on both arms with arms in two different positions. First, both arms were placed at the chair support level and blood pressure was measured three times on both arms after 10 min of rest. Subsequently, while still remaining in the same sitting position, five blood pressure measurements were made simultaneously at both arms with one arm placed on the desk and one arm placed and supported at heart level (mid-sternal). The arm placed at heart level served as the reference arm. The choice of which arm was placed at desk level and which arm was placed at heart level was randomized. Both at desk level and at chair support level, mean (+/-SD) systolic and diastolic blood pressures were higher than blood pressure at heart level by 6.1/5.7+/-4.6/3.1 and 9.3/9.4+/-5.4/3.4 mmHg, respectively. The effect of the height differences between the arm positions on the blood pressure readings was smaller than predicted (0.49 mmHg/cm systolic and 0.47 mmHg/cm diastolic). No significant correlation was found between blood pressure difference in the different arm positions (desk and heart level) and age, sex, weight or baseline blood pressure. Different arm positions below heart level have significant effects on blood pressure readings. The leading guidelines about arm position during blood pressure measurement are not in accordance with the arm position used in the Framingham study, the most frequently used study for risk estimations.

Right ventricular function during one-lung ventilation: effects of pressure-controlled and volume-controlled ventilation.

Science.gov (United States)

Al Shehri, Abdullah M; El-Tahan, Mohamed R; Al Metwally, Roshdi; Qutub, Hatem; El Ghoneimy, Yasser F; Regal, Mohamed A; Zien, Haytham

2014-08-01

To test the effects of pressure-controlled (PCV) and volume-controlled (VCV) ventilation during one-lung ventilation (OLV) for thoracic surgery on right ventricular (RV) function. A prospective, randomized, double-blind, controlled, crossover study. A single university hospital. Fourteen pairs of consecutive patients scheduled for elective thoracotomy. Patients were assigned randomly to ventilate the dependent lung with PCV or VCV mode, each in a randomized crossover order using tidal volume of 6 mL/kg, I: E ratio 1: 2.5, positive end-expiratory pressure (PEEP) of 5 cm H2O and respiratory rate adjusted to maintain normocapnia. Intraoperative changes in RV function (systolic and early diastolic tricuspid annular velocity (TAV), end-systolic volume (ESV), end-diastolic volume (EDV) and fractional area changes (FAC)), airway pressures, compliance and oxygenation index were recorded. The use of PCV during OLV resulted in faster systolic (10.1±2.39 vs. 5.8±1.67 cm/s, respectively), diastolic TAV (9.2±1.99 vs. 4.6±1.42 cm/s, respectively) (prights reserved.

Leakage Characteristics of Dual-Cannula Fenestrated Tracheostomy Tubes during Positive Pressure Ventilation: A Bench Study

Directory of Open Access Journals (Sweden)

Thomas Berlet

2016-01-01

Full Text Available This study compared the leakage characteristics of different types of dual-cannula fenestrated tracheostomy tubes during positive pressure ventilation. Fenestrated Portex® Blue Line Ultra®, TRACOE® twist, or Rüsch® Traceofix® tracheostomy tubes equipped with nonfenestrated inner cannulas were tested in a tracheostomy-lung simulator. Transfenestration pressures and transfenestration leakage rates were measured during positive pressure ventilation. The impact of different ventilation modes, airway pressures, temperatures, and simulated static lung compliance settings on leakage characteristics was assessed. We observed substantial differences in transfenestration pressures and transfenestration leakage rates. The leakage rates of the best performing tubes were <3.5% of the delivered minute volume. At body temperature, the leakage rates of these tracheostomy tubes were <1%. The tracheal tube design was the main factor that determined the leakage characteristics. Careful tracheostomy tube selection permits the use of fenestrated tracheostomy tubes in patients receiving positive pressure ventilation immediately after stoma formation and minimises the risk of complications caused by transfenestration gas leakage, for example, subcutaneous emphysema.

Non-invasive measurements of pulse pressure variation and stroke volume variation in anesthetized patients using the Nexfin blood pressure monitor.

Science.gov (United States)

Stens, Jurre; Oeben, Jeroen; Van Dusseldorp, Ab A; Boer, Christa

2016-10-01

Nexfin beat-to-beat arterial blood pressure monitoring enables continuous assessment of hemodynamic indices like cardiac index (CI), pulse pressure variation (PPV) and stroke volume variation (SVV) in the perioperative setting. In this study we investigated whether Nexfin adequately reflects alterations in these hemodynamic parameters during a provoked fluid shift in anesthetized and mechanically ventilated patients. The study included 54 patients undergoing non-thoracic surgery with positive pressure mechanical ventilation. The provoked fluid shift comprised 15° Trendelenburg positioning, and fluid responsiveness was defined as a concomitant increase in stroke volume (SV) >10 %. Nexfin blood pressure measurements were performed during supine steady state, Trendelenburg and supine repositioning. Hemodynamic parameters included arterial blood pressure (MAP), CI, PPV and SVV. Trendelenburg positioning did not affect MAP or CI, but induced a decrease in PPV and SVV by 3.3 ± 2.8 and 3.4 ± 2.7 %, respectively. PPV and SVV returned back to baseline values after repositioning of the patient to baseline. Bland-Altman analysis of SVV and PPV showed a bias of -0.3 ± 3.0 % with limits of agreement ranging from -5.6 to 6.2 %. The SVV was more superior in predicting fluid responsiveness (AUC 0.728) than the PVV (AUC 0.636), respectively. The median bias between PPV and SVV was different for patients younger [-1.5 % (-3 to 0)] or older [+2 % (0-4.75)] than 55 years (P < 0.001), while there were no gender differences in the bias between PPV and SVV. The Nexfin monitor adequately reflects alterations in PPV and SVV during a provoked fluid shift, but the level of agreement between PPV and SVV was low. The SVV tended to be superior over PPV or Eadyn in predicting fluid responsiveness in our population.

Respiratory System Mechanics During Low Versus High Positive End-Expiratory Pressure in Open Abdominal Surgery: A Substudy of PROVHILO Randomized Controlled Trial

NARCIS (Netherlands)

D'Antini, Davide; Huhle, Robert; Herrmann, Jacob; Sulemanji, Demet S.; Oto, Jun; Raimondo, Pasquale; Mirabella, Lucia; Hemmes, Sabrine N. T.; Schultz, Marcus J.; Pelosi, Paolo; Kaczka, David W.; Vidal Melo, Marcos Francisco; Gama de Abreu, Marcelo; Cinnella, Gilda

2018-01-01

In the 2014 PROtective Ventilation using HIgh versus LOw positive end-expiratory pressure (PROVHILO) trial, intraoperative low tidal volume ventilation with high positive end-expiratory pressure (PEEP = 12 cm H2O) and lung recruitment maneuvers did not decrease postoperative pulmonary complications

Recommended reference materials for realization of physicochemical properties pressure-volume-temperature relationships

CERN Document Server

Herington, E F G

1977-01-01

Recommended Reference Materials for Realization of Physicochemical Properties presents recommendations of reference materials for use in measurements involving physicochemical properties, namely, vapor pressure; liquid-vapor critical temperature and critical pressure; orthobaric volumes of liquid and vapor; pressure-volume-temperature properties of the unsaturated vapor or gas; and pressure-volume-temperature properties of the compressed liquid. This monograph focuses on reference materials for vapor pressures at temperatures up to 770 K, as well as critical temperatures and critical pressures

Peak systolic pressure-volume relationships in man

International Nuclear Information System (INIS)

Adachi, Haruhiko; Sugihara, Hiroki; Nakagawa, Hiroaki; Katsume, Hiroshi; Ochiai, Masakazu; Ijichi, Hamao

1985-01-01

We determined the relationship between left ventricular (LV) peak systolic pressure (PSP) and end-systolic volume, non-invasively using cuff sphygmomanometry and radionuclide angiocardiography (RNA). Systolic blood pressure (SBP) measured in the arm was substituted for PSP. LV enddiastolic volume (EDV), end-systolic volume (ESV) and ejection fraction (EF) were determined by a non-geometric method of gated RNA and recorded in three different hemodynamic states: at rest (basal state), during increased SBP after angiotensin administration (initial dose, 1-2 μg/min) and during decreased SBP after nitrate (sublingual nitroglycerin, 0.3-0.6 mg, or intravenous isosorbide dinitrate, 0.5-1.0 mg/min). The reproducibility of this method, tested in six subjects, proved to be good. Fifty-five subjects were divided into four groups based on EF at rest. The EDV and ESV were increased by angiotensin, and decreased by nitrate in all groups. EF was decreased by angiotensin and increased by nitrate. In contrast, the changes in PSP/ESVI due to these drugs remained in a narrow range in all groups. The regression lines of the PSP/ESVI relationship were almost linear and were steeper in the group with higher EF. Esub(max), the slope of the lines, was 5.75 +- 3.48 mmHg/ml/m 2 in group 1 (EF>50%), 3.16 +- 1.83 mmHg/ml/m 2 in group 2 (EF 49-40%), 2.27 +- 0.86 mmHg/ml/m 2 in group 3 (EF 39-30%) and 0.59 +- 0.50 mmHg/ml/m 2 in group 4 (EF<29%). The theoretical volume at zero pressure (VoI) did not meet in a definite value and was not related to EF at rest. Thus, the left ventricular peak systolic pressure-end-systolic volume relationship can be assessed non-invasively from radionuclide angiocardiography, which can be widely used for the evaluation of ventricular contractility, even in patients with asynergic ventricular contraction for whom echocardiography is unsuitable in measuring ventricular volume. (author)

Independent verification of tank volume measurements by pressure-volume authentication

International Nuclear Information System (INIS)

Suda, S.C.; Keisch, B.

1992-01-01

Brookhaven National Laboratory has developed a portable pressure-volume authenticator** as a standard and means of checking the functionality and quality of bubbler-probe volumetric devices. The pressure-volume authenticator (PVA) consists of an automated electromanometer system that is controlled by a laptop computer, and a transportable volumetric artifact. A portable pressure gage is connected, via a scanivalve, to the operator's bubbler-probe system and independently measures all bubbler probes. The transportable volumetric artifact is a one-meter high vessel equipped with bubble-probes, computer controlled air-purge rotameters, and platinum resistance (RTD) thermometer. High quality measurements are obtained by use of a fast sampling technique and sophisticated software developed under this program. The computer software performs the following functions: (a) instrument control, (b) data acquisition, (c) on-line graphical and numerical display of measurement data, and (d) detailed data analysis. The device also may provide hands-on training for inspectors and plant operators in high quality volumetric data collection and analysis. A field demonstration of the automated electromanometer system was conducted on the PETRA input accountancy tank, JRC-Ispra in November 1991

Treatment of sleep-disordered breathing with positive airway pressure devices: technology update.

Science.gov (United States)

Johnson, Karin Gardner; Johnson, Douglas Clark

2015-01-01

Many types of positive airway pressure (PAP) devices are used to treat sleep-disordered breathing including obstructive sleep apnea, central sleep apnea, and sleep-related hypoventilation. These include continuous PAP, autoadjusting CPAP, bilevel PAP, adaptive servoventilation, and volume-assured pressure support. Noninvasive PAP has significant leak by design, which these devices adjust for in different manners. Algorithms to provide pressure, detect events, and respond to events vary greatly between the types of devices, and vary among the same category between companies and different models by the same company. Many devices include features designed to improve effectiveness and patient comfort. Data collection systems can track compliance, pressure, leak, and efficacy. Understanding how each device works allows the clinician to better select the best device and settings for a given patient. This paper reviews PAP devices, including their algorithms, settings, and features.

Fuzzy Control of Tidal volume, Respiration number and Pressure value

OpenAIRE

Hasan Guler; Fikret Ata

2010-01-01

In this study, control of tidal volume, respiration number and pressure value which are arrived to patient at mechanical ventilator device which is used in intensive care units were performed with fuzzy logic controller. The aim of this system is to reduce workload of aneshesiologist. By calculating tidal volume, respiration number and pressure value, the error Pe(k) between reference pressure value (Pref) and pressure of gas given ill person (Phasta) and error change rate ;#948;Pe(k) were co...

Three-Dimensional Echocardiography-Derived Non-Invasive Right Ventricular Pressure-Volume Analysis.

Science.gov (United States)

Huang, Kuan-Chih; Lin, Lian-Yu; Hwang, Juey-Jen; Lin, Lung-Chun

2017-09-01

In patients with pulmonary hypertension, repeated evaluations of right ventricular (RV) function are still required for clinical decision making, but the invasive nature of current pressure-volume analysis makes conducting regular follow-ups in a clinical setting infeasible. We enrolled 12 patients with pulmonary arterial hypertension (PAH) and 10 with pulmonary venous hypertension (PVH) May 2016-October 2016. All patients underwent a clinically indicated right heart catheterization (RHC), from which the yielded right ventricular pressure recordings were conjugated with RV volume by 3-D echocardiography to generate a pressure-volume loop. A continuous-wave Doppler envelope of tricuspid regurgitation was transformed into a pressure gradient recording by the simplified Bernoulli equation, and then a systolic pressure gradient-volume (PG-V) diagram was generated from similar methods. The area enclosed by the pressure-volume loop was calculated to represent semi-invasive right ventricular stroke work (RVSW RHC ). The area between the PG-V diagram and x-axis was calculated to estimate non-invasive RVSW (RVSW echo ). Patients with PAH have higher RV pressure, lower pulmonary arterial wedge pressure and larger RV volume that was contributed by the dilation of RV mid-cavity minor dimension. We found no significant difference of traditional parameters between these two groups, but RVSW values were significantly higher in PAH patients. The RVSW values of these two methods were significantly correlated by the equation RVSW echo  = 0.8447 RVSW RHC  + 129.38 (R 2  = 0.9151, p rights reserved.

Intrinsic positive end-expiratory pressure during one-lung ventilation of patients with pulmonary hyperinflation. Influence of low respiratory rate with unchanged minute volume.

Science.gov (United States)

Szegedi, L L; Barvais, L; Sokolow, Y; Yernault, J C; d'Hollander, A A

2002-01-01

We measured lung mechanics and gas exchange during one-lung ventilation (OLV) of patients with chronic obstructive pulmonary disease, using three respiratory rates (RR) and unchanged minute volume. We studied 15 patients about to undergo lung surgery, during anaesthesia, and placed in the lateral position. Ventilation was with constant minute volume, inspiratory flow and FIO2. For periods of 15 min, RR of 5, 10, and 15 bpm were applied in a random sequence and recordings were made of lung mechanics and an arterial blood gas sample was taken. Data were analysed with the repeated measures ANOVA and paired t-test with Bonferroni correction. PaO2 changes were not significant. At the lowest RR, PaCO2 decreased (from 42 (SD 4) mm Hg at RR 15-41 (4) mm Hg at RR 10 and 39 (4) mm Hg at RR 5, P<0.01), and end-tidal carbon dioxide increased (from 33 (5) mm Hg at RR 15 to 35 (5) mm Hg at RR 10 and 36 (6) mm Hg at RR 5, P<0.01). Intrinsic positive end-expiratory pressure (PEEPi) was reduced even with larger tidal volumes (from 6 (4) cm H2O at RR 15-5 (4) cm H2O at RR 10, and 3 (3) cm H2O at RR 5, P<0.01), most probably caused by increased expiratory time at the lowest RR. A reduction in RR reduces PEEPi and hypercapnia during OLV in anaesthetized patients with chronic obstructive lung disease.

The deflation limb of the pressure-volume relationship in infants during high-frequency ventilation.

Science.gov (United States)

Tingay, David G; Mills, John F; Morley, Colin J; Pellicano, Anastasia; Dargaville, Peter A

2006-02-15

The importance of applying high-frequency oscillatory ventilation with a high lung volume strategy in infants is well established. Currently, a lack of reliable methods for assessing lung volume limits clinicians' ability to achieve the optimum volume range. To map the pressure-volume relationship of the lung during high-frequency oscillatory ventilation in infants, to determine at what point ventilation is being applied clinically, and to describe the relationship between airway pressure, lung volume, and oxygenation. In 12 infants, a partial inflation limb and the deflation limb of the pressure-volume relationship were mapped using a quasi-static lung volume optimization maneuver. This involved stepwise airway pressure increments to total lung capacity, followed by decrements until the closing pressure of the lung was identified. Lung volume and oxygen saturation were recorded at each airway pressure. Lung volume was measured using respiratory inductive plethysmography. A distinct deflation limb could be mapped in each infant. Overall, oxygenation and lung volume were improved by applying ventilation on the deflation limb. Maximal lung volume and oxygenation occurred on the deflation limb at a mean airway pressure of 3 and 5 cm H(2)O below the airway pressure approximating total lung capacity, respectively. Using current ventilation strategies, all infants were being ventilated near the inflation limb. It is possible to delineate the deflation limb in infants receiving high-frequency oscillatory ventilation; in doing so, greater lung volume and oxygenation can be achieved, often at lower airway pressures.

Real-time display of flow-pressure-volume loops.

Science.gov (United States)

Morozoff, P E; Evans, R W

1992-01-01

Graphic display of respiratory waveforms can be valuable for monitoring the progress of ventilated patients. A system has been developed that can display flow-pressure-volume loops as derived from a patient's respiratory circuit in real time. It can also display, store, print, and retrieve ventilatory waveforms. Five loops can be displayed at once: current, previous, reference, "ideal," and previously saved. Two components, the data-display device (DDD) and the data-collection device (DCD), comprise the system. An IBM 286/386 computer with a graphics card (VGA) and bidirectional parallel port is used for the DDD; an eight-bit microprocessor card and an A/D convertor card make up the DCD. A real-time multitasking operating system was written to control the DDD, while the DCD operates from in-line assembly code. The DCD samples the pressure and flow sensors at 100 Hz and looks for a complete flow waveform pattern based on flow slope. These waveforms are then passed to the DDD via the mutual parallel port. Within the DDD a process integrates the flow to create a volume signal and performs a multilinear regression on the pressure, flow, and volume data to calculate the elastance, resistance, pressure offset, and coefficient of determination. Elastance, resistance, and offset are used to calculate Pr and Pc where: Pr[k] = P[k]-offset-(elastance.V[k]) and Pc[k] = P[k]-offset-(resistance.F[k]). Volume vs. Pc and flow vs. Pr can be displayed in real time. Patient data from previous clinical tests were loaded into the device to verify the software calculations. An analog waveform generator was used to simulate flow and pressure waveforms that validated the system.(ABSTRACT TRUNCATED AT 250 WORDS)

The position of the arm during blood pressure measurement in sitting position.

NARCIS (Netherlands)

Adiyaman, A.; Verhoeff, R.; Lenders, J.W.M.; Deinum, J.; Thien, Th.

2006-01-01

OBJECTIVE: Determining the influence of the position of the arm on blood pressure measurement in the sitting position. METHODS: Blood pressure of 128 individuals (the majority being treated hypertensive patients) visiting the outpatient clinic was measured simultaneously on both arms with arms in

A comparison between the dimensions of positive transtibial residual limb molds prepared by air pressure casting and weight-bearing casting methods.

Science.gov (United States)

Hajiaghaei, Behnam; Ebrahimi, Ismail; Kamyab, Mojtaba; Saeedi, Hassan; Jalali, Maryam

2016-01-01

Creating a socket with proper fit is an important factor to ensure the comfort and control of prosthetic devices. Several techniques are commonly used to cast transtibial stumps but their effect on stump shape deformation is not well understood. This study compares the dimensions, circumferences and volumes of the positive casts and also the socket comfort between two casting methods. Our hypothesis was that the casts prepared by air pressure method have less volume and are more comfortable than those prepared by weight bearing method. Fifteen transtibial unilateral amputees participated in the study. Two weight bearing and air pressure casting methods were utilized for their residual limbs. The diameters and circumferences of various areas of the residual limbs and positive casts were compared. The volumes of two types of casts were measured by a volumeter and compared. Visual Analogue Scale (VAS) was used to measure the sockets fit comfort. Circumferences at 10 and 15 cm below the patella on the casts were significantly smaller in air pressure casting method compared to the weight bearing method (p=0.00 and 0.01 respectively). The volume of the cast in air pressure method was lower than that of the weight bearing method (p=0.006). The amputees found the fit of the sockets prepared by air pressure method more comfortable than the weight bearing sockets (p=0.015). The air pressure casting reduced the circumferences of the distal portion of residual limbs which has more soft tissue and because of its snug fit it provided more comfort for amputees, according to the VAS measurements.

Apparatus to measure vapor pressure, differential vapor pressure, liquid molar volume, and compressibility of liquids and solutions to the critical point. Vapor pressures, molar volumes, and compressibilities of protiobenzene and deuteriobenzene at elevated temperatures

International Nuclear Information System (INIS)

Kooner, Z.S.; Van Hook, W.A.

1986-01-01

An apparatus designed to measure vapor pressure differences between two similar liquids, such as isotopic isomers, or between a solution and its reference solvent at temperatures and pressures extending to the critical point is described. Vapor-phase volume is minimized and pressure is transmitted to the transducer through the liquid, thereby avoiding several experimental difficulties. Liquid can be injected into the heated part of the system by volumetrically calibrated screw injectors, thus permitting measurements of liquid molar volume, compressibility, and expansivity. The addition of a high-pressure circulating pump and injection valve allows the apparatus to be employed as a continuous dilution differential vapor pressure apparatus for determining partial molar free energies of solution. In the second part of the paper data on the vapor pressure, molar volume, compressibility, and expansivity and their isotope effects for C 6 H 6 and C 6 D 6 from room temperature to near the critical temperature are reported

The decrease of cardiac chamber volumes and output during positive-pressure ventilation

DEFF Research Database (Denmark)

Kristensen, Kasper Kyhl; Ahtarovski, Kiril Aleksov; Iversen, Kasper

2013-01-01

the effect of PPV on the central circulation by studying cardiac chamber volumes with cardiac magnetic resonance imaging (CMR). We hypothesized that PPV lowers cardiac output (CO) mainly via the Frank-Starling relationship. In 18 healthy volunteers, cardiac chamber volumes and flow in aorta and the pulmonary...... artery were measured by CMR during PPV levels of 0, 10, and 20 cmH2O applied via a respirator and a face mask. All cardiac chamber volumes decreased in proportion to the level of PPV. Following 20-cmH2O PPV, the total diastolic and systolic cardiac volumes (±SE) decreased from 605 (±29) ml to 446 (±29......) ml (P volume decreased by 27 (±4) ml/beat; heart rate increased by 7 (±2) beats/min; and CO decreased by 1.0 (±0.4) l/min (P

Comparison of Efficacy and Tolerance of Automatic Continuous Positive Airway Pressure Devices With the Optimum Continuous Positive Airway Pressure.

Science.gov (United States)

Tommi, George; Aronow, Wilbert S; Sheehan, John C; McCleay, Matthew T; Meyers, Patrick G

Patients diagnosed with obstructive sleep apnea syndrome were randomly placed on automatic continuous positive airway pressure (ACPAP) for 2 hours followed by manual titration for the rest of the night. One hundred sixty-one patients entered the study, with at least 50 patients titrated with each of 3 ACPAP devices. The optimum continuous positive airway pressure (CPAP) was defined as the lowest pressure with an apnea-hypoxia index of ≤5/hr, which ranged from 4 cm to 18 cm. Success with ACPAP was approximately 60%-80% when the optimum CPAP was 4-6 cm but fell to below 30% if the optimum CPAP was ≥8 cm (P = 0.001). Average ACPAP ranged from 2 to 10 cm below the optimum level if the optimum CPAP was ≥8 cm. Patients who responded to a low CPAP but deteriorated on higher pressures failed to respond to any of the automatic devices. We recommend that CPAP titration be performed manually before initiation of ACPAP in patients with obstructive sleep apnea. The basal pressure for ACPAP should be the optimum pressure obtained by manual titration. Limits on the upper level of ACPAP may be necessary for patients who deteriorate on higher positive pressures.

Bulk-volume behavior of pressure-densified amorphous polymers and free-volume behavior by positron annihilation lifetime measurement

International Nuclear Information System (INIS)

Hagiwara, K.; Ougizawa, T.; Inoue, T.; Hirata, K.; Kobayashi, Y.

2001-01-01

In order to study the nature of amorphous polymers, the free volume contribution on the bulk volume change was investigated on the basis of the relationship between the bulk volume behavior by PVT (pressure-volume-temperature) measurement and the free volume behavior by PALS (positron annihilation lifetime spectroscopy) measurement. A densified glass, prepared by cooling at constant rate from the melt state temperature to room temperature under 200 MPa, showed smaller bulk volume and free volume than non-densified glass. And the densified glass showed not only the same glass transition temperature (Tg) as non-densified glass but also another transition at lower temperature around (Tg-30 C). In this glass-glass transition, both the bulk volume and free volume of densified glass recovered to those of non-densified glass. Moreover the densified glass showed different thermal behavior from the glass which was enthalpy-relaxed under atmospheric pressure. From those results, it was considered that the free volume behavior largely related to the behavior of amorphous polymers. (orig.)

Influence of Head and Neck Position on Oropharyngeal Leak Pressure and Cuff Position with the ProSeal Laryngeal Mask Airway and the I-Gel: A Randomized Clinical Trial

Directory of Open Access Journals (Sweden)

Sandeep Kumar Mishra

2015-01-01

Full Text Available Background. This study was designed to assess and compare the effect of head and neck position on the oropharyngeal leak pressures and cuff position (employing fibreoptic view of the glottis and ventilation scores between ProSeal LMA and the I-gel. Material and Methods. After induction of anesthesia, the supraglottic device was inserted and ventilation confirmed. The position of the head was randomly changed from neutral to flexion, extension, and lateral rotation (left. The oropharyngeal leak pressures, fibreoptic view of glottis, ventilation scores, and delivered tidal volumes and end tidal CO2 were noted in all positions. Results. In both groups compared with neutral position, oropharyngeal leak pressures were significantly higher with flexion and lower with extension but similar with rotation of head and neck. However the oropharyngeal leak pressure was significantly higher for ProSeal LMA compared with the I-gel in all positions. Peak airway pressures were significantly higher with flexion in both groups (however this did not affect ventilation, lower with extension in ProSeal group, and comparable in I-gel group but did not change significantly with rotation of head and neck in both groups. Conclusion. Effective ventilation can be done with both ProSeal LMA and I-gel with head in all the above positions. ProSeal LMA has a better margin of safety than I-gel due to better sealing pressures except in flexion where the increase in airway pressure is more with the former. Extreme precaution should be taken in flexion position in ProSeal LMA.

Cerebral blood volume changes in cats with acute increased intracranial pressure

International Nuclear Information System (INIS)

Kondo, Takashi; Kano, Mitsumasa; Ikeda, Takuya.

1984-01-01

We measured the changes in cerebral blood volume in cats with increased intracranial pressure with a high-speed CT scanner, employing contrast effects by the iodine agent. In acute increased intracranial pressure caused by raising the extradural pressure by 20 mmHg, cerebral blood volume showed a significant decrease by 32% in comparison with that at normal intracranial pressure. There was also a tendency that a decline of iodine was delayed with time at increased intracranial pressure than that at normal pressure. This was supposed to be a delay of cerebral circulation due to venous congestion. This experimental model and measuring method provide the changes in CBV in the same individual without any tedious procedure, and therefore this is a reliable method with respect to precision. (author)

Intraoperative protective mechanical ventilation for prevention of postoperative pulmonary complications: a comprehensive review of the role of tidal volume, positive end-expiratory pressure, and lung recruitment maneuvers.

Science.gov (United States)

Güldner, Andreas; Kiss, Thomas; Serpa Neto, Ary; Hemmes, Sabrine N T; Canet, Jaume; Spieth, Peter M; Rocco, Patricia R M; Schultz, Marcus J; Pelosi, Paolo; Gama de Abreu, Marcelo

2015-09-01

Postoperative pulmonary complications are associated with increased morbidity, length of hospital stay, and mortality after major surgery. Intraoperative lung-protective mechanical ventilation has the potential to reduce the incidence of postoperative pulmonary complications. This review discusses the relevant literature on definition and methods to predict the occurrence of postoperative pulmonary complication, the pathophysiology of ventilator-induced lung injury with emphasis on the noninjured lung, and protective ventilation strategies, including the respective roles of tidal volumes, positive end-expiratory pressure, and recruitment maneuvers. The authors propose an algorithm for protective intraoperative mechanical ventilation based on evidence from recent randomized controlled trials.

Pressure Dependence of Molar Volume near the Melting Point in Benzene

Institute of Scientific and Technical Information of China (English)

无

2007-01-01

The pressure dependence of the molar volume was at constant temperatures close to the melting point in benzene. The molar volume of benzene was calculated using experimental data for the thermal expansivity for constant temperatures of 25℃, 28.5℃, 40℃, and 51℃ at various pressures for both the solid and liquid phases. The predictions are in good agreement with the observed volumes in both the solid and liquid phases of benzene. The predicted values of the molar volume for a constant temperature of 28.5℃ in the liquid phase of benzene agree well with experimental data in the literature.

Extubation success in premature infants with respiratory distress syndrome treated with bi-level nasal continuous positive airway pressure versus nasal intermittent positive pressure ventilation.

Science.gov (United States)

Thomas, Patricia E; LeFlore, Judy

2013-01-01

Infants born prematurely with respiratory distress syndrome are at high risk for complications from mechanical ventilation. Strategies are needed to minimize their days on the ventilator. The purpose of this study was to compare extubation success rates in infants treated with 2 different types of continuous positive airway pressure devices. A retrospective cohort study design was used. Data were retrieved from electronic medical records for patients in a large, metropolitan, level III neonatal intensive care unit. A sample of 194 premature infants with respiratory distress syndrome was selected, 124 of whom were treated with nasal intermittent positive pressure ventilation and 70 with bi-level variable flow nasal continuous positive airway pressure (bi-level nasal continuous positive airway pressure). Infants in both groups had high extubation success rates (79% of nasal intermittent positive pressure ventilation group and 77% of bi-level nasal continuous positive airway pressure group). Although infants in the bi-level nasal continuous positive airway pressure group were extubated sooner, there was no difference in duration of oxygen therapy between the 2 groups. Promoting early extubation and extubation success is a vital strategy to reduce complications of mechanical ventilation that adversely affect premature infants with respiratory distress syndrome.

Experimental Pressure-Volume diagrams of scroll compressors

OpenAIRE

Picavet, Alain; Ginies, Pierre

2014-01-01

This paper presents the results of tests led with scroll compressors to establish pressure-volume diagrams. Two compressors were thinly instrumented with pressure and displacement sensors so as to follow the whole compression process, from suction to exhaust. A gear coder was set to mark off the closing and opening of gas pockets, and to study the speed variations occurring during a single rotation. These tests help to understand the various phenomena met in a compressor, such as back-flow, o...

Left ventricular pressure and volume data acquisition and analysis using LabVIEW.

Science.gov (United States)

Cassidy, S C; Teitel, D F

1997-03-01

To automate analysis of left ventricular pressure-volume data, we used LabVIEW to create applications that digitize and display data recorded from conductance and manometric catheters. Applications separate data into cardiac cycles, calculate parallel conductance, and calculate indices of left ventricular function, including end-systolic elastance, preload-recruitable stroke work, stroke volume, ejection fraction, stroke work, maximum and minimum derivative of ventricular pressure, heart rate, indices of relaxation, peak filling rate, and ventricular chamber stiffness. Pressure-volume loops can be graphically displayed. These analyses are exported to a text-file. These applications have simplified and automated the process of evaluating ventricular function.

(Pressure + volume + temperature) properties for binary oligomeric solutions of poly(ethylene glycol mono-4-octylphenyl ether) with 1-octanol or acetophenone at pressures up to 50 MPa

International Nuclear Information System (INIS)

Lee, M.-J.; Ku, T.-J.; Lin Homu

2009-01-01

Densities were measured with a high-pressure densitometer for two binary oligomeric systems of poly(ethylene glycol mono-4-octylphenyl ether) (PEGOPE) with 1-octanol or acetophenone at temperatures from 298.15 K to 348.15 K and pressures up to 50 MPa. While the excess volumes are negative in (acetophenone + PEGOPE) over the entire composition range, those are found to change from positive to negative with increasing mole fraction of the solvent in (1-octanol + PEGOPE). The pressure-effect on the liquid densities can be represented accurately by the Tait equation. Moreover, an empirical equation with two characteristic parameters correlates well the PVT data over the entire experimental conditions for each binary system. The experimental specific volumes were also correlated with the Flory-Orwoll-Vrij (FOV) and the Schotte equations of state to within the experimental uncertainty.

Reverse Trendelenburg position is a safer technique for lowering central venous pressure without decreasing blood pressure than clamping of the inferior vena cava below the liver.

Science.gov (United States)

Yoneda, Godai; Katagiri, Satoshi; Yamamoto, Masakazu

2015-06-01

Bleeding remains an important intraoperative complication in patients who undergo hepatectomy. It is generally believed that a reduction in central venous pressure will decrease bleeding from the hepatic venous system. To our knowledge, however, no study has compared the effectiveness of these techniques for controlling bleeding. So we compared the effectiveness of central venous pressure control techniques, such as infrahepatic inferior vena cava clamping, changes in surgical position of the patient, and hypoventilation anesthesia, for lowering central venous pressure. The study group comprised 50 patients who underwent hepatectomy in our department from 2012 through 2013. A central venous catheter was inserted into the right internal jugular vein, and the tip was placed in the superior vena cava. A transducer was placed along the mid-axillary line of the left side of the chest. After opening the abdomen, changes in central venous pressure were measured during inferior vena cava clamping, the reverse Trendelenburg position, the Trendelenburg position, and hypoventilation anesthesia. The inclination relative to the transducer, as measured with an inclinometer, was -10 degrees for the Trendelenburg position and +10 degrees for the reverse Trendelenburg position. The tidal volume was set at 10 mL/kg during conventional anesthesia and 5 mL/kg during hypoventilation anesthesia. The mean central venous pressure was 8.0 cm H(2)O in the supine position during conventional anesthesia, 5.0 cm H(2)O during inferior vena cava clamping, 5.6 cm H(2)O during reverse Trendelenburg position, 10.6 cm H(2)O during Trendelenburg position, and 7.6 cm H(2)O during hypoventilation anesthesia. The mean central venous pressure during inferior vena cava clamping and reverse Trendelenburg position was significantly lower than that during supine position (P = 0.0017 and P = 0.0231, respectively). The mean central venous pressure during hypoventilation

Evaluation of a continuous-positive pressure generating system

Directory of Open Access Journals (Sweden)

Herrera N

2016-03-01

Full Text Available Nestor Herrera,1,2 Roberto Regnícoli,1,2 Mariel Murad1,2 1Neonatology Unit, Italian Hospital Garibaldi, Rosario, Argentina; 2Experimental Medicine and Surgery Unit, Italian University Institute of Rosario, Argentina Abstract: The use of systems that apply continuous-positive airway pressure by means of noninvasive methods is widespread in the neonatal care practice and has been associated with a decrease in the use of invasive mechanical ventilation, less administration of exogenous surfactant, and bronchopulmonary dysplasia. Few experimental studies on the functioning of the neonatology systems that generate continuous-positive airway pressure have been reported. A flow resistor system associated with an underwater seal resistor in a lung test model was described, and it was compared with an underwater seal threshold resistor system. Important differences in the pressures generated in the different systems studied were verified. The generation of pressure was associated with the immersion depth and the diameter of the bubble tubing. The flow resistor associated with an underwater seal, with small bubble tubing, showed no important differences in the evaluated pressures, exerting a stabilizing effect on the generated pressures. The importance of measuring the pressure generated by the different systems studied was verified, due to the differences between the working pressures set and the pressures measured. Keywords: continuous-positive pressure, flow and threshold resistor, BCPAP

Positive expiratory pressure - Common clinical applications and physiological effects.

Science.gov (United States)

Fagevik Olsén, Monika; Lannefors, Louise; Westerdahl, Elisabeth

2015-03-01

Breathing out against resistance, in order to achieve positive expiratory pressure (PEP), is applied by many patient groups. Pursed lips breathing and a variety of devices can be used to create the resistance giving the increased expiratory pressure. Effects on pulmonary outcomes have been discussed in several publications, but the expected underlying physiology of the effect is seldom discussed. The aim of this article is to describe the purpose, performance, clinical application and underlying physiology of PEP when it is used to increase lung volumes, decrease hyperinflation or improve airway clearance. In clinical practice, the instruction how to use an expiratory resistance is of major importance since it varies. Different breathing patterns during PEP increase or reduce expiratory flow, result in movement of EPP centrally or peripherally and can increase or decrease lung volume. It is therefore necessary to give the right instructions to obtain the desired effects. As the different PEP techniques are being used by diverse patient groups it is not possible to give standard instructions. Based on the information given in this article the instructions have to be adjusted to give the optimal effect. There is no consensus regarding optimal treatment frequency and number of cycles included in each treatment session and must also be individualized. In future research, more precise descriptions are needed about physiological aims and specific instructions of how the treatments have been performed to assure as good treatment quality as possible and to be able to evaluate and compare treatment effects. Copyright © 2014 Elsevier Ltd. All rights reserved.

Pressure-volume Relationship in the Stress-echocardiography Laboratory: Does (Left Ventricular End-diastolic) Size Matter?

Science.gov (United States)

Bombardini, Tonino; Mulieri, Louis A; Salvadori, Stefano; Costantino, Marco Fabio; Scali, Maria Chiara; Marzilli, Mario; Picano, Eugenio

2017-02-01

The variation between rest and peak stress end-systolic pressure-volume relation is an afterload-independent index of left ventricular contractility. Whether and to what extent it depends on end-diastolic volume remains unclear. The aim of this study was to assess the dependence of the delta rest-stress end-systolic pressure-volume relation on end-diastolic volume in patients with negative stress echo and all ranges of resting left ventricular function. We analyzed interpretable data obtained in 891 patients (593 men, age 63 ± 12 years) with ejection fraction 47% ± 12%: 338 were normal or near-normal or hypertensive; 229 patients had coronary artery disease; and 324 patients had ischemic or nonischemic dilated cardiomyopathy. They were studied with exercise (n = 172), dipyridamole (n = 482) or dobutamine (n = 237) stress echocardiography. The end-systolic pressure-volume relation was evaluated at rest and peak stress from raw measurement of systolic arterial pressure by cuff sphygmomanometer and end-systolic volume by biplane Simpson rule 2-dimensional echocardiography. Absolute values of delta rest-stress end-systolic pressure-volume relation were higher for exercise and dobutamine than for dipyridamole. In the overall population, an inverse relationship between end-systolic pressure-volume relation and end-diastolic volume was present at rest (r 2 = 0.69, P stress (r 2 = 0.56, P stress end-systolic pressure-volume relation was considered (r 2 = 0.13). Left ventricular end-diastolic volume does not affect the rest-stress changes in end-systolic pressure-volume relation in either normal or abnormal left ventricles during physical or pharmacological stress. Copyright © 2016 Sociedad Española de Cardiología. Published by Elsevier España, S.L.U. All rights reserved.

Cardiovascular regulation during body unweighting by lower body positive pressure.

Science.gov (United States)

Evans, Joyce M; Mohney, Lindsay; Wang, Siqi; Moore, Rachel K; Elayi, Samy-Claude; Stenger, Michael B; Moore, Fritz B; Knapp, Charles F

2013-11-01

We hypothesized that human cardiovascular responses to standing in reduced gravity environments, as on the Moon or Mars, could be modeled using a lower body positive pressure (LBPP) chamber. Heart rate, blood pressure, body segment fluid shifts, ECG, indexes of sympathetic, parasympathetic balance, and baroreflex control of the heart and periphery plus echocardiographic measures of cardiac function were recorded from seven men and seven women supine and standing at 100% (Earth), 40% (-Mars), and 20% (-Moon) bodyweights (BW). The fluid shifted from the chest was greater when standing at 100% BW than at 20% and 40% BW, while fluid pooled in the abdomen was similar at all BWs. Compared to moving from supine to standing at 100% BW, moving to 20% and 40% BW resulted in smaller decreases in stroke volume and pulse pressure, smaller increases in heart rate and smaller decreases in parasympathetic control of heart rate, baroreflex slope, numbers of blood pressure ramps, and much reduced indexes of sympathetic drive to the heart and periphery. However, peripheral vascular resistance, systolic pressure, and baroreflex effectiveness were elevated during 20% and 40% BW, compared to supine and standing at 100% BW. Standing at reduced bodyweight suppressed indexes of sympathetic control of heart rate and peripheral vasomotion. Regulatory responses indicated a combination of arterial and cardiopulmonary baroreflex control: mean heart rate, vasomotion, and baroreflex sensitivity appeared to be more under cardiopulmonary control while baroreflex effectiveness appeared to be driven more by the arterial baroreflex.

Differential effects of lower body negative pressure and upright tilt on splanchnic blood volume

Science.gov (United States)

Taneja, Indu; Moran, Christopher; Medow, Marvin S.; Glover, June L.; Montgomery, Leslie D.; Stewart, Julian M.

2015-01-01

Upright posture and lower body negative pressure (LBNP) both induce reductions in central blood volume. However, regional circulatory responses to postural changes and LBNP may differ. Therefore, we studied regional blood flow and blood volume changes in 10 healthy subjects undergoing graded lower-body negative pressure (−10 to −50 mmHg) and 8 subjects undergoing incremental head-up tilt (HUT; 20°, 40°, and 70°) on separate days. We continuously measured blood pressure (BP), heart rate, and regional blood volumes and blood flows in the thoracic, splanchnic, pelvic, and leg segments by impedance plethysmography and calculated regional arterial resistances. Neither LBNP nor HUT altered systolic BP, whereas pulse pressure decreased significantly. Blood flow decreased in all segments, whereas peripheral resistances uniformly and significantly increased with both HUT and LBNP. Thoracic volume decreased while pelvic and leg volumes increased with HUT and LBNP. However, splanchnic volume changes were directionally opposite with stepwise decreases in splanchnic volume with LBNP and stepwise increases in splanchnic volume during HUT. Splanchnic emptying in LBNP models regional vascular changes during hemorrhage. Splanchnic filling may limit the ability of the splanchnic bed to respond to thoracic hypovolemia during upright posture. PMID:17085534

Hemodynamic responses to external counterbalancing of auto-positive end-expiratory pressure in mechanically ventilated patients with chronic obstructive pulmonary disease.

Science.gov (United States)

Baigorri, F; de Monte, A; Blanch, L; Fernández, R; Vallés, J; Mestre, J; Saura, P; Artigas, A

1994-11-01

To study the effect of positive end-expiratory pressure (PEEP) on right ventricular hemodynamics and ejection fraction in patients with chronic obstructive pulmonary disease and positive alveolar pressure throughout expiration by dynamic hyperinflation (auto-PEEP). Open, prospective, controlled trial. General intensive care unit of a community hospital. Ten patients sedated and paralyzed with an acute exacerbation of chronic obstructive pulmonary disease undergoing mechanical ventilation. Insertion of a pulmonary artery catheter modified with a rapid response thermistor and a radial arterial catheter. PEEP was then increased from 0 (PEEP 0) to auto-PEEP level (PEEP = auto-PEEP) and 5 cm H2O above that (PEEP = auto-PEEP +5). At each level of PEEP, airway pressures, flow and volume, hemodynamic variables (including right ventricular ejection fraction by thermodilution technique), and blood gas analyses were recorded. The mean auto-PEEP was 6.6 +/- 2.8 cm H2O and the total PEEP reached was 12.2 +/- 2.4 cm H2O. The degree of lung inflation induced by PEEP averaged 145 +/- 87 mL with PEEP = auto-PEEP and 495 +/- 133 mL with PEEP = auto-PEEP + 5. The PEEP = auto-PEEP caused a right ventricular end-diastolic pressure increase, but there was no other significant hemodynamic change. With PEEP = auto-PEEP + 5, there was a significant increase in intravascular pressures; this amount of PEEP reduced cardiac output (from 4.40 +/- 1.38 L/min at PEEP 0 to 4.13 +/- 1.48 L/min; p 10% in only five cases and this group of patients had significantly lower right ventricular volumes than the group with less cardiac output variation (right ventricular end-diastolic volume: 64 +/- 9 vs. 96 +/- 26 mL/m2; right ventricular end-systolic volume: 38 +/- 6 vs. 65 +/- 21 mL/m2; p < .05) without significant difference in the other variables that were measured. Neither right ventricular ejection fraction nor right ventricle volumes changed as PEEP increased, but there were marked interpatient

Epicardial left ventricular lead placement for cardiac resynchronization therapy: optimal pace site selection with pressure-volume loops.

Science.gov (United States)

Dekker, A L A J; Phelps, B; Dijkman, B; van der Nagel, T; van der Veen, F H; Geskes, G G; Maessen, J G

2004-06-01

Patients in heart failure with left bundle branch block benefit from cardiac resynchronization therapy. Usually the left ventricular pacing lead is placed by coronary sinus catheterization; however, this procedure is not always successful, and patients may be referred for surgical epicardial lead placement. The objective of this study was to develop a method to guide epicardial lead placement in cardiac resynchronization therapy. Eleven patients in heart failure who were eligible for cardiac resynchronization therapy were referred for surgery because of failed coronary sinus left ventricular lead implantation. Minithoracotomy or thoracoscopy was performed, and a temporary epicardial electrode was used for biventricular pacing at various sites on the left ventricle. Pressure-volume loops with the conductance catheter were used to select the best site for each individual patient. Relative to the baseline situation, biventricular pacing with an optimal left ventricular lead position significantly increased stroke volume (+39%, P =.01), maximal left ventricular pressure derivative (+20%, P =.02), ejection fraction (+30%, P =.007), and stroke work (+66%, P =.006) and reduced end-systolic volume (-6%, P =.04). In contrast, biventricular pacing at a suboptimal site did not significantly change left ventricular function and even worsened it in some cases. To optimize cardiac resynchronization therapy with epicardial leads, mapping to determine the best pace site is a prerequisite. Pressure-volume loops offer real-time guidance for targeting epicardial lead placement during minimal invasive surgery.

Mechanical energy yields and pressure volume and pressure time curves for whole core fuel-coolant interactions

Energy Technology Data Exchange (ETDEWEB)

Coddington, P [United Kingdom Atomic Energy Authority, Atomic Energy Establishment, Winfrith, Dorchester, Dorset (United Kingdom)

1979-10-15

In determining the damage consequences of a whole core Fuel-Coolant Interaction (FCI), one measure of the strength of a FCI that can be used and is independent of the system geometry is the constant volume mixing mechanical yield (often referred to as the Hicks-Menzies yield), which represents a near upper limit to the mechanical work of a FCI. This paper presents a recalculation of the Hicks-Menzies yields for UO{sub 2} and sodium for a range of initial fuel temperatures and fuel to coolant mass ratios, using recently published UO{sub 2} and sodium equation of state data. The work presented here takes a small number of postulated FCIs with as wide range as possible of thermal interaction parameters and determines their pressure-volume P(V) and pressure-time P(t) relations, using geometrical constraints representative of the reactor. Then by examining these P(V) and P(t) curves a representative pressure-relative volume curve or range of possible curves, for use in containment analysis, is recommended

A Randomized Trial of Low-Flow Oxygen versus Nasal Continuous Positive Airway Pressure in Preterm Infants

DEFF Research Database (Denmark)

Heiring, Christian; Steensberg, Jesper; Bjerager, Mia

2015-01-01

BACKGROUND: Nasal continuous positive airway pressure (nCPAP) stabilizes the residual volume and may decrease the risk of 'atelectotrauma', potentially promoting lung development in neonates. OBJECTIVES: To assess whether replacing nCPAP by low-flow O2 by nasal cannula affects lung function...... the a/A pO2 ratio or weight gain negatively. Thus, prolonged nCPAP seems not to have a positive effect on lung function at 28 days of life and replacement by low-flow O2 could reduce the cost of equipment and increase the ease of nursing....

The volume of the carotid bodies and blood pressure variability and pulse pressure in patients with essential hypertension

International Nuclear Information System (INIS)

Jaźwiec, P.; Gać, P.; Poręba, M.; Sobieszczańska, M.; Mazur, G.; Poręba, R.

2016-01-01

Aim: To assess the relationship between the volume of the carotid bodies (V rCB+lCB ) examined by means of computed tomography angiography (CTA) and blood pressure variability and pulse pressure (PP) in 24-hour ambulatory blood pressure monitoring (ABPM) in patients with essential hypertension. Materials and methods: A group of 52 patients with essential hypertension was examined (mean age: 68.32±12.31 years), the sizes of carotid bodies were measured by means of carotid artery CTA, and 24-hour ABPM was carried out. The 24-hour ABPM established systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), PP, SBP variability (SBPV), and DBP variability (DBPV). Results: SBP, MAP, and SBPV were significantly higher in the group of hypertension patients with V rCB+lCB equal to or above the median than in the group of hypertension patients with V rCB+lCB less than the median, as well as in the group of hypertension patients with oversized carotid bodies, than in the group of hypertension patients with normal V rCB+lCB . Moreover, the PP was statistically significantly higher in the group of hypertension patients with V rCB+lCB equal to or above the median than in the group of hypertension patients with V rCB+lCB less than the median. The existence of statistically significant positive linear relationships was revealed between V rCB+lCB and SBP, PP, and SBPV. A higher body mass index, older age, smoking, and higher V rCB+lCB are independent risk factors increasing SBPV in the research group. Conclusion: A positive relationship between the size of the carotid bodies and variability of the SBP and PP is observed in patients with essential hypertension. - Highlights: • Purpose. Determination of the relationships: V rCB+lCB vs. BPV and V rCB+lCB vs. PP. • Positive linear correlations were documented between V rCB+lCB and SBP, PP and SBPV. • Higher BMI, age, V rCB+lCB and smoking are independent risk factor of increased SBPV.

Water-vapor pressure control in a volume

Science.gov (United States)

Scialdone, J. J.

1978-01-01

The variation with time of the partial pressure of water in a volume that has openings to the outside environment and includes vapor sources was evaluated as a function of the purging flow and its vapor content. Experimental tests to estimate the diffusion of ambient humidity through openings and to validate calculated results were included. The purging flows required to produce and maintain a certain humidity in shipping containers, storage rooms, and clean rooms can be estimated with the relationship developed here. These purging flows are necessary to prevent the contamination, degradation, and other effects of water vapor on the systems inside these volumes.

Lung volumes and maximal respiratory pressures in collegiate swimmers and runners.

Science.gov (United States)

Cordain, L; Tucker, A; Moon, D; Stager, J M

1990-03-01

To determine whether respiratory muscle strength is related to pulmonary volume differences in athletes and nonathletes, 11 intercollegiate female swimmers, 11 female cross-country runners, and two nonathletic control groups, matched to the athletes in height and age, were evaluated for pulmonary parameters including maximal inspiratory pressure (PImax) and maximal expiratory pressure (PEmax). Swimmers exhibited larger (p less than .05) vital capacities (VC), residual lung volumes (RV), inspiratory capacities (IC), and functional residual capacities (FRC) than both the runners or the controls but no difference (p greater than .05) in either PImax or inspiratory flow (FIV 25%-75%). Timed expiratory volumes (FEV 0.5 and FEV 1.0) were significantly (p less than .05) lower in the swimmers than in the controls. These data suggest that an adaptational growth may be responsible, in part, for the augmented static lung volumes demonstrated in swimmers.

Hyperinflation and intrinsic positive end-expiratory pressure: less room to breathe.

Science.gov (United States)

Krieger, Bruce P

2009-01-01

Clinically, the symptoms and limited exercise capabilities of patients with chronic obstructive pulmonary disease (COPD) correlate better with changes in lung volumes than with airflow measurements. The realization of the clinical importance of hyperinflation has been overshadowed for decades by the use of forced expiratory volume during 1 s (FEV(1)) and the ratio of the FEV(1) to the forced expiratory vital capacity (FEV(1)/FVC) to categorize the severity and progression of COPD. Hyperinflation is defined as an elevation in the end-expiratory lung volume or functional residual capacity. When severe hyperinflation encroaches upon inspiratory capacity and limits vital capacity, it results in elevated intrinsic positive end-expiratory pressure (PEEPi) that places the diaphragm at a mechanical disadvantage and increases the work of breathing. Severe hyperinflation is the major physiologic cause of the resulting hypercarbic respiratory failure and patients' inability to transition (i.e. wean) from mechanical ventilatory support to spontaneous breathing. This paper reviews the basic physiologic principles of hyperinflation and its clinical manifestations as demonstrated by PEEPi. Also reviewed are the adverse effects of hyperinflation and PEEPi in critically ill patients with COPD, and methods for minimizing or counterbalancing these effects. Copyright 2009 S. Karger AG, Basel.

Effective orbital volume and eyeball position: an MRI study.

Science.gov (United States)

Detorakis, Efstathios T; Drakonaki, Eleni; Papadaki, Efrosini; Pallikaris, Ioannis G; Tsilimbaris, Miltiadis K

2010-10-01

Previous studies have examined factors affecting the position of the eyeball to the orbit. This study examined the role of effective orbital volume (EOV), defined as the difference between orbital and eyeball volume, as a determinant of eyeball position, using MRI scans. Forty-six patients were recruited from the Department of Ophthalmology of the University Hospital of Heraklion, Crete Greece. Patients with a history of orbital disease were excluded. Distances between eyeball poles and orbital landmarks were measured in T1 weighted transverse, sagittal and coronal orbital images. The protrusion of the eyeball in the sagittal and transverse planes was recorded. The volume of the eyeball and bony orbit, the EOV, the volume of the extraocular muscles as well as clinical information (age, gender, Hertel exophthalmometry) were also recorded. EOV was significantly associated with orbital volume but not with eyeball volume. EOV was also significantly associated with transverse and sagittal globe protrusions. Females displayed significantly lower orbital and eyeball volumes as well as EOV than males but higher transverse globe protrusion than males. Variations in EOV are associated with orbital volume rather than with eyeball volume. EOV is associated with globe protrusion and may be taken into account in the planning of various procedures, including orbital decompression, treatment of enophthalmos or the size of orbital implants following enucleation.

Molar volume dependence of the pressure of solid 3He at very low temperatures

International Nuclear Information System (INIS)

Mamiya, T.; Sawada, A.; Fukuyama, H.; Iwahashi, K.; Masuda, Y.

1983-01-01

The pressure of solid 3 He has been measured as a function of temperature T between 0.3 and 50 mK at molar volumes between 24.19 and 23.31 cm 3 . The entropy discontinuity obtained from the pressure jump at the ordering transition turned out to be almost independent of molar volumes, being about 0.40Rln2 in the studied range of molar volumes

Peripheral arterial volume distensibility: significant differences with age and blood pressure measured using an applied external pressure

International Nuclear Information System (INIS)

Zheng, Dingchang; Murray, Alan

2011-01-01

A new arterial distensibility measurement technique was assessed in 100 healthy normotensive subjects. Arterial transmural pressures on the whole right arm were reduced with a 50 cm long cuff inflated to 10, 20, 30 and 40 mmHg. The electrocardiogram, and finger and ear photoplethysmograms were recorded simultaneously. Arm pulse propagation time, pulse wave velocity (PWV) and arterial volume distensibility were determined. With a 40 mmHg reduction in transmural pressure, arm pulse propagation time increased from 61 to 83 ms, PWV decreased from 12 to 8 m s −1 and arterial distensibility increased from 0.102% to 0.232% per mmHg (all P < 0.0001). At all cuff pressures, arterial distensibility was significantly related to resting mean arterial pressure (MAP), diastolic blood pressure (DBP) and age, and for systolic blood pressure at 30 and 40 mmHg (all P < 0.05). At 40 mmHg cuff pressure, arterial distensibility fell by 54% for a MAP increase from 75 to 105 mmHg, 57% for a DBP increase from 60 to 90 mmHg and 47% for an age increase from 20 to 70 years. These changes were more than double than those without cuff pressure. Our technique showed that systemic volume distensibility of the peripheral arm artery reduced with age, with a greater effect at higher external and lower transmural pressures

Continuous positive airway pressure therapy: new generations.

LENUS (Irish Health Repository)

Garvey, John F

2010-02-01

Continuous positive airway pressure (CPAP) is the treatment of choice for obstructive sleep apnoea syndrome (OSAS). However, CPAP is not tolerated by all patients with OSAS and alternative modes of pressure delivery have been developed to overcome pressure intolerance, thereby improving patient comfort and adherence. Auto-adjustable positive airway pressure (APAP) devices may be utilised for the long-term management of OSAS and may also assist in the initial diagnosis of OSAS and titration of conventional CPAP therapy. Newer modalities such as C-Flex and A-Flex also show promise as treatment options in the future. However, the evidence supporting the use of these alternative modalities remains scant, in particular with regard to long-term cardiovascular outcomes. In addition, not all APAP devices use the same technological algorithms and data supporting individual APAP devices cannot be extrapolated to support all. Further studies are required to validate the roles of APAP, C-Flex and A-Flex. In the interim, standard CPAP therapy should continue as the mainstay of OSAS management.

Continuous positive airway pressure therapy: new generations.

LENUS (Irish Health Repository)

Garvey, John F

2012-02-01

Continuous positive airway pressure (CPAP) is the treatment of choice for obstructive sleep apnoea syndrome (OSAS). However, CPAP is not tolerated by all patients with OSAS and alternative modes of pressure delivery have been developed to overcome pressure intolerance, thereby improving patient comfort and adherence. Auto-adjustable positive airway pressure (APAP) devices may be utilised for the long-term management of OSAS and may also assist in the initial diagnosis of OSAS and titration of conventional CPAP therapy. Newer modalities such as C-Flex and A-Flex also show promise as treatment options in the future. However, the evidence supporting the use of these alternative modalities remains scant, in particular with regard to long-term cardiovascular outcomes. In addition, not all APAP devices use the same technological algorithms and data supporting individual APAP devices cannot be extrapolated to support all. Further studies are required to validate the roles of APAP, C-Flex and A-Flex. In the interim, standard CPAP therapy should continue as the mainstay of OSAS management.

Analysis of the static pressure volume curve of the lung in experimentally induced pulmonary damage by CT-densitometry

International Nuclear Information System (INIS)

David, M.; Karmrodt, J.; Herwelling, A.; Bletz, C.; David, S.; Heussel, C.P.; Markstaller, K.

2005-01-01

Purpose: To study quantitative changes of lung density distributions when recording in- and expiratory static pressure-volume curves by single slice computed tomography (CT). Materials and Methods: Static in- and expiratory pressure volume curves (0 to 1000 ml, increments of 100 ml) were obtained in random order in 10 pigs after induction of lung damage by saline lavage. Simultaneously, CT acquisitions (slice thickness 1 mm, temporal increment 2 s) were performed in a single slice (3 cm below the carina). In each CT image lung segmentation and planimetry of defined density ranges were achieved. The lung density ranges were defined as: hyperinflated (-1024 to -910 HU), normal aerated (-910 to -600 HU), poorly aerated (-600 to -300 HU), and non aerated (-300 to 200 HU) lung. Fractional areas of defined density ranges in percentage of total lung area were compared to recorded volume increments and airway pressures (atmospheric pressure, lower inflection point (LIP), LIP*0.5, LIP*1.5, peak airway pressure) of in- and expiratory pressure-volume curves. Results: Quantitative analysis of defined density ranges showed no differences between in- and expiratory pressure-volume curves. The amount of poorly aerated lung decreased and normal aerated lung increased constantly when airway pressure and volume were increased during inspiratory pressure-volume curves and vice versa during expiratory pressure-volume loops. Conclusion: Recruitment and derecruitment of lung atelectasis during registration of static in- and expiratory pressure-volume loops occurred constantly, but not in a stepwise manner. CT was shown to be an appropriate method to analyse these recruitment process. (orig.)

Volumes of virtual modifications and virtual polymorphous transformations in transition metals under pressure

International Nuclear Information System (INIS)

Zil'bershtejn, V.A.; Zaretskij, L.B.; Ehstrin, Eh.I.

1975-01-01

To find out what phases are likely to occur under pressure, it is necessary to know the relative density of various modifications, that is the ratio of the volumes of stable and virtual modifications and generally speaking the ratio of the phase compressibility. If the virtual phase volume is less than the volume of the stable phase, then such a phase is likely to appear under pressure. A method has been developed for computing the volumes of the virtual modifications from the data on the solid solutions lattice parameters. Testing the applicability of the method for a number of systems with a complete mutual solubility has shown, that the method proposed permits to estimate the volumes of the transition metals virtual modifications with the error probably not exceeding 1%. The analysis was made of the data available on the solid solutions of transition metals with fcc-, bcc- and hcp-lattices. The virtual volumes have been computed for hcp-iridium, hcp-rhodium, hcp-molybdenum, fcc-molybdenum, fcc-chromium, bcc-rhenium, bcc-ruthenium and bcc-technetium. The data obtained on the virtual modifications volumes permit to assume that the pressure increase is likely to result in the phase transformations of fcc-hcp in iridium and rhodium, and bcc-hcp in molybdenum, while evidently the transformations of bcc-fcc in molybdenum and chromium, hcp-bcc in technetium, rhenium and ruthenium are impossible. The pressure resulting in the transformations in the metals investigated equals approximately hundreds of kbar, or even approximately 1 Mbar for Ir

Noninvasive Positive Pressure Ventilatory Support Begins During Sleep.

Science.gov (United States)

Bach, John R

2017-12-01

The goal of sleep doctors has been to titrate away apneas and hypopneas using noninvasive ventilation, a term that has become synonymous with continuous positive airway pressure and bilevel positive airway pressure at the lowest effective bilevel settings. It is now time to appreciate noninvasive ventilatory support as an alternative to invasive mechanical ventilation. This article discusses mechanisms of action, two paradigms, and ancillary techniques for noninvasive ventilatory support. Copyright © 2017 Elsevier Inc. All rights reserved.

A comparison of volume control and pressure-regulated volume control ventilation in acute respiratory failure

OpenAIRE

Guldager, Henrik; Nielsen, Soeren L; Carl, Peder; Soerensen, Mogens B

1997-01-01

Background: The aim of this study was to test the hypothesis that a new mode of ventilation (pressure-regulated volume control; PRVC) is associated with improvements in respiratory mechanics and outcome when compared with conventional volume control (VC) ventilation in patients with acute respiratory failure. We conducted a randomised, prospective, open, cross over trial on 44 patients with acute respiratory failure in the general intensive care unit of a university hospital. After a stabiliz...

A comparison of volume control and pressure-regulated volume control ventilation in acute respiratory failure

Science.gov (United States)

Guldager, Henrik; Nielsen, Soeren L; Carl, Peder; Soerensen, Mogens B

1997-01-01

Background: The aim of this study was to test the hypothesis that a new mode of ventilation (pressure-regulated volume control; PRVC) is associated with improvements in respiratory mechanics and outcome when compared with conventional volume control (VC) ventilation in patients with acute respiratory failure. We conducted a randomised, prospective, open, cross over trial on 44 patients with acute respiratory failure in the general intensive care unit of a university hospital. After a stabilization period of 8 h, a cross over trial of 2 × 2 h was conducted. Apart from the PRVC/VC mode, ventilator settings were comparable. The following parameters were recorded for each patient: days on ventilator, failure in the assigned mode of ventilation (peak inspiratory pressure > 50 cmH2O) and survival. Results: In the crossover trial, peak inspiratory pressure was significantly lower using PRVC than with VC (20 cmH2O vs 24 cmH2O, P < 0.0001). No other statistically significant differences were found. Conclusions: Peak inspiratory pressure was significantly lower during PRVC ventilation than during VC ventilation, and thus PRVC may be superior to VC in certain patients. However, in this small group of patients, we could not demonstrate that PRVC improved outcome. PMID:11056699

Noninvasive Positive Pressure Ventilation or Conventional Mechanical Ventilation for Neonatal Continuous Positive Airway Pressure Failure

Directory of Open Access Journals (Sweden)

Zohreh Badiee

2014-01-01

Full Text Available Background: The aim of this study was to assess the success rate of nasal intermittent positive pressure ventilation (NIPPV for treatment of continuous positive airway pressure (CPAP failure and prevention of conventional ventilation (CV in preterm neonates. Methods: Since November 2012 to April 2013, a total number of 55 consecutive newborns with gestational ages of 26-35 weeks who had CPAP failure were randomly assigned to one of the two groups. The NIPPV group received NIPPV with the initial peak inspiratory pressure (PIP of 16-20 cmH 2 O and frequency of 40-60 breaths/min. The CV group received PIP of 12-20 cmH 2 O and frequency of 40-60 breaths/min. Results: About 74% of newborns who received NIPPV for management of CPAP failure responded to NIPPV and did not need intubation and mechanical ventilation. Newborns with lower postnatal age at entry to the study and lower 5 min Apgar score more likely had NIPPV failure. In addition, treatment failure was higher in newborns who needed more frequent doses of surfactant. Duration of oxygen therapy was 9.28 days in CV group and 7.77 days in NIPPV group (P = 0.050. Length of hospital stay in CV group and NIPPV groups were 48.7 and 41.7 days, respectively (P = 0.097. Conclusions: NIPPV could decrease the need for intubation and mechanical ventilation in preterm infants with CPAP failure.

Respiratory effects of low versus high tidal volume with or without positive end-expiratory pressure in anesthetized dogs with healthy lungs.

Science.gov (United States)

De Monte, Valentina; Bufalari, Antonello; Grasso, Salvatore; Ferrulli, Fabienne; Crovace, Alberto Maria; Lacitignola, Luca; Staffieri, Francesco

2018-05-01

OBJECTIVE To evaluate the impact of 2 tidal volumes (T V s) with or without positive end-expiratory pressure (PEEP) on lung mechanics, aeration, and gas exchange in healthy anesthetized dogs. ANIMALS 40 mixed-breed dogs with healthy lungs. PROCEDURES Anesthetized dogs were randomly assigned to 4 groups (n = 10/group) with different ventilatory settings: T V of 8 mL/kg and PEEP of 0 cm H 2 O (low T V group), T V of 8 mL/kg and PEEP of 5 cm H 2 O (low T V plus PEEP group), T V of 15 mL/kg and PEEP of 0 cm H 2 O (high T V group), or T V of 15 mL/kg and PEEP of 5 cm H 2 O (high T V plus PEEP group). Expired CO 2 and respiratory rate were titrated on the basis of a predetermined stepwise protocol. Gas exchange, respiratory mechanics, and pulmonary aeration were evaluated by means of CT 30 minutes after starting mechanical ventilation at the assigned setting. RESULTS Partial pressures of arterial and expired CO 2 were higher in the low T V and low T V plus PEEP groups than in the high T V and high T V plus PEEP groups. Peak and plateau airway pressures were higher in the PEEP group than in the other groups. Static lung compliance was higher in the high T V plus PEEP group than in the low T V group. Relative percentages of atelectatic and poorly aerated lung were lower in the high T V plus PEEP group than in the other groups. Oxygenation was similar among groups. CONCLUSIONS AND CLINICAL RELEVANCE Differences in T V and PEEP application during mechanical ventilation may affect respiratory function in anesthetized dogs with healthy lungs. Ventilation with a T V of 15 mL/kg and PEEP of 5 cm H 2 O significantly improved lung compliance and reduced the amount of atelectatic and poorly aerated lung.

Physiologic Evaluation of Ventilation Perfusion Mismatch and Respiratory Mechanics at Different Positive End-expiratory Pressure in Patients Undergoing Protective One-lung Ventilation.

Science.gov (United States)

Spadaro, Savino; Grasso, Salvatore; Karbing, Dan Stieper; Fogagnolo, Alberto; Contoli, Marco; Bollini, Giacomo; Ragazzi, Riccardo; Cinnella, Gilda; Verri, Marco; Cavallesco, Narciso Giorgio; Rees, Stephen Edward; Volta, Carlo Alberto

2018-03-01

Arterial oxygenation is often impaired during one-lung ventilation, due to both pulmonary shunt and atelectasis. The use of low tidal volume (VT) (5 ml/kg predicted body weight) in the context of a lung-protective approach exacerbates atelectasis. This study sought to determine the combined physiologic effects of positive end-expiratory pressure and low VT during one-lung ventilation. Data from 41 patients studied during general anesthesia for thoracic surgery were collected and analyzed. Shunt fraction, high V/Q and respiratory mechanics were measured at positive end-expiratory pressure 0 cm H2O during bilateral lung ventilation and one-lung ventilation and, subsequently, during one-lung ventilation at 5 or 10 cm H2O of positive end-expiratory pressure. Shunt fraction and high V/Q were measured using variation of inspired oxygen fraction and measurement of respiratory gas concentration and arterial blood gas. The level of positive end-expiratory pressure was applied in random order and maintained for 15 min before measurements. During one-lung ventilation, increasing positive end-expiratory pressure from 0 cm H2O to 5 cm H2O and 10 cm H2O resulted in a shunt fraction decrease of 5% (0 to 11) and 11% (5 to 16), respectively (P ventilation, high positive end-expiratory pressure levels improve pulmonary function without increasing high V/Q and reduce driving pressure.

Computing the partial volume of pressure vessels

Energy Technology Data Exchange (ETDEWEB)

Wiencke, Bent [Nestle USA, Corporate Engineering, 800 N. Brand Blvd, Glendale, CA 91203 (United States)

2010-06-15

The computation of the partial and total volume of pressure vessels with various type of head profiles requires detailed knowledge of the head profile geometry. Depending on the type of head profile the derivation of the equations can become very complex and the calculation process cumbersome. Certain head profiles require numerical methods to obtain the partial volume, which for most application is beyond the scope of practicability. This paper suggests a unique method that simplifies the calculation procedure for the various types of head profiles by using one common set of equations without the need for numerical or complex computation methods. For ease of use, all equations presented in this paper are summarized in a single table format for horizontal and vertical vessels. (author)

Effect of increases in lung volume on clearance of aerosolized solute from human lungs

Energy Technology Data Exchange (ETDEWEB)

Marks, J.D.; Luce, J.M.; Lazar, N.M.; Wu, J.N.; Lipavsky, A.; Murray, J.F.

1985-10-01

To study the effect of increases in lung volume on solute uptake, we measured clearance of /sup 99m/Tc-diethylenetriaminepentaacetic acid (Tc-DTPA) at different lung volumes in 19 healthy humans. Seven subjects inhaled aerosols (1 micron activity median aerodynamic diam) at ambient pressure; clearance and functional residual capacity (FRC) were measured at ambient pressure (control) and at increased lung volume produced by positive pressure (12 cmH2O continuous positive airway pressure (CPAP)) or negative pressure (voluntary breathing). Six different subjects inhaled aerosol at ambient pressure; clearance and FRC were measured at ambient pressure and CPAP of 6, 12, and 18 cmH2O pressure. Six additional subjects inhaled aerosol at ambient pressure or at CPAP of 12 cmH2O; clearance and FRC were determined at CPAP of 12 cmH2O. According to the results, Tc-DTPA clearance from human lungs is accelerated exponentially by increases in lung volume, this effect occurs whether lung volume is increased by positive or negative pressure breathing, and the effect is the same whether lung volume is increased during or after aerosol administration. The effect of lung volume must be recognized when interpreting the results of this method.

Effect of increases in lung volume on clearance of aerosolized solute from human lungs

International Nuclear Information System (INIS)

Marks, J.D.; Luce, J.M.; Lazar, N.M.; Wu, J.N.; Lipavsky, A.; Murray, J.F.

1985-01-01

To study the effect of increases in lung volume on solute uptake, we measured clearance of /sup 99m/Tc-diethylenetriaminepentaacetic acid (Tc-DTPA) at different lung volumes in 19 healthy humans. Seven subjects inhaled aerosols (1 micron activity median aerodynamic diam) at ambient pressure; clearance and functional residual capacity (FRC) were measured at ambient pressure (control) and at increased lung volume produced by positive pressure [12 cmH 2 O continuous positive airway pressure (CPAP)] or negative pressure (voluntary breathing). Six different subjects inhaled aerosol at ambient pressure; clearance and FRC were measured at ambient pressure and CPAP of 6, 12, and 18 cmH 2 O pressure. Six additional subjects inhaled aerosol at ambient pressure or at CPAP of 12 cmH 2 O; clearance and FRC were determined at CPAP of 12 cmH 2 O. According to the results, Tc-DTPA clearance from human lungs is accelerated exponentially by increases in lung volume, this effect occurs whether lung volume is increased by positive or negative pressure breathing, and the effect is the same whether lung volume is increased during or after aerosol administration. The effect of lung volume must be recognized when interpreting the results of this method

Improvised bubble continuous positive airway pressure (BCPAP ...

African Journals Online (AJOL)

Improvised bubble continuous positive airway pressure (BCPAP) device at the National Hospital Abuja gives immediate improvement in respiratory rate and oxygenation in neonates with respiratory distress.

Estimation of lung volume and pulmonary blood volume from radioisotopic images

International Nuclear Information System (INIS)

Kanazawa, Minoru

1989-01-01

Lung volume and pulmonary blood volume in man were estimated from the radioisotopic image using single photon emission computed tomography (SPECT). Six healthy volunteers were studied in a supine position with normal and altered lung volumes by applying continuous negative body-surface pressure (CNP) and by positive end-expiratory pressure (PEEP). 99m Tc labeled human serum albumin was administered as an aerosol to image the lungs. The CNP caused the diaphragm to be lowered and it increased the mean lung tissue volume obtained by SPECT from 3.09±0.49 l for baseline to 3.67±0.62 l for 10 cmH 2 O (p 2 O (p 2 O), respectively. The PEEP also increased the lung tissue volume to 3.68±0.68 l for 10 cmH 2 O as compared with the baseline (p 2 O PEEP. The lung tissue volume obtained by SPECT showed a positive correlation with functional residual capacity measured by the He dilution method (r=0.91, p 99m Tc-labeled red blood cells. The L/H ratio decreased after either the CNP or PEEP, suggesting a decrease in the blood volume per unit lung volume. However, it was suggested that the total pulmonary blood volume increased slightly either on the CNP (+7.4% for 10 cmH 2 O, p 2 O,p<0.05) when we extrapolated the L/H ratio to the whole lungs by multiplying the lung tissue volume obtained by SPECT. We concluded that SPECT could offer access to the estimation of lung volume and pulmonary blood volume in vivo. (author)

Running on a lower-body positive pressure treadmill

DEFF Research Database (Denmark)

Raffalt, Peter C; Hovgaard-Hansen, Line; Jensen, Bente Rona

2013-01-01

This study investigated maximal oxygen consumption (VO2max) and time to exhaustion while running on a lower-body positive pressure treadmill (LBPPT) at normal body weight (BW) as well as how BW support affects respiratory responses, ground reaction forces, and stride characteristics.......This study investigated maximal oxygen consumption (VO2max) and time to exhaustion while running on a lower-body positive pressure treadmill (LBPPT) at normal body weight (BW) as well as how BW support affects respiratory responses, ground reaction forces, and stride characteristics....

Moderately high frequency ventilation with a conventional ventilator allows reduction of tidal volume without increasing mean airway pressure.

Science.gov (United States)

Cordioli, Ricardo Luiz; Park, Marcelo; Costa, Eduardo Leite Vieira; Gomes, Susimeire; Brochard, Laurent; Amato, Marcelo Britto Passos; Azevedo, Luciano Cesar Pontes

2014-12-01

The aim of this study was to explore if positive-pressure ventilation delivered by a conventional ICU ventilator at a moderately high frequency (HFPPV) allows a safe reduction of tidal volume (V T) below 6 mL/kg in a porcine model of severe acute respiratory distress syndrome (ARDS) and at a lower mean airway pressure than high-frequency oscillatory ventilation (HFOV). This is a prospective study. In eight pigs (median weight 34 [29,36] kg), ARDS was induced by pulmonary lavage and injurious ventilation. The animals were ventilated with a randomized sequence of respiratory rates: 30, 60, 90, 120, 150, followed by HFOV at 5 Hz. At each step, V T was adjusted to allow partial pressure of arterial carbon dioxide (PaCO2) to stabilize between 57 and 63 mmHg. Data are shown as median [P25th,P75th]. After lung injury, the PaO2/FiO2 (P/F) ratio was 92 [63,118] mmHg, pulmonary shunt 26 [17,31]%, and static compliance 11 [8,14] mL/cmH2O. Positive end-expiratory pressure (PEEP) was 14 [10,17] cmH2O. At 30 breaths/min, V T was higher than 6 (7.5 [6.8,10.2]) mL/kg, but at all higher frequencies, V T could be reduced and PaCO2 maintained, leading to reductions in plateau pressures and driving pressures. For frequencies of 60 to 150/min, V T progressively fell from 5.2 [5.1,5.9] to 3.8 [3.7,4.2] mL/kg (p mechanics, auto-PEEP generation, hemodynamics, or gas exchange. Mean airway pressure was maintained constant and was increased only during HFOV. During protective mechanical ventilation, HFPPV delivered by a conventional ventilator in a severe ARDS swine model safely allows further tidal volume reductions. This strategy also allowed decreasing airway pressures while maintaining stable PaCO2 levels.

Proportional positive airway pressure: a new concept to treat obstructive sleep apnoea.

Science.gov (United States)

Juhász, J; Becker, H; Cassel, W; Rostig, S; Peter, J H

2001-03-01

Proportional positive airway pressure (PPAP) was designed to optimize airway pressure for the therapy of obstructive sleep apnoea (OSA). In a randomized crossover prospective study, the clinical feasibility of PPAP and its immediate effects on the breathing disorder and sleep in comparison with continuous positive airway pressure (CPAP) was evaluated. Twelve patients requiring CPAP therapy underwent CPAP and PPAP titration in a random order. Obstructive and mixed respiratory events could be completely abolished with both forms of treatment. This efficacy could be achieved at a significantly lower mean mask pressure during PPAP titration (8.45+/-2.42 cmH2O) compared to CPAP (9.96+/-2.7 cmH2O) (p=0.002). The mean minimal arterial oxygen saturation (Sa,O2) (82.8+/-6.5%) on the diagnostic night increased significantly (pPPAP titration. Total sleep time, slow wave sleep and rapid eye movement (REM) sleep increased significantly by the same amount during both CPAP and PPAP titration (pPPAP titration night, four patients did not have a preference, and two patients preferred CPAP. The present data show that proportional positive airway pressure is as effective as continuous positive airway pressure in eliminating obstructive events and has the same immediate effect on sleep. The lower average mask pressure during proportional positive airway pressure implies potential advantages compared to continuous positive airway pressure. Proportional positive airway pressure presents a new effective therapeutic approach to obstructive sleep apnoea.

The effect of intraocular gas and fluid volumes on intraocular pressure.

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Simone, J N; Whitacre, M M

1990-02-01

Large increases in the intraocular pressure (IOP) of postoperative gas-containing eyes may require the removal of gas or fluid to reduce the IOP to the normal range. Application of the ideal gas law to Friedenwald's equation provides a mathematical model of the relationship between IOP, intraocular gas and fluid volumes, and the coefficient of scleral rigidity. This mathematic model shows that removal of a given volume of gas or fluid produces an identical decrease in IOP and that the more gas an eye contains, the greater the volume reduction necessary to reduce the pressure. Application of the model shows that the effective coefficient of scleral rigidity is low (mean K, 0.0021) in eyes with elevated IOP that have undergone vitrectomy and retinal cryopexy and very low (mean K, 0.0013) in eyes with elevated IOP that have undergone placement of a scleral buckle and band. By using the appropriate mean coefficient of rigidity, the volume of material to be aspirated to produce a given decrease in IOP can be predicted with clinically useful accuracy.

Comparison of intermittent positive pressure breathing and temporary positive expiratory pressure in patients with severe chronic obstructive pulmonary disease.

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Nicolini, Antonello; Mollar, Elena; Grecchi, Bruna; Landucci, Norma

2014-01-01

Results supporting the use and the effectiveness of positive expiratory, pressure devices in chronic obstructive pulmonary disease (COPD) patients are still controversial, We have tested the hypothesis that adding TPEP or IPPB to standard pharmacological therapy may provide additional clinical benefit over, pharmacological therapy only in patients with severe COPD. Fourty-five patients were randomized in three groups: a group was treated; with IPPB,a group was treated with TPEP and a group with pharmacological; therapy alone (control group). Primary outcome measures included the measurement of scale or, questionnaire concerning dyspnea (MRC scale),dyspnea,cough, and, sputum (BCSS) and quality of life (COPD assessment test) (CAT). Secondary, outcome measures were respiratory function testing,arterial blood gas,analysis,and hematological examinations. Both patients in the IPPB group and in the TPEP group showed a significant, improvement in two of three tests (MRC,CAT) compared to the control, group.However,in the group comparison analysis for, the same variables between IPPB group and TPEP group we observed a, significant improvement in the IPPB group (P≤.05 for MRC and P≤.01 for, CAT). The difference of action of the two techniques are evident in the results of, pulmonary function testing: IPPB increases FVC, FEV1, and MIP; this reflects, its capacity to increase lung volume. Also TPEP increases FVC and FEV1 (less, than IPPB), but increases MEP, while decreasing total lung capacity and, residual volume. The two techniques (IPPB and TPEP) improves significantly dyspnea; quality of; life tools and lung function in patients with severe COPD. IPPB demonstrated a greater effectiveness to improve dyspnea and quality of life tools (MRC, CAT) than TPEP. Copyright © 2013 SEPAR. Published by Elsevier Espana. All rights reserved.

Effects of body position and sex group on tongue pressure generation.

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Dietsch, Angela M; Cirstea, Carmen M; Auer, Ed T; Searl, Jeff P

2013-11-01

Fine control of orofacial musculature is necessary to precisely accelerate and decelerate the articulators across exact distances for functional speech and coordinated swallows (Amerman & Parnell, 1990; Benjamin, 1997; Kent, Duffy, Slama, Kent, & Clift, 2001). Enhanced understanding of neural control for such movements could clarify the nature of and potential remediation for some dysarthrias and other orofacial myofunctional impairments. Numerous studies have measured orolingual force and accuracy during speech and nonspeech tasks, but have focused on young adults, maximum linguapalatal pressures, and upright positioning (O'Day, Frank, Montgomery, Nichols, & McDade, 2005; Solomon & Munson, 2004; Somodi, Robin, & Luschei, 1995; Youmans, Youmans, & Stierwalt, 2009). Patients' medical conditions or testing procedures such as concurrent neuroimaging may preclude fully upright positioning during oral motor assessments in some cases. Since judgments about lingual strength and coordination can influence clinical decisions regarding the functionality of swallowing and speech, it is imperative to understand any effects of body positioning differences. In addition, sex differences in the control of such tasks are not well defined. Therefore, this study evaluated whether pressures exerted during tongue movements differ in upright vs. supine body position in healthy middle-aged men and women. Twenty healthy middle-aged adults compressed small air-filled plastic bulbs in the oral cavity at predetermined fractions of task-specific peak pressure in a randomized block design. Tasks including phoneme repetitions and nonspeech isometric contractions were executed in upright and supine positions. Participants received continuous visual feedback regarding targets and actual exerted pressures. Analyses compared average pressure values for each subject, task, position, and effort level. Speech-like and nonspeech tongue pressures did not differ significantly across body position or sex

Utilization of the lower inflection point of the pressure-volume curve results in protective conventional ventilation comparable to high frequency oscillatory ventilation in an animal model of acute respiratory distress syndrome

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Felipe S. Rossi

2008-01-01

Full Text Available INTRODUCTION: Studies comparing high frequency oscillatory and conventional ventilation in acute respiratory distress syndrome have used low values of positive end-expiratory pressure and identified a need for better recruitment and pulmonary stability with high frequency. OBJECTIVE: To compare conventional and high frequency ventilation using the lower inflection point of the pressure-volume curve as the determinant of positive end-expiratory pressure to obtain similar levels of recruitment and alveolar stability. METHODS: After lung lavage of adult rabbits and lower inflection point determination, two groups were randomized: conventional (positive end-expiratory pressure = lower inflection point; tidal volume=6 ml/kg and high frequency ventilation (mean airway pressures= lower inflection point +4 cmH2O. Blood gas and hemodynamic data were recorded over 4 h. After sacrifice, protein analysis from lung lavage and histologic evaluation were performed. RESULTS: The oxygenation parameters, protein and histological data were similar, except for the fact that significantly more normal alveoli were observed upon protective ventilation. High frequency ventilation led to lower PaCO2 levels. DISCUSSION: Determination of the lower inflection point of the pressure-volume curve is important for setting the minimum end expiratory pressure needed to keep the airways opened. This is useful when comparing different strategies to treat severe respiratory insufficiency, optimizing conventional ventilation, improving oxygenation and reducing lung injury. CONCLUSIONS: Utilization of the lower inflection point of the pressure-volume curve in the ventilation strategies considered in this study resulted in comparable efficacy with regards to oxygenation and hemodynamics, a high PaCO2 level and a lower pH. In addition, a greater number of normal alveoli were found after protective conventional ventilation in an animal model of acute respiratory distress syndrome.

[Possibilities of bi-level positive pressure ventilation in chronic hypoventilation].

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Saaresranta, Tarja; Anttalainen, Ulla; Polo, Olli

2011-01-01

During the last decade, noninvasive bi-level positive pressure ventilation has enabled respiratory support in inpatient wards and at home. In many cases, a bi-level airway pressure ventilator can be used to avoid artificial airway and respirator therapy, and may shorten hospital stay and save costs. The treatment alleviates the patient's dyspnea and fatigue, whereby the quality of life improves, and in certain situations also the life span increases. The implementation of bi-level positive pressure ventilation by the physician requires knowledge of the basics of respiratory physiology and familiarization with the bi-level airway pressure ventilator.

Asystole following positive pressure insufflation of right pleural cavity: a case report

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Konia Mojca R

2011-06-01

Full Text Available Abstract Introduction Adverse hemodynamic effects with severe bradycardia have been previously reported during positive pressure insufflation of the right thoracic cavity in humans. To the best of our knowledge, this is the first report of asystole during thoracoscopic surgery with positive pressure insufflation. Case presentation A 63-year-old Caucasian woman developed asystole at the onset of positive pressure insufflation of her right hemithorax during a thoracoscopic single-lung ventilation procedure. Immediate deflation of pleural cavity, intravenous glycopyrrolate and atropine administration returned her heart rhythm to normal sinus rhythm. The surgery proceeded in the absence of positive pressure insufflation without any further complications. Conclusions We discuss the proposed mechanisms of hemodynamic instability with positive pressure thoracic insufflation, and anesthetic and insufflation techniques that decrease the likelihood of adverse hemodynamic events.

Effects of Modes, Obesity, and Body Position on Non-invasive Positive Pressure Ventilation Success in the Intensive Care Unit: A Randomized Controlled Study.

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Türk, Murat; Aydoğdu, Müge; Gürsel, Gül

2018-01-01

Different outcomes and success rates of non-invasive positive pressure ventilation (NPPV) in patients with acute hypercapnic respiratory failure (AHRF) still pose a significant problem in intensive care units. Previous studies investigating different modes, body positioning, and obesity-associated hypoventilation in patients with chronic respiratory failure showed that these factors may affect ventilator mechanics to achieve a better minute ventilation. This study tried to compare pressure support (BiPAP-S) and average volume targeted pressure support (AVAPS-S) modes in patients with acute or acute-on-chronic hypercapnic respiratory failure. In addition, short-term effects of body position and obesity within both modes were analyzed. We conducted a randomized controlled study in a 7-bed intensive care unit. The course of blood gas analysis and differences in ventilation variables were compared between BiPAP-S (n=33) and AVAPS-S (n=29), and between semi-recumbent and lateral positions in both modes. No difference was found in the length of hospital stay and the course of PaCO2, pH, and HCO3 levels between the modes. There was a mean reduction of 5.7±4.1 mmHg in the PaCO2 levels in the AVAPS-S mode, and 2.7±2.3 mmHg in the BiPAP-S mode per session (ppositioning had no notable effect in both modes. Although the decrease in the PaCO2 levels in the AVAPS-S mode per session was remarkably high, the course was similar in both modes. Furthermore, obesity and body positioning had no prominent effect on the PaCO2 response and ventilator mechanics. Post hoc power analysis showed that the sample size was not adequate to detect a significant difference between the modes.

The importance of clinical monitoring for compliance with Continuous Positive Airway Pressure.

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Pelosi, Lucas B; Silveira, Mariana L C; Eckeli, Alan L; Chayamiti, Emilia M P C; Almeida, Leila A; Sander, Heidi H; Küpper, Daniel S; Valera, Fabiana C P

Obstructive sleep apnea syndrome is currently a public health problem of great importance. When misdiagnosed or improperly treated, it can lead to serious consequences on patients' quality of life. The gold standard treatment for cases of obstructive sleep apnea syndrome, especially in mild to severe and symptomatic cases, is continuous positive airway pressure therapy. Compliance with continuous positive airway pressure therapy is directly dependent on the active participation of the patient, which can be influenced by several factors. The objective of this study is to describe the factors related to compliance with continuous positive airway pressure therapy, and to analyze which associated factors directly influence the efficiency of the treatment. Patients who received continuous positive airway pressure therapy through the Municipal Health Department of the city of Ribeirão Preto were recruited. A structured questionnaire was administered to the patients. Compliance with continuous positive airway pressure therapy was assessed by average hours of continuous positive airway pressure therapy usage per night. Patients with good compliance (patients using continuous positive airway pressure therapy ≥4h/night) were compared to those with poor compliance (patients using <4h/night). 138 patients were analyzed: 77 (55.8%) were considered compliant while 61 (44.2%) were non-compliant. The comparison between the two groups showed that regular monitoring by a specialist considerably improved compliance with continuous positive airway pressure therapy (odds ratio, OR=2.62). Compliance with continuous positive airway pressure therapy is related to educational components, which can be enhanced with continuous and individualized care to patients with obstructive sleep apnea syndrome. Copyright © 2016 Associação Brasileira de Otorrinolaringologia e Cirurgia Cérvico-Facial. Published by Elsevier Editora Ltda. All rights reserved.

Positioning bedridden patients to reduce interface pressures over the sacrum and great trochanter.

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Yoshikawa, Y; Maeshige, N; Sugimoto, M; Uemura, M; Noguchi, M; Terashi, H

2015-07-01

In this study, we evaluated the effect of hip-joint rotation on the interface pressure over the sacrum and greater trochanter with a new protocol for positioning of bedridden elderly patients. The interface pressure values over the sacrum and greater trochanter in bedridden patients were evaluated. These were collected in the supine position, 90° lateral position, and 30° and 40° laterally inclined positions with external rotation or neutral positioning of the hip joint. Each interface pressure was assessed with a device measuring pressure distribution, after which, the peak pressure index (PPI) was calculated. In the 17 patients examined, the PPI over the sacrum in the supine position was significantly greater than that in other positions. In the 30° and 40° laterally inclined positions, the PPIs over the greater trochanter were significantly lower in the neutral position of the hip joint compared with those in the external rotation position. Our findings revealed the effects of hip-joint rotation on the interface pressure for the greater trochanter, possibly due to the increased distance between the greater trochanter and the sacrum caused by neutral position of the hip joint. The results demonstrate that it is to best place the hip joint in a neutral position when the legs are in contact with the bed in order to distribute the pressure over the greater trochanter in the 30° and 40° laterally inclined positions. These results can be applied to the clinical setting to improve patient positioning and decrease pressure ulcers. The authors declare that they have no competing financial interests.

The influence of body position on cerebrospinal fluid pressure gradient and movement in cats with normal and impaired craniospinal communication.

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Klarica, Marijan; Radoš, Milan; Erceg, Gorislav; Petošić, Antonio; Jurjević, Ivana; Orešković, Darko

2014-01-01

Intracranial hypertension is a severe therapeutic problem, as there is insufficient knowledge about the physiology of cerebrospinal fluid (CSF) pressure. In this paper a new CSF pressure regulation hypothesis is proposed. According to this hypothesis, the CSF pressure depends on the laws of fluid mechanics and on the anatomical characteristics inside the cranial and spinal space, and not, as is today generally believed, on CSF secretion, circulation and absorption. The volume and pressure changes in the newly developed CSF model, which by its anatomical dimensions and basic biophysical features imitates the craniospinal system in cats, are compared to those obtained on cats with and without the blockade of craniospinal communication in different body positions. During verticalization, a long-lasting occurrence of negative CSF pressure inside the cranium in animals with normal cranio-spinal communication was observed. CSF pressure gradients change depending on the body position, but those gradients do not enable unidirectional CSF circulation from the hypothetical site of secretion to the site of absorption in any of them. Thus, our results indicate the existence of new physiological/pathophysiological correlations between intracranial fluids, which opens up the possibility of new therapeutic approaches to intracranial hypertension.

The influence of body position on cerebrospinal fluid pressure gradient and movement in cats with normal and impaired craniospinal communication.

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Marijan Klarica

Full Text Available Intracranial hypertension is a severe therapeutic problem, as there is insufficient knowledge about the physiology of cerebrospinal fluid (CSF pressure. In this paper a new CSF pressure regulation hypothesis is proposed. According to this hypothesis, the CSF pressure depends on the laws of fluid mechanics and on the anatomical characteristics inside the cranial and spinal space, and not, as is today generally believed, on CSF secretion, circulation and absorption. The volume and pressure changes in the newly developed CSF model, which by its anatomical dimensions and basic biophysical features imitates the craniospinal system in cats, are compared to those obtained on cats with and without the blockade of craniospinal communication in different body positions. During verticalization, a long-lasting occurrence of negative CSF pressure inside the cranium in animals with normal cranio-spinal communication was observed. CSF pressure gradients change depending on the body position, but those gradients do not enable unidirectional CSF circulation from the hypothetical site of secretion to the site of absorption in any of them. Thus, our results indicate the existence of new physiological/pathophysiological correlations between intracranial fluids, which opens up the possibility of new therapeutic approaches to intracranial hypertension.

Improvised bubble continuous positive airway pressure

African Journals Online (AJOL)

PROF. EZECHUKWU

2014-08-15

Aug 15, 2014 ... Abstract: Background: Prematur- ity accounts for 25% of Neonatal mortality in Nigeria and Respira- tory Distress Syndrome is respon- sible for half of these deaths. Introducing continuous positive airway pressure for the treatment of RDS in Nigeria where health care financing is predominantly out-of-pocket ...

A sigmoidal fit for pressure-volume curves of idiopathic pulmonary fibrosis patients on mechanical ventilation: clinical implications

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Juliana C. Ferreira

2011-01-01

Full Text Available OBJECTIVE: Respiratory pressure-volume curves fitted to exponential equations have been used to assess disease severity and prognosis in spontaneously breathing patients with idiopathic pulmonary fibrosis. Sigmoidal equations have been used to fit pressure-volume curves for mechanically ventilated patients but not for idiopathic pulmonary fibrosis patients. We compared a sigmoidal model and an exponential model to fit pressure-volume curves from mechanically ventilated patients with idiopathic pulmonary fibrosis. METHODS: Six idiopathic pulmonary fibrosis patients and five controls underwent inflation pressure-volume curves using the constant-flow technique during general anesthesia prior to open lung biopsy or thymectomy. We identified the lower and upper inflection points and fit the curves with an exponential equation, V = A-B.e-k.P, and a sigmoid equation, V = a+b/(1+e-(P-c/d. RESULTS: The mean lower inflection point for idiopathic pulmonary fibrosis patients was significantly higher (10.5 ± 5.7 cm H2O than that of controls (3.6 ± 2.4 cm H2O. The sigmoidal equation fit the pressure-volume curves of the fibrotic and control patients well, but the exponential equation fit the data well only when points below 50% of the inspiratory capacity were excluded. CONCLUSION: The elevated lower inflection point and the sigmoidal shape of the pressure-volume curves suggest that respiratory system compliance is decreased close to end-expiratory lung volume in idiopathic pulmonary fibrosis patients under general anesthesia and mechanical ventilation. The sigmoidal fit was superior to the exponential fit for inflation pressure-volume curves of anesthetized patients with idiopathic pulmonary fibrosis and could be useful for guiding mechanical ventilation during general anesthesia in this condition.

Atmospheric pressure loading effects on Global Positioning System coordinate determinations

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Vandam, Tonie M.; Blewitt, Geoffrey; Heflin, Michael B.

1994-01-01

Earth deformation signals caused by atmospheric pressure loading are detected in vertical position estimates at Global Positioning System (GPS) stations. Surface displacements due to changes in atmospheric pressure account for up to 24% of the total variance in the GPS height estimates. The detected loading signals are larger at higher latitudes where pressure variations are greatest; the largest effect is observed at Fairbanks, Alaska (latitude 65 deg), with a signal root mean square (RMS) of 5 mm. Out of 19 continuously operating GPS sites (with a mean of 281 daily solutions per site), 18 show a positive correlation between the GPS vertical estimates and the modeled loading displacements. Accounting for loading reduces the variance of the vertical station positions on 12 of the 19 sites investigated. Removing the modeled pressure loading from GPS determinations of baseline length for baselines longer than 6000 km reduces the variance on 73 of the 117 baselines investigated. The slight increase in variance for some of the sites and baselines is consistent with expected statistical fluctuations. The results from most stations are consistent with approximately 65% of the modeled pressure load being found in the GPS vertical position measurements. Removing an annual signal from both the measured heights and the modeled load time series leaves this value unchanged. The source of the remaining discrepancy between the modeled and observed loading signal may be the result of (1) anisotropic effects in the Earth's loading response, (2) errors in GPS estimates of tropospheric delay, (3) errors in the surface pressure data, or (4) annual signals in the time series of loading and station heights. In addition, we find that using site dependent coefficients, determined by fitting local pressure to the modeled radial displacements, reduces the variance of the measured station heights as well as or better than using the global convolution sum.

Effect of changes in PCO2 and body positions on intraocular pressure during general anaesthesia.

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Hvidberg, A; Kessing, S V; Fernandes, A

1981-08-01

Elevated arterial carbon dioxide tension, induced by the administration of CO2 via the respiratory air or by hypoventilation, entailed a gradual increase in the IOP in patients without eye diseases under general anaesthesia. A sudden cessation of CO2 administration or hyperventilation caused such a rapid, simultaneous fall in IOP to values below the initial level that the pressure variations must be of vascular nature, presumably related to changes in choroidal blood volume. The above-mentioned procedures always cause a change in the central venous pressure (CVP) simultaneously with the IOP changes. Alterations of the CVP induced by hydrostatic factors in postural changes, placing the head 15 degrees above or below the horizontal level while keeping the PaCO2 constant, caused IOP changes of the same configuration and magnitude as described above. It is concluded, therefore, that presumably the CO2-conditioned IOP changes are due predominantly to changes in central venous pressure, being one link in a CO2-conditioned action upon the general circulation, entailing passive secondary changes in the choroidal venous blood volume and thereby an influence upon the IOP. On the basis of the present results it appears rational to recommend hyperventilation to keep the PaCO2 between 25 and 30 mm and a 15 degree anti-Trendelenburg position in operations on the eye under general anaesthesia, since both procedures afford a low central venous pressure and consequently a low pressure in the posterior segment of the eye, with its attendant advantages as regards vitreous complications and the insertion of intraocular lenses. Owing to the risk of an unacceptable fall in BP in the combined procedure, a frequent checking of the BP is needed.

Correlation between intra-abdominal pressure and pulmonary volumes after superior and inferior abdominal surgery

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Roberto de Cleva

2014-07-01

Full Text Available OBJECTIVE:Patients undergoing abdominal surgery are at risk for pulmonary complications. The principal cause of postoperative pulmonary complications is a significant reduction in pulmonary volumes (FEV1 and FVC to approximately 65-70% of the predicted value. Another frequent occurrence after abdominal surgery is increased intra-abdominal pressure. The aim of this study was to correlate changes in pulmonary volumes with the values of intra-abdominal pressure after abdominal surgery, according to the surgical incision in the abdomen (superior or inferior.METHODS:We prospectively evaluated 60 patients who underwent elective open abdominal surgery with a surgical time greater than 240 minutes. Patients were evaluated before surgery and on the 3rd postoperative day. Spirometry was assessed by maximal respiratory maneuvers and flow-volume curves. Intra-abdominal pressure was measured in the postoperative period using the bladder technique.RESULTS:The mean age of the patients was 56±13 years, and 41.6% 25 were female; 50 patients (83.3% had malignant disease. The patients were divided into two groups according to the surgical incision (superior or inferior. The lung volumes in the preoperative period showed no abnormalities. After surgery, there was a significant reduction in both FEV1 (1.6±0.6 L and FVC (2.0±0.7 L with maintenance of FEV1/FVC of 0.8±0.2 in both groups. The maximum intra-abdominal pressure values were similar (p= 0.59 for the two groups. There was no association between pulmonary volumes and intra-abdominal pressure measured in any of the groups analyzed.CONCLUSIONS:Our results show that superior and inferior abdominal surgery determines hypoventilation, unrelated to increased intra-abdominal pressure. Patients at high risk of pulmonary complications should receive respiratory care even if undergoing inferior abdominal surgery.

Correlation between intra-abdominal pressure and pulmonary volumes after superior and inferior abdominal surgery.

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Cleva, Roberto de; Assumpção, Marianna Siqueira de; Sasaya, Flavia; Chaves, Natalia Zuniaga; Santo, Marco Aurelio; Fló, Claudia; Lunardi, Adriana C; Jacob Filho, Wilson

2014-07-01

Patients undergoing abdominal surgery are at risk for pulmonary complications. The principal cause of postoperative pulmonary complications is a significant reduction in pulmonary volumes (FEV1 and FVC) to approximately 65-70% of the predicted value. Another frequent occurrence after abdominal surgery is increased intra-abdominal pressure. The aim of this study was to correlate changes in pulmonary volumes with the values of intra-abdominal pressure after abdominal surgery, according to the surgical incision in the abdomen (superior or inferior). We prospectively evaluated 60 patients who underwent elective open abdominal surgery with a surgical time greater than 240 minutes. Patients were evaluated before surgery and on the 3rd postoperative day. Spirometry was assessed by maximal respiratory maneuvers and flow-volume curves. Intra-abdominal pressure was measured in the postoperative period using the bladder technique. The mean age of the patients was 56 ± 13 years, and 41.6% 25 were female; 50 patients (83.3%) had malignant disease. The patients were divided into two groups according to the surgical incision (superior or inferior). The lung volumes in the preoperative period showed no abnormalities. After surgery, there was a significant reduction in both FEV1 (1.6 ± 0.6 L) and FVC (2.0 ± 0.7 L) with maintenance of FEV1/FVC of 0.8 ± 0.2 in both groups. The maximum intra-abdominal pressure values were similar (p=0.59) for the two groups. There was no association between pulmonary volumes and intra-abdominal pressure measured in any of the groups analyzed. Our results show that superior and inferior abdominal surgery determines hypoventilation, unrelated to increased intra-abdominal pressure. Patients at high risk of pulmonary complications should receive respiratory care even if undergoing inferior abdominal surgery.

Contrastive Analysis and Research on Negative Pressure Beam Tube System and Positive Pressure Beam Tube System for Mine Use

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Wang, Xinyi; Shen, Jialong; Liu, Xinbo

2018-01-01

Against the technical defects of universally applicable beam tube monitoring system at present, such as air suction in the beam tube, line clogging, long sampling time, etc., the paper analyzes the current situation of the spontaneous combustion fire disaster forecast of mine in our country and these defects one by one. On this basis, the paper proposes a research thought that improving the positive pressure beam tube so as to substitute the negative pressure beam tube. Then, the paper introduces the beam tube monitoring system based on positive pressure technology through theoretical analysis and experiment. In the comparison with negative pressure beam tube, the paper concludes the advantage of the new system and draws the conclusion that the positive pressure beam tube is superior to the negative pressure beam tube system both in test result and test time. At last, the paper proposes prospect of the beam tube monitoring system based on positive pressure technology.

Performance of current intensive care unit ventilators during pressure and volume ventilation.

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Marchese, Andrew D; Sulemanji, Demet; Chipman, Daniel; Villar, Jesús; Kacmarek, Robert M

2011-07-01

Intensive-care mechanical ventilators regularly enter the market, but the gas-delivery capabilities of many have never been assessed. We evaluated 6 intensive-care ventilators in the pressure support (PS), pressure assist/control (PA/C), and volume assist/control (VA/C) modes, with lung-model mechanics combinations of compliance and resistance of 60 mL/cm H(2)O and 10 cm H(2)O/L/s, 60 mL/cm H(2)O and 5 cm H(2)O/L/s, and 30 mL/cm H(2)O and 10 cm H(2)O/L/s, and inspiratory muscle effort of 5 and 10 cm H(2)O. PS and PA/C were set to 15 cm H(2)O, and PEEP to 5 and 15 cm H(2)O in all modes. During VA/C, tidal volume was set at 500 mL and inspiratory time was set at 0.8 second. Rise time and termination criteria were set at the manufacturers' defaults, and to an optimal level during PS and PA/C. There were marked differences in ventilator performance in all 3 modes. VA/C had the greatest difficulty meeting lung model demand and the greatest variability across all tested scenarios and ventilators. From high to low inspiratory muscle effort, pressure-to-trigger, time for pressure to return to baseline, and triggering pressure-time product decreased in all modes. With increasing resistance and decreasing compliance, tidal volume, pressure-to-trigger, time-to-trigger, time for pressure to return to baseline, time to 90% of peak pressure, and pressure-time product decreased. There were large differences between the default and optimal settings for all the variables in PS and PA/C. Performance was not affected by PEEP. Most of the tested ventilators performed at an acceptable level during the majority of evaluations, but some ventilators performed inadequately during specific settings. Bedside clinical evaluation is needed.

Experimental evidence for negative turgor pressure in small leaf cells of Robinia pseudoacacia L versus large cells of Metasequoia glyptostroboides Hu et W.C. Cheng. 2. Höfler diagrams below the volume of zero turgor and the theoretical implication for pressure-volume curves of living cells.

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Yang, Dongmei; Li, Junhui; Ding, Yiting; Tyree, Melvin T

2017-03-01

The physiological advantages of negative turgor pressure, P t , in leaf cells are water saving and homeostasis of reactants. This paper advances methods for detecting the occurrence of negative P t in leaves. Biomechanical models of pressure-volume (PV) curves predict that negative P t does not change the linearity of PV curve plots of inverse balance pressure, P B , versus relative water loss, but it does predict changes in either the y-intercept or the x-intercept of the plots depending on where cell collapse occurs in the P B domain because of negative P t . PV curve analysis of Robinia leaves revealed a shift in the x-intercept (x-axis is relative water loss) of PV curves, caused by negative P t of palisade cells. The low x-intercept of the PV curve was explained by the non-collapse of palisade cells in Robinia in the P B domain. Non-collapse means that P t smoothly falls from positive to negative values with decreasing cell volume without a dramatic change in slope. The magnitude of negative turgor in non-collapsing living cells was as low as -1.3 MPa and the relative volume of the non-collapsing cell equaled 58% of the total leaf cell volume. This study adds to the growing evidence for negative P t . © 2016 John Wiley & Sons Ltd.

Low tidal volume and high positive end-expiratory pressure mechanical ventilation results in increased inflammation and ventilator-associated lung injury in normal lungs.

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Hong, Caron M; Xu, Da-Zhong; Lu, Qi; Cheng, Yunhui; Pisarenko, Vadim; Doucet, Danielle; Brown, Margaret; Aisner, Seena; Zhang, Chunxiang; Deitch, Edwin A; Delphin, Ellise

2010-06-01

Protective mechanical ventilation with low tidal volume (Vt) and low plateau pressure reduces mortality and decreases the length of mechanical ventilation in patients with acute respiratory distress syndrome. Mechanical ventilation that will protect normal lungs during major surgical procedures of long duration may improve postoperative outcomes. We performed an animal study comparing 3 ventilation strategies used in the operating room in normal lungs. We compared the effects on pulmonary mechanics, inflammatory mediators, and lung tissue injury. Female pigs were randomized into 3 groups. Group H-Vt/3 (n = 6) was ventilated with a Vt of 15 mL/kg predicted body weight (PBW)/positive end-expiratory pressure (PEEP) of 3 cm H(2)O, group L-Vt/3 (n = 6) with a Vt of 6 mL/kg PBW/PEEP of 3 cm H(2)O, and group L-Vt/10 (n = 6) with a Vt of 6 mL/kg PBW/PEEP of 10 cm H(2)O, for 8 hours. Hemodynamics, airway mechanics, arterial blood gases, and inflammatory markers were monitored. Bronchoalveolar lavage (BAL) was analyzed for inflammatory markers and protein concentration. The right lower lobe was assayed for mRNA of specific cytokines. The right lower lobe and right upper lobe were evaluated histologically. In contrast to groups H-Vt/3 and L-Vt/3, group L-Vt/10 exhibited a 6-fold increase in inflammatory mediators in BAL (P ventilation with high PEEP resulted in increased production of inflammatory markers. Low PEEP resulted in lower levels of inflammatory markers. High Vt/low PEEP resulted in less histologic lung injury.

Correlation between orbital volume, body mass index, and eyeball position in healthy East asians.

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Yoo, Jun Ho; Lee, Young Hen; Lee, Hwa; Kim, Jung Wan; Chang, Minwook; Park, Minsoo; Baek, Sehyun

2013-05-01

The objectives of this study were measure the orbital volume of healthy Koreans and analyze the differences between orbital tissue volume with respect to age and sex and to assess any correlation between body mass index (BMI), eyeball position, and orbital volume. We retrospectively evaluated the scan results of patients who had undergone orbital computed tomography scans between November 2010 and November 2011. We assessed the scan results of 184 orbits in 92 adults who had no pathology of the orbit. The individuals were classified into 3 groups with respect to age. Orbital volume, effective orbital volume (defined as the difference between orbital and eyeball volume), extraocular muscle volume, orbital fat volume, and transverse globe protrusion were recorded and analyzed. The records of the subjects were reviewed retrospectively, and BMI was calculated. A correlation analysis was performed to investigate the correlation between BMI, eyeball position, and orbital volume. Orbital tissue volume, with the exception of orbital fat volume, was larger in men compared with women. In both sexes, orbital fat volume increased with increasing age, whereas the other volumes decreased. Orbital tissue volumes increased with increasing BMI, but transverse globe protrusion was not significantly related to BMI. In addition, orbital volume and effective orbital volume were positively correlated with transverse globe protrusion. These results provide basic information about the effects of age, sex, and BMI on orbital volume and eyeball position in healthy Koreans. Furthermore, these results will be helpful in the diagnosis of orbital diseases and in planning orbital surgeries.

High speed analysis of high pressure combustion in a constant volume cell

NARCIS (Netherlands)

Frijters, P.J.M.; Klein-Douwel, R.J.H.; Manski, S.S.; Somers, L.M.T.; Baert, R.S.G.; Dias, V.

2005-01-01

A combustion process with N2, O2 and C2H4 as fuel used in an opticallyaccessible, high pressure, high temperature, constant volume cell forresearch on diesel fuel spray formation, is studied. The flame frontspeed Vf,HS is determined using high speed imaging. The pressure traceof the combustion

Use of dynamic CT in acute respiratory distress syndrome (ARDS) with comparison of positive and negative pressure ventilation

Energy Technology Data Exchange (ETDEWEB)

Helm, Emma; Babyn, Paul [Hospital for Sick Children, Department of Diagnostic Imaging, Toronto (Canada); Talakoub, Omid; Alirezaie, Javad [Ryerson University, Department of Electrical and Computer Engineering, Toronto, ON (Canada); Grasso, Francesco; Engelberts, Doreen; Kavanagh, Brian P. [Hospital for Sick Children and the University of Toronto, Departments of Anesthesia and Critical Care Medicine and the Program in Pulmonary and Experimental Medicine, Toronto (Canada)

2009-01-15

Negative pressure ventilation via an external device ('iron lung') has the potential to provide better oxygenation with reduced barotrauma in patients with ARDS. This study was designed to see if oxygenation differences between positive and negative ventilation could be explained by CT. Six anaesthetized rabbits had ARDS induced by repeated saline lavage. Rabbits were ventilated with positive pressure ventilation (PPV) and negative pressure ventilation (NPV) in turn. Dynamic CT images were acquired over the respiratory cycle. A computer-aided method was used to segment the lung and calculate the range of CT densities within each slice. Volumes of ventilated lung and atelectatic lung were measured over the respiratory cycle. NPV was associated with an increased percentage of ventilated lung and decreased percentage of atelectatic lung. The most significant differences in ventilation and atelectasis were seen at mid-inspiration and mid-expiration (ventilated lung NPV=61%, ventilated lung PPV=47%, p<0.001; atelectatic lung NPV=10%, atelectatic lung PPV 19%, p<0.001). Aeration differences were not significant at end-inspiration. Dynamic CT can show differences in lung aeration between positive and negative ventilation in ARDS. These differences would not be appreciated if only static breath-hold CT was used. (orig.)

Experimental determination of the drywell volume: 1/5 scale pressure suppression test

International Nuclear Information System (INIS)

Pitts, J.H.

1977-01-01

The BWR Mk 1 1/5 scale drywell volume, including space in all ports up to the first flange, was experimentally determined to be 10.01 m 3 with an uncertainty of +- 0.03 m 3 . The method of measurement used a 0.040879 m 3 calibrated volume that was initially filled with helium to 36.5 MPa. The calibrated volume was then connected to the drywell and the pressures equalized. The volumes of the vent pipes, instrumentation ports, and either the steam inlet or nitrogen inlet were subtracted from the measured drywell volume to obtain the net active drywell volume. The net active drywell volume is 9.87 m 3 for air tests and 9.85 m 3 for steam tests

The study of alteration in left ventricular volume and pressure to volume ratio during exercise in patients with coronary heart disease

International Nuclear Information System (INIS)

Liu Zhonglin; Pei Zhuguo; Zang Bin

1994-01-01

The alterations induced by exercise in left ventricular end diastolic volume index (EDVI), end systolic volume index (ESVI) and systolic blood pressure to end systolic volume ratio (P/ESV) were studied in 15 normal subjects and 42 patients with coronary heart disease using a non-geometric count-based method and supine bicycle exercise test. Normal subjects had an increase in EDVI and a decrease in ESVI, but coronary heart disease patients had an increase in both EDVI and ESVI. The extent of increase induced by exercise in EDVI was greater in angina patients than that in normal and old myocardial infarction subjects. The P/ESV can be used to evaluate left ventricular systolic pressure-volume relationship. For the P/ESV exercise response, the sensitivity, specificity and accuracy for coronary heart disease were 95%, 93% and 95%, respectively

PIEZOELECTRIC WAVEGUIDE SENSOR FOR MEASURING PULSE PRESSURE IN CLOSED LIQUID VOLUMES AT HIGH VOLTAGE ELECTRIC DISCHARGE

Directory of Open Access Journals (Sweden)

V. G. Zhekul

2017-10-01

Full Text Available Purpose. Investigations of the characteristics of pressure waves presuppose the registration of the total profile of the pressure wave at a given point in space. For these purposes, various types of «pressure to the electrical signal» transmitters (sensors are used. Most of the common sensors are unsuitable for measuring the pulse pressure in a closed water volume at high hydrostatic pressures, in particular to study the effect of a powerful high-voltage pulse discharge on increasing the inflow of minerals and drinking water in wells. The purpose of the work was to develop antijamming piezoelectric waveguide sensor for measuring pulse pressure at a close distance from a high-voltage discharge channel in a closed volume of a liquid. Methodology. We have applied the calibration method as used as a secondary standard, the theory of electrical circuits. Results. We have selected the design and the circuit solution of the waveguide pressure sensor. We have developed a waveguide pulse-pressure sensor DTX-1 with a measuring loop. This sensor makes it possible to study the spectral characteristics of pressure waves of high-voltage pulse discharge in closed volumes of liquid at a hydrostatic pressure of up to 20 MPa and a temperature of up to 80 °C. The sensor can be used to study pressure waves with a maximum amplitude value of up to 150 MPa and duration of up to 80 µs. According to the results of the calibration, the sensitivity of the developed sensor DTX-1 with a measuring loop is 0.0346 V/MPa. Originality. We have further developed the theory of designing the waveguide piezoelectric pulse pressure sensors for measuring the pulse pressure at a close distance from a high-voltage discharge channel in a closed fluid volume by controlling the attenuation of the amplitude of the pressure signal. Practical value. We have developed, created, calibrated, used in scientific research waveguide pressure pulse sensors DTX-1. We propose sensors DTX-1 for sale

Are tidal volume measurements in neonatal pressure-controlled ventilation accurate?

Science.gov (United States)

Chow, Lily C; Vanderhal, Andre; Raber, Jorge; Sola, Augusto

2002-09-01

Bedside pulmonary mechanics monitors (PMM) have become useful in ventilatory management in neonates. These monitors are used more frequently due to recent improvements in data-processing capabilities. PMM devices are often part of the ventilator or are separate units. The accuracy and reliability of these systems have not been carefully evaluated. We compared a single ventilatory parameter, tidal volume (V(t)), as measured by several systems. We looked at two freestanding PMMs: the Ventrak Respiratory Monitoring System (Novametrix, Wallingford, CT) and the Bicore CP-100 Neonatal Pulmonary Monitor (Allied Health Care Products, Riverside, CA), and three ventilators with built-in PMM: the VIP Bird Ventilator (Bird Products Corp., Palm Springs, CA), Siemens Servo 300A (Siemens-Elema AB, Solna, Sweden), and Drager Babylog 8000 (Drager, Inc., Chantilly, VA). A calibrated syringe (Hans Rudolph, Inc., Kansas City, MO) was used to deliver tidal volumes of 4, 10, and 20 mL to each ventilator system coupled with a freestanding PMM. After achieving steady state, six consecutive V(t) readings were taken simultaneously from the freestanding PMM and each ventilator. In a second portion of the bench study, we used pressure-control ventilation and measured exhaled tidal volume (V(te)) while ventilating a Bear Test Lung with the same three ventilators. We adjusted peak inspiratory pressure (PIP) under controlled conditions to achieve the three different targeted tidal volumes on the paired freestanding PMM. Again, six V(te) measurements were recorded for each tidal volume. Means and standard deviations were calculated.The percentage difference in measurement of V(t) delivered by calibrated syringe varied greatly, with the greatest discrepancy seen in the smallest tidal volumes, by up to 28%. In pressure control mode, V(te) as measured by the Siemens was significantly overestimated by 20-95%, with the biggest discrepancy at the smallest V(te), particularly when paired with the Bicore

Does the Position or Contact Pressure of the Stethoscope Make Any Difference to Clinical Blood Pressure Measurements

Science.gov (United States)

Pan, Fan; Zheng, Dingchang; He, Peiyu; Murray, Alan

2014-01-01

Abstract This study aimed to investigate the effect of stethoscope position and contact pressure on auscultatory blood pressure (BP) measurement. Thirty healthy subjects were studied. Two identical stethoscopes (one under the cuff, the other outside the cuff) were used to simultaneously and digitally record 2 channels of Korotkoff sounds during linear cuff pressure deflation. For each subject, 3 measurements with different contact pressures (0, 50, and 100 mm Hg) on the stethoscope outside the cuff were each recorded at 3 repeat sessions. The Korotkoff sounds were replayed twice on separate days to each of 2 experienced listeners to determine systolic and diastolic BPs (SBP and DBP). Variance analysis was performed to study the measurement repeatability and the effect of stethoscope position and contact pressure on BPs. There was no significant BP difference between the 3 repeat sessions, between the 2 determinations from each listener, between the 2 listeners and between the 3 stethoscope contact pressures (all P > 0.06). There was no significant SBP difference between the 2 stethoscope positions at the 2 lower stethoscope pressures (P = 0.23 and 0.45), but there was a small (0.4 mm Hg, clinically unimportant) significant difference (P = 0.005) at the highest stethoscope pressure. The key result was that, DBP from the stethoscope under the cuff was significantly lower than that from outside the cuff by 2.8 mm Hg (P stethoscope outside the cuff, tends to give a higher DBP than the true intra-arterial pressure, this study could suggest that the stethoscope position under the cuff, and closer to the arterial occlusion, might yield measurements closer to the actual invasive DBP. PMID:25546675

Relationship between pulmonary artery volumes at computed tomography and pulmonary artery pressures in patients with- and without pulmonary hypertension

Energy Technology Data Exchange (ETDEWEB)

Froelich, Jens J. [Department of Radiology, Philipps-University Hospital, Baldingerstrasse, 35043 Marburg (Germany)], E-mail: jens.froelich@klinikum-hef.de; Koenig, Helmut [Department of Radiology, Philipps-University Hospital, Baldingerstrasse, 35043 Marburg (Germany)], E-mail: helmut.koenig@siemens.com; Knaak, Lennard [Department of Medicine, Philipps-University Hospital, Baldingerstrasse, 35043 Marburg (Germany)], E-mail: froehlic@staff.uni-marburg.de; Krass, Stefan [MeVis Research, Universitaetsallee 29, 28359 Bremen (Germany)], E-mail: krass@mevis.de; Klose, Klaus J. [Department of Radiology, Philipps-University Hospital, Baldingerstrasse, 35043 Marburg (Germany)], E-mail: klose@med.uni-marburg.de

2008-09-15

Objectives: This study was designed to determine the relationship between pulmonary artery (PA) volumes at computed tomography (CT) and PA pressures at right-sided heart catheterization in patients with and without pulmonary hypertension (PAH) to develop a noninvasive CT method of PA pressure quantification. Materials and methods: Sixteen patients with chronic sleep apnea syndrome underwent contrast enhanced helical CT (slice thickness 3 mm; pitch 2; increment 2 mm) at inspiration. Eight patients had PAH while cardiopulmonary disease has been excluded in eight other patients. Vascular volumes were determined using a 3D technique (threshold seeded vascular tracing algorithm; thresholds -600 H [lower] and 3000 H [upper]). Right-sided heart catheterization measurements were available for linear regression analysis of PA volumes and pressures. Results: Correlation between PA pressures and volumes (normalized for BMI), was high in both groups (without PAH: r = .85; with PAH .90, Pearson). Compared to elevated PA pressures in patients with pulmonary hypertension (p < .005), PA volumes also were significantly increased (p < .05) among the groups. Conclusions: High correlation was found between PA volumes and mean PA pressures in patients with- and without PAH. Significant differences in PA volumes at CT-volumetry may admit non-invasive determination of pulmonary hypertension.

Relationship between pulmonary artery volumes at computed tomography and pulmonary artery pressures in patients with- and without pulmonary hypertension

International Nuclear Information System (INIS)

Froelich, Jens J.; Koenig, Helmut; Knaak, Lennard; Krass, Stefan; Klose, Klaus J.

2008-01-01

Objectives: This study was designed to determine the relationship between pulmonary artery (PA) volumes at computed tomography (CT) and PA pressures at right-sided heart catheterization in patients with and without pulmonary hypertension (PAH) to develop a noninvasive CT method of PA pressure quantification. Materials and methods: Sixteen patients with chronic sleep apnea syndrome underwent contrast enhanced helical CT (slice thickness 3 mm; pitch 2; increment 2 mm) at inspiration. Eight patients had PAH while cardiopulmonary disease has been excluded in eight other patients. Vascular volumes were determined using a 3D technique (threshold seeded vascular tracing algorithm; thresholds -600 H [lower] and 3000 H [upper]). Right-sided heart catheterization measurements were available for linear regression analysis of PA volumes and pressures. Results: Correlation between PA pressures and volumes (normalized for BMI), was high in both groups (without PAH: r = .85; with PAH .90, Pearson). Compared to elevated PA pressures in patients with pulmonary hypertension (p < .005), PA volumes also were significantly increased (p < .05) among the groups. Conclusions: High correlation was found between PA volumes and mean PA pressures in patients with- and without PAH. Significant differences in PA volumes at CT-volumetry may admit non-invasive determination of pulmonary hypertension

Branching of positive discharge streamers in air at varying pressures

NARCIS (Netherlands)

Briels, T.M.P.; Veldhuizen, van E.M.; Ebert, U.M.

2005-01-01

The formation of positive streamers in a 17-mm gap in air is studied at pressures varying in the range from 1010 to 100 mbar. An intensified charge coupled device camera is used to image the discharge. At high pressures, the discharge shows many branches, while at low pressure, fewer branches arise.

Ice Ih anomalies: Thermal contraction, anomalous volume isotope effect, and pressure-induced amorphization

Science.gov (United States)

Salim, Michael A.; Willow, Soohaeng Yoo; Hirata, So

2016-05-01

Ice Ih displays several anomalous thermodynamic properties such as thermal contraction at low temperatures, an anomalous volume isotope effect (VIE) rendering the volume of D2O ice greater than that of H2O ice, and a pressure-induced transition to the high-density amorphous (HDA) phase. Furthermore, the anomalous VIE increases with temperature, despite its quantum-mechanical origin. Here, embedded-fragment ab initio second-order many-body perturbation (MP2) theory in the quasiharmonic approximation (QHA) is applied to the Gibbs energy of an infinite, proton-disordered crystal of ice Ih at wide ranges of temperatures and pressures. The quantum effect of nuclei moving in anharmonic potentials is taken into account from first principles without any empirical or nonsystematic approximation to either the electronic or vibrational Hamiltonian. MP2 predicts quantitatively correctly the thermal contraction at low temperatures, which is confirmed to originate from the volume-contracting hydrogen-bond bending modes (acoustic phonons). It qualitatively reproduces (but underestimates) the thermal expansion at higher temperatures, caused by the volume-expanding hydrogen-bond stretching (and to a lesser extent librational) modes. The anomalous VIE is found to be the result of subtle cancellations among closely competing isotope effects on volume from all modes. Consequently, even ab initio MP2 with the aug-cc-pVDZ and aug-cc-pVTZ basis sets has difficulty reproducing this anomaly, yielding qualitatively varied predictions of the sign of the VIE depending on such computational details as the choice of the embedding field. However, the temperature growth of the anomalous VIE is reproduced robustly and is ascribed to the librational modes. These solid-state MP2 calculations, as well as MP2 Born-Oppenheimer molecular dynamics, find a volume collapse and a loss of symmetry and long-range order in ice Ih upon pressure loading of 2.35 GPa or higher. Concomitantly, rapid softening of

Ice Ih anomalies: Thermal contraction, anomalous volume isotope effect, and pressure-induced amorphization

Energy Technology Data Exchange (ETDEWEB)

Salim, Michael A.; Willow, Soohaeng Yoo; Hirata, So, E-mail: sohirata@illinois.edu [Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801 (United States)

2016-05-28

Ice Ih displays several anomalous thermodynamic properties such as thermal contraction at low temperatures, an anomalous volume isotope effect (VIE) rendering the volume of D{sub 2}O ice greater than that of H{sub 2}O ice, and a pressure-induced transition to the high-density amorphous (HDA) phase. Furthermore, the anomalous VIE increases with temperature, despite its quantum-mechanical origin. Here, embedded-fragment ab initio second-order many-body perturbation (MP2) theory in the quasiharmonic approximation (QHA) is applied to the Gibbs energy of an infinite, proton-disordered crystal of ice Ih at wide ranges of temperatures and pressures. The quantum effect of nuclei moving in anharmonic potentials is taken into account from first principles without any empirical or nonsystematic approximation to either the electronic or vibrational Hamiltonian. MP2 predicts quantitatively correctly the thermal contraction at low temperatures, which is confirmed to originate from the volume-contracting hydrogen-bond bending modes (acoustic phonons). It qualitatively reproduces (but underestimates) the thermal expansion at higher temperatures, caused by the volume-expanding hydrogen-bond stretching (and to a lesser extent librational) modes. The anomalous VIE is found to be the result of subtle cancellations among closely competing isotope effects on volume from all modes. Consequently, even ab initio MP2 with the aug-cc-pVDZ and aug-cc-pVTZ basis sets has difficulty reproducing this anomaly, yielding qualitatively varied predictions of the sign of the VIE depending on such computational details as the choice of the embedding field. However, the temperature growth of the anomalous VIE is reproduced robustly and is ascribed to the librational modes. These solid-state MP2 calculations, as well as MP2 Born–Oppenheimer molecular dynamics, find a volume collapse and a loss of symmetry and long-range order in ice Ih upon pressure loading of 2.35 GPa or higher. Concomitantly, rapid

Influence of pressure on the properties of chromatographic columns. II. The column hold-up volume.

Science.gov (United States)

Gritti, Fabrice; Martin, Michel; Guiochon, Georges

2005-04-08

The effect of the local pressure and of the average column pressure on the hold-up column volume was investigated between 1 and 400 bar, from a theoretical and an experimental point of view. Calculations based upon the elasticity of the solids involved (column wall and packing material) and the compressibility of the liquid phase show that the increase of the column hold-up volume with increasing pressure that is observed is correlated with (in order of decreasing importance): (1) the compressibility of the mobile phase (+1 to 5%); (2) in RPLC, the compressibility of the C18-bonded layer on the surface of the silica (+0.5 to 1%); and (3) the expansion of the column tube (columns packed with the pure Resolve silica (0% carbon), the derivatized Resolve-C18 (10% carbon) and the Symmetry-C18 (20% carbon) adsorbents, using water, methanol, or n-pentane as the mobile phase. These solvents have different compressibilities. However, 1% of the relative increase of the column hold-up volume that was observed when the pressure was raised is not accounted for by the compressibilities of either the solvent or the C18-bonded phase. It is due to the influence of the pressure on the retention behavior of thiourea, the compound used as tracer to measure the hold-up volume.

The vascular basis of the positional influence of the intraocular pressure.

Science.gov (United States)

Krieglstein, G K; Waller, W K; Leydhecker, W

1978-05-02

By measuring intraocular pressure in different body positions from 60 degrees semiupright to 30 degrees head down, a nonlinear relationship between IOP increase and body position was confirmed. IOP postural response in individual subjects was roughly correlated to ophthalmic arterial pressure and to the episcleral venous pressure postural response. In one series of subjects, the episcleral venous pressure increments due to posture wa; parallel to the applanation-indentation disparity in the same individual eyes. Differential tonometry with applanation or indentation procedures under blind conditions gave significantly low indentation readings. It is concluded that IOP postural response depends on arterial and venous vascular changes when subjects move from an erect to a horizontal body position. Blood expulsion from the choroid by indentation tonometry might be the reason that this tonometric procedure does not measure IOP changes based on vascular changes.

Effects of positive end-expiratory pressure on renal function.

Science.gov (United States)

Järnberg, P O; de Villota, E D; Eklund, J; Granberg, P O

1978-01-01

The effects were studied positive end-expiratory pressure (PEEP) on renal function in eight patients with acute respiratory failure, requiring mechanical ventilation. On application of PEEP + 10 cm H2O, central venous pressure increased, systolic blood pressure decreased, urine flow and PAH-clearance were reduced, while inulin clearance remained stable. There was a marked increase in fractional sodium reabsorption and a concurrent decrease in fractional osmolal excretion. Fractional free-water clearance and the ratio UOsm/POsm did change.

Assessing intravascular volume by difference in pulse pressure in pigs submitted to graded hemorrhage.

Science.gov (United States)

Pestel, Gunther J; Hiltebrand, Luzius B; Fukui, Kimiko; Cohen, Delphine; Hager, Helmut; Kurz, Andrea M

2006-10-01

We assessed changes in intravascular volume monitored by difference in pulse pressure (dPP%) after stepwise hemorrhage in an experimental pig model. Six pigs (23-25 kg) were anesthetized (isoflurane 1.5 vol%) and mechanically ventilated to keep end-tidal CO2 (etCO2) at 35 mmHg. A PA-catheter and an arterial catheter were placed via femoral access. During and after surgery, animals received lactated Ringer's solution as long as they were considered volume responders (dPP>13%). Then animals were allowed to stabilize from the induction of anesthesia and insertion of catheters for 30 min. After stabilization, baseline measurements were taken. Five percent of blood volume was withdrawn, followed by another 5%, and then in 10%-increments until death from exsanguination occurred. After withdrawal of 5% of blood volume, all pigs were considered volume responders (dPP>13%); dPP rose significantly from 6.1+/-3.3% to 19.4+/-4.2%. The regression analysis of stepwise hemorrhage revealed a linear relation between blood loss (hemorrhage in %) and dPP (y=0.99*x+14; R2=0.7764; P<.0001). In addition, dPP was the only parameter that changed significantly between baseline and a blood loss of 5% (P<0.01), whereas cardiac output, stroke volume, heart rate, MAP, central venous pressure, pulmonary artery occlusion pressure, and systemic vascular resistance, respectively, remained unchanged. We conclude that in an experimental hypovolemic pig model, dPP correlates well with blood loss.

Nonlinear isochrones in murine left ventricular pressure-volume loops: how well does the time-varying elastance concept hold?

Science.gov (United States)

Claessens, T E; Georgakopoulos, D; Afanasyeva, M; Vermeersch, S J; Millar, H D; Stergiopulos, N; Westerhof, N; Verdonck, P R; Segers, P

2006-04-01

The linear time-varying elastance theory is frequently used to describe the change in ventricular stiffness during the cardiac cycle. The concept assumes that all isochrones (i.e., curves that connect pressure-volume data occurring at the same time) are linear and have a common volume intercept. Of specific interest is the steepest isochrone, the end-systolic pressure-volume relationship (ESPVR), of which the slope serves as an index for cardiac contractile function. Pressure-volume measurements, achieved with a combined pressure-conductance catheter in the left ventricle of 13 open-chest anesthetized mice, showed a marked curvilinearity of the isochrones. We therefore analyzed the shape of the isochrones by using six regression algorithms (two linear, two quadratic, and two logarithmic, each with a fixed or time-varying intercept) and discussed the consequences for the elastance concept. Our main observations were 1) the volume intercept varies considerably with time; 2) isochrones are equally well described by using quadratic or logarithmic regression; 3) linear regression with a fixed intercept shows poor correlation (R(2) volume intercept of the ESPVR. In conclusion, the linear time-varying elastance fails to provide a sufficiently robust model to account for changes in pressure and volume during the cardiac cycle in the mouse ventricle. A new framework accounting for the nonlinear shape of the isochrones needs to be developed.

Continuous positive airway pressure: Physiology and comparison of devices.

Science.gov (United States)

Gupta, Samir; Donn, Steven M

2016-06-01

Nasal continuous positive airway pressure (CPAP) is increasingly used for respiratory support in preterm babies at birth and after extubation from mechanical ventilation. Various CPAP devices are available for use that can be broadly grouped into continuous flow and variable flow. There are potential physiologic differences between these CPAP systems and the choice of a CPAP device is too often guided by individual expertise and experience rather than by evidence. When interpreting the evidence clinicians should take into account the pressure generation sources, nasal interface, and the factors affecting the delivery of pressure, such as mouth position and respiratory drive. With increasing use of these devices, better monitoring techniques are required to assess the efficacy and early recognition of babies who are failing and in need of escalated support. Copyright © 2016 Elsevier Ltd. All rights reserved.

Thermodynamics of aqueous methyldiethanolamine (MDEA) and methyldiethanolammonium chloride (MDEAH+Cl-) over a wide range of temperature and pressure: Apparent molar volumes, heat capacities, and isothermal compressibilities

International Nuclear Information System (INIS)

Hawrylak, B.; Palepu, R.; Tremaine, Peter R.

2006-01-01

Apparent molar volumes of aqueous methyldiethanolamine and its salt were determined with platinum vibrating tube densitometers over a range of temperatures from 283K= o , heat capacities C p o , and isothermal compressibilities κ T o . The standard partial molar volumes V o for the neutral amine and its salt show increasingly positive and negative values, respectively, at high temperatures and pressures, as predicted by corresponding states and group additivity arguments. The density model and the revised Helgeson-Kirkham-Flowers (HKF) model have been used to represent the temperature and pressure dependence of the standard partial molar properties to yield a full thermodynamic description of the system

Severe bronchopulmonary dysplasia improved by noninvasive positive pressure ventilation: a case report

Directory of Open Access Journals (Sweden)

Mann Christian

2011-09-01

Full Text Available Abstract Introduction This is the first report to describe the feasibility and effectiveness of noninvasive positive pressure ventilation in the secondary treatment of bronchopulmonary dysplasia. Case presentation A former male preterm of Caucasian ethnicity delivered at 29 weeks gestation developed severe bronchopulmonary dysplasia. At the age of six months he was in permanent tachypnea and dyspnea and in need of 100% oxygen with a flow of 2.0 L/minute via a nasal cannula. Intermittent nocturnal noninvasive positive pressure ventilation was then administered for seven hours daily. The ventilator was set at a positive end-expiratory pressure of 6 cmH2O, with pressure support of 4 cmH2O, trigger at 1.4 mL/second, and a maximum inspiratory time of 0.7 seconds. Over the course of seven weeks, the patient's maximum daytime fraction of inspired oxygen via nasal cannula decreased from 1.0 to 0.75, his respiratory rate from 64 breaths/minute to 50 breaths/minute and carbon dioxide from 58 mmHg to 44 mmHg. Conclusion Noninvasive positive pressure ventilation may be a novel therapeutic option for established severe bronchopulmonary dysplasia. In the case presented, noninvasive positive pressure ventilation achieved sustained improvement in ventilation and thus prepared our patient for safe home oxygen therapy.

Respiratory System Mechanics During Low Versus High Positive End-Expiratory Pressure in Open Abdominal Surgery: A Substudy of PROVHILO Randomized Controlled Trial.

Science.gov (United States)

D'Antini, Davide; Huhle, Robert; Herrmann, Jacob; Sulemanji, Demet S; Oto, Jun; Raimondo, Pasquale; Mirabella, Lucia; Hemmes, Sabrine N T; Schultz, Marcus J; Pelosi, Paolo; Kaczka, David W; Vidal Melo, Marcos Francisco; Gama de Abreu, Marcelo; Cinnella, Gilda

2018-01-01

In the 2014 PROtective Ventilation using HIgh versus LOw positive end-expiratory pressure (PROVHILO) trial, intraoperative low tidal volume ventilation with high positive end-expiratory pressure (PEEP = 12 cm H2O) and lung recruitment maneuvers did not decrease postoperative pulmonary complications when compared to low PEEP (0-2 cm H2O) approach without recruitment breaths. However, effects of intraoperative PEEP on lung compliance remain poorly understood. We hypothesized that higher PEEP leads to a dominance of intratidal overdistension, whereas lower PEEP results in intratidal recruitment/derecruitment (R/D). To test our hypothesis, we used the volume-dependent elastance index %E2, a respiratory parameter that allows for noninvasive and radiation-free assessment of dominant overdistension and intratidal R/D. We compared the incidence of intratidal R/D, linear expansion, and overdistension by means of %E2 in a subset of the PROVHILO cohort. In 36 patients from 2 participating centers of the PROVHILO trial, we calculated respiratory system elastance (E), resistance (R), and %E2, a surrogate parameter for intratidal overdistension (%E2 > 30%) and R/D (%E2 mechanical ventilation with protective tidal volumes in patients undergoing open abdominal surgery, lung recruitment followed by PEEP of 12 cm H2O decreased the incidence of intratidal R/D and did not worsen overdistension, when compared to PEEP ≤2 cm H2O.

Generation of tidal volume via gentle chest pressure in children over one year old.

Science.gov (United States)

Tsui, Ban C H; Horne, Sara; Tsui, Jenkin; Corry, Gareth N

2015-07-01

In the event of cardiac arrest, cardiopulmonary resuscitation (CPR) is a well-established technique to maintain oxygenation of tissues and organs until medical equipment and staff are available. During CPR, chest compressions help circulate blood and have been shown in animal models to be a means of short-term oxygenation. In this study, we tested whether gentle chest pressure can generate meaningful tidal volume in paediatric subjects. This prospective cohort pilot study recruited children under the age of 17 years and undergoing any surgery requiring general anaesthetic and endotracheal intubation. After induction of general anaesthesia, tidal volumes were obtained before and after intubation by applying a downward force on the chest which was not greater than the patient's weight. Mean tidal volumes were compared for unprotected versus protected airway and for type of surgery. Mean tidal volume generated with an unprotected and protected airway was 2.7 (1.7) and 2.9 (2.3) mL/kg, respectively. Mean tidal volume generated with mechanical ventilation was 13.6 (4.9) mL/kg. No statistical significance was found when comparing tidal volumes generated with an unprotected or protected airway (p = 0.20), type of surgery (tonsillectomy and/or adenoidectomy versus other surgery) (unprotected, p = 0.09; protected, p = 0.37), and when age difference between groups was taken into account (p = 0.34). Using gentle chest pressure, we were able to generate over 20% of the tidal volume achieved with mechanical ventilation. Our results suggest that gentle chest pressure may be a means to support temporary airflow in children. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Continuous Positive Airway Pressure Strategies with Bubble Nasal Continuous Positive Airway Pressure: Not All Bubbling Is the Same: The Seattle Positive Airway Pressure System.

Science.gov (United States)

Welty, Stephen E

2016-12-01

Premature neonates are predisposed to complications, including bronchopulmonary dysplasia (BPD). BPD is associated with long-term pulmonary and neurodevelopmental consequences. Noninvasive respiratory support with nasal continuous positive airway pressure (CPAP) has been recommended strongly by the American Academy of Pediatrics. However, CPAP implementation has shown at least a 50% failure rate. Enhancing nasal CPAP effectiveness may decrease the need for mechanical ventilation and reduce the incidence of BPD. Bubble nasal CPAP is better than nasal CPAP using mechanical devices and the bubbling provides air exchange in distal respiratory units. The Seattle PAP system reduces parameters that assess work of breathing. Copyright © 2016 Elsevier Inc. All rights reserved.

Respiratory Pattern and Tidal Volumes Differ for Pressure Support and Volume-assured Pressure Support in Amyotrophic Lateral Sclerosis.

Science.gov (United States)

Nicholson, Trevor T; Smith, Sean B; Siddique, Teepu; Sufit, Robert; Ajroud-Driss, Senda; Coleman, John M; Wolfe, Lisa F

2017-07-01

Amyotrophic lateral sclerosis (ALS) is a progressive neuromuscular disease resulting in respiratory failure and death. Use of noninvasive ventilation (NIV) improves survival. However, use of volume-assured pressure support (VAPS) has not been extensively studied in ALS. To explore the clinical usefulness of a detailed evaluation of device-recorded NIV data in the management of chronic respiratory failure in ALS, and to determine whether there are differences in efficacy between patients using VAPS or PS. We performed a retrospective chart review of 271 patients with ALS using either PS or VAPS, along with an evaluation of device-recorded data to explore differences in attainment of goal tidal volumes (Vt) and ratio of respiratory rate to tidal volume (f/Vt), in addition to triggering and cycling ability. Two hundred and fifteen patients were using PS, while 56 were using VAPS. There were no significant differences in demographic data, symptoms, pulmonary function, or patient compliance. Compared with VAPS, achieved Vt was significantly lower for PS while f/Vt was significantly higher. Percent spontaneous triggering was relatively preserved in both cohorts, whereas percent spontaneous cycling was considerably decreased in both. Furthermore, there was no association found between spontaneous triggering or cycling, and pulmonary function, indicating the presence of low spontaneous breath cycling or triggering ability is difficult to predict. Examination of device data for exhaled tidal volumes and f/Vt may be of use in evaluating efficacy of NIV in ALS. VAPS provides more reliable goal Vt than does PS, and is associated with decreased f/Vt. Spontaneous cycling is decreased in ALS despite preservation of triggering ability. Although a set backup rate may address decreased triggering, perhaps more importantly, setting a sufficient fixed inspiratory time would address the issue of decreased cycling.

The impact of arm position on the measurement of orthostatic blood pressure.

Science.gov (United States)

Guss, David A; Abdelnur, Diego; Hemingway, Thomas J

2008-05-01

Blood pressure is a standard vital sign in patients evaluated in an Emergency Department. The American Heart Association has recommended a preferred position of the arm and cuff when measuring blood pressure. There is no formal recommendation for arm position when measuring orthostatic blood pressure. The objective of this study was to assess the impact of different arm positions on the measurement of postural changes in blood pressure. This was a prospective, unblinded, convenience study involving Emergency Department patients with complaints unrelated to cardiovascular instability. Repeated blood pressure measurements were obtained using an automatic non-invasive device with each subject in a supine and standing position and with the arm parallel and perpendicular to the torso. Orthostatic hypotension was defined as a difference of >or= 20 mm Hg systolic or >or= 10 mm Hg diastolic when subtracting standing from supine measurements. There were four comparisons made: group W, arm perpendicular supine and standing; group X, arm parallel supine and standing; group Y, arm parallel supine and perpendicular standing; and group Z, arm perpendicular supine and parallel standing. There were 100 patients enrolled, 55 men, mean age 44 years. Four blood pressure measurements were obtained on each patient. The percentage of patients meeting orthostatic hypotension criteria in each group was: W systolic 6% (95% CI 1%, 11%), diastolic 4% (95% CI 0%, 8%), X systolic 8% (95% CI 3%, 13%), diastolic 9% (95% CI 3%, 13%), Y systolic 19% (95% CI 11%, 27%), diastolic 30% (95% CI 21%, 39%), Z systolic 2% (95% CI 0%, 5%), diastolic 2% (95% CI 0%, 5%). Comparison of Group Y vs. X, Z, and W was statistically significant (p postural changes in blood pressure. The combination of the arm parallel when supine and perpendicular when standing may significantly overestimate the orthostatic change. Arm position should be held constant in supine and standing positions when assessing for orthostatic

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

Duration of continuous positive airway pressure in premature infants

OpenAIRE

Bamat, Nicolas; Jensen, Erik A.; Kirpalani, Haresh

2016-01-01

Continuous positive airway pressure (CPAP) has been used for respiratory support in premature infants for more than 40 years and is now a cornerstone of modern neonatal care. Clinical research on CPAP has primarily focused on understanding which devices and pressure sources best implement this therapy. In contrast, less research has examined the optimal duration over which CPAP is administered. We review this aspect of CPAP therapy.

A Rotational Crofton Formula for Flagged Intrinsic Volumes of Sets of Positive Reach

DEFF Research Database (Denmark)

Auneau, Jeremy Michel

A rotational Crofton formula is derived relating the flagged intrinsic volumes of a compact set of positive reach with the flagged intrinsic volumes measured on sections passing through a fixed point. In particular cases, the flagged intrinsic volumes defined in the present paper are identical...

Low pulmonary artery flush perfusion pressure combined with high positive end-expiratory pressure reduces oedema formation in isolated porcine lungs

International Nuclear Information System (INIS)

Schumann, Stefan; Schließmann, Stephan J; Wagner, Giskard; Goebel, Ulrich; Priebe, Hans-Joachim; Guttmann, Josef; Kirschbaum, Andreas

2010-01-01

Flush perfusion of the pulmonary artery with organ protection solution is a standard procedure before lung explantation. However, rapid flush perfusion may cause pulmonary oedema which is deleterious in the lung transplantation setting. In this study we tested the hypotheses that high pulmonary perfusion pressure contributes to the development of pulmonary oedema and positive end-expiratory pressure (PEEP) counteracts oedema formation. We expected oedema formation to increase weight and decrease compliance of the lungs on the basis of a decrease in alveolar volume as fluid replaces alveolar air spaces. The pulmonary artery of 28 isolated porcine lungs was perfused with a low-potassium dextrane solution at low (mean 27 mmHg) or high (mean 40 mmHg) pulmonary artery pressure (PAP) during mechanical ventilation at low (4 cmH 2 O) or high (8 cmH 2 O) PEEP, respectively. Following perfusion and storage, relative increases in lung weight were smaller (p < 0.05) during perfusion at low PAP (62 ± 32% and 42 ± 26%, respectively) compared to perfusion at high PAP (133 ± 54% and 87 ± 30%, respectively). Compared to all other PAP–PEEP combinations, increases in lung weight were smallest (44 ± 9% and 27 ± 12%, respectively), nonlinear intratidal lung compliance was largest (46% and 17% respectively, both p < 0.05) and lung histology showed least infiltration of mononuclear cells in the alveolar septa, and least alveolar destruction during the combination of low perfusion pressure and high PEEP. The findings suggest that oedema formation during pulmonary artery flush perfusion in isolated and ventilated lungs can be reduced by choosing low perfusion pressure and high PEEP. PAP–PEEP titration to minimize pulmonary oedema should be based on lung mechanics and PAP monitoring

Duration of continuous positive airway pressure in premature infants

Science.gov (United States)

Bamat, Nicolas; Jensen, Erik A.; Kirpalani, Haresh

2016-01-01

SUMMARY Continuous positive airway pressure (CPAP) has been used for respiratory support in premature infants for more than 40 years and is now a cornerstone of modern neonatal care. Clinical research on CPAP has primarily focused on understanding which devices and pressure sources best implement this therapy. In contrast, less research has examined the optimal duration over which CPAP is administered. We review this aspect of CPAP therapy. PMID:26948885

Theoretical study of the partial molar volume change associated with the pressure-induced structural transition of ubiquitin.

Science.gov (United States)

Imai, Takashi; Ohyama, Shusaku; Kovalenko, Andriy; Hirata, Fumio

2007-09-01

The partial molar volume (PMV) change associated with the pressure-induced structural transition of ubiquitin is analyzed by the three-dimensional reference interaction site model (3D-RISM) theory of molecular solvation. The theory predicts that the PMV decreases upon the structural transition, which is consistent with the experimental observation. The volume decomposition analysis demonstrates that the PMV reduction is primarily caused by the decrease in the volume of structural voids in the protein, which is partially canceled by the volume expansion due to the hydration effects. It is found from further analysis that the PMV reduction is ascribed substantially to the penetration of water molecules into a specific part of the protein. Based on the thermodynamic relation, this result implies that the water penetration causes the pressure-induced structural transition. It supports the water penetration model of pressure denaturation of proteins proposed earlier.

Efeitos de diferentes volumes correntes e da pressão expiratória final positiva sobre a troca gasosa na fístula broncopleural experimental Effects of different tidal volumes and positive end expiratory pressure on gas exchange in experimental bronchopleural fistula

Directory of Open Access Journals (Sweden)

Maria Gabriela Cavicchia Toneloto

2008-09-01

melhora e o débito da fístula é reduzido quando comparado ao volume corrente de 10ml/Kg. Um baixo volume resulta em hipercapnia e grave dessaturação. Finalmente, em qualquer volume corrente, PEEP aumenta o débito da fístula e diminui a ventilação alveolar.OBJECTIVES: The present study was designed to identify the effect of positive end expiratory pressure (PEEP and the ideal pulmonary tidal volume to ventilate animals with a surgically produced bronchopleural fistula, aiming to reduce fistula output without affecting gas exchange. METHODS: Hemodynamic and respiratory assessment of gas exchange was obtained in five, healthy, young, mechanically ventilated Large White pigs under volume controlled ventilation with FiO2 of 0.4 and an inspiration:expiration ratio of 1:2, keeping respiratory rate at 22 cpm. A bronchopleural fistula was produced by resection of the lingula. Underwater seal drainage was installed and the thorax was hermetically closed. Gas exchange and fistula output were measured with the animals ventilated sequentially with tidal volumes of 4 ml/kg, 7 ml/kg and 10 ml/Kg alternating zero of positive end expiratory pressure (ZEEP and PEEP of 10 cmH2O, always in the same order. RESULTS: These findings are attributed to reduced alveolar ventilation and ventilation/perfusion abnormalities and were attenuated with larger tidal volumes. PEEP increases air leak, even with low volume (of 2.0 ± 2.8mL to 31 ± 20.7mL; p= 0.006 and decreases alveolar ventilation in all tidal volumes. Alveolar ventilation improved with larger tidal volumes, but increased fistula output (10 mL/kg - 25.8 ± 18.3mL to 80.2 ± 43.9mL; p=0.0010. Low tidal volumes result in hypercapnia (ZEEP - Toneloto MGC, Terzi RGG, Silva WA, Moraes AC, Moreira MM 83.7± 6.9 mmHg and with PEEP 10 - 93 ± 10.1mmHg and severely decreased arterial oxygen saturation, about of 84%. CONCLUSIONS: The tidal volume of 7 ml/Kg with ZEEP was considered the best tidal volume because, despite moderate hypercapnia

Regional respiratory inflation and deflation pressure-volume curves determined by electrical impedance tomography.

Science.gov (United States)

Frerichs, I; Dargaville, P A; Rimensberger, P C

2013-06-01

Measurement of regional lung volume changes during a quasi-static pressure-volume (PV) manoeuvre using electrical impedance tomography (EIT) could be used to assess regional respiratory system mechanics and to determine optimal ventilator settings in individual patients. Using this approach, we studied regional respiratory system mechanics in healthy and lung-injured animals, before and after surfactant administration during inflation and deflation PV manoeuvres. The comparison of the EIT-derived regional PV curves in ventral, middle and dorsal regions of the right and left lungs showed not only different amounts of hysteresis in these regions but also marked differences among different landmark pressures calculated on the inflation and deflation limbs of the curves. Regional pressures at maximum compliance as well as the lower and upper pressures of maximum compliance change differed between the inflation and deflation and increased from ventral to dorsal regions in all lung conditions. All these pressure values increased in the injured and decreased in the surfactant treated lungs. Examination of regional respiratory system mechanics using EIT enables the assessment of spatial and temporal heterogeneities in the ventilation distribution. Characteristic landmarks on the inflation and especially on the deflation limb of regional PV curves may become useful measures for guiding mechanical ventilation.

Sound pressure levels generated at risk volume steps of portable listening devices: types of smartphone and genres of music.

Science.gov (United States)

Kim, Gibbeum; Han, Woojae

2018-05-01

The present study estimated the sound pressure levels of various music genres at the volume steps that contemporary smartphones deliver, because these levels put the listener at potential risk for hearing loss. Using six different smartphones (Galaxy S6, Galaxy Note 3, iPhone 5S, iPhone 6, LG G2, and LG G3), the sound pressure levels for three genres of K-pop music (dance-pop, hip-hop, and pop-ballad) and a Billboard pop chart of assorted genres were measured through an earbud for the first risk volume that was at the risk sign proposed by the smartphones, as well as consecutive higher volumes using a sound level meter and artificial mastoid. The first risk volume step of the Galaxy S6 and the LG G2, among the six smartphones, had the significantly lowest (84.1 dBA) and highest output levels (92.4 dBA), respectively. As the volume step increased, so did the sound pressure levels. The iPhone 6 was loudest (113.1 dBA) at the maximum volume step. Of the music genres, dance-pop showed the highest output level (91.1 dBA) for all smartphones. Within the frequency range of 20~ 20,000 Hz, the sound pressure level peaked at 2000 Hz for all the smartphones. The results showed that the sound pressure levels of either the first volume step or the maximum volume step were not the same for the different smartphone models and genres of music, which means that the risk volume sign and its output levels should be unified across the devices for their users. In addition, the risk volume steps proposed by the latest smartphone models are high enough to cause noise-induced hearing loss if their users habitually listen to music at those levels.

Impact of continuous positive airway pressure on the pulmonary changes promoted by immersion in water

Directory of Open Access Journals (Sweden)

Danize Aparecida Rizzetti

Full Text Available ABSTRACT Objective: To determine whether different levels of CPAP improve the lung volumes and capacities of healthy subjects immersed in water. Methods: This was a randomized clinical trial, conducted between April and June of 2016, involving healthy female volunteers who were using oral contraceptives. Three 20-min immersion protocols were applied: control (no CPAP; CPAP5 (CPAP at 5 cmH2O; and CPAP10 (CPAP at 10 cmH2O. We evaluated HR, SpO2, FVC, FEV1, the FEV1/FVC ratio, peak expiratory flow rate (PEFR, and FEF25-75% at three time points: pre-immersion; 10 min after immersion; and 10 min after the end of each protocol. Results: We evaluated 13 healthy volunteers. The CPAP10 protocol reversed the restrictive pattern of lung function induced by immersion in water, maintaining pulmonary volumes and capacities for a longer period than did the CPAP5 protocol. Conclusions: When the hemodynamic change causing a persistent lung disorder, only the application of higher positive pressures is effective in maintaining long-term improvements in the pulmonary profile.

Impact of continuous positive airway pressure on the pulmonary changes promoted by immersion in water.

Science.gov (United States)

Rizzetti, Danize Aparecida; Quadros, Janayna Rodembuch Borba; Ribeiro, Bruna Esmerio; Callegaro, Letícia; Veppo, Aline Arebalo; Wiggers, Giulia Alessandra; Peçanha, Franck Maciel

2017-01-01

To determine whether different levels of CPAP improve the lung volumes and capacities of healthy subjects immersed in water. This was a randomized clinical trial, conducted between April and June of 2016, involving healthy female volunteers who were using oral contraceptives. Three 20-min immersion protocols were applied: control (no CPAP); CPAP5 (CPAP at 5 cmH2O); and CPAP10 (CPAP at 10 cmH2O). We evaluated HR, SpO2, FVC, FEV1, the FEV1/FVC ratio, peak expiratory flow rate (PEFR), and FEF25-75%) at three time points: pre-immersion; 10 min after immersion; and 10 min after the end of each protocol. We evaluated 13 healthy volunteers. The CPAP10 protocol reversed the restrictive pattern of lung function induced by immersion in water, maintaining pulmonary volumes and capacities for a longer period than did the CPAP5 protocol. When the hemodynamic change causing a persistent lung disorder, only the application of higher positive pressures is effective in maintaining long-term improvements in the pulmonary profile.

Can a central blood volume deficit be detected by systolic pressure variation during spontaneous breathing?

DEFF Research Database (Denmark)

Dahl, Michael; Hayes, Chris; Steen Rasmussen, Bodil

2016-01-01

BACKGROUND: Whether during spontaneous breathing arterial pressure variations (APV) can detect a volume deficit is not established. We hypothesized that amplification of intra-thoracic pressure oscillations by breathing through resistors would enhance APV to allow identification of a reduced card...

Optimum position for wells producing at constant wellbore pressure

Energy Technology Data Exchange (ETDEWEB)

Camacho-Velazquez, R.; Rodriguez de la Garza, F. [Univ. Nacional Autonoma de Mexico, Mexico City (Mexico); Galindo-Nava, A. [Inst. Mexicanos del Petroleo, Mexico City (Mexico)]|[Univ. Nacional de Mexico, Mexico City (Mexico); Prats, M.

1994-12-31

This paper deals with the determination of the optimum position of several wells, producing at constant different wellbore pressures from a two-dimensional closed-boundary reservoirs, to maximize the cumulative production or the total flow rate. To achieve this objective they authors use an improved version of the analytical solution recently proposed by Rodriguez and Cinco-Ley and an optimization algorithm based on a quasi-Newton procedure with line search. At each iteration the algorithm approximates the negative of the objective function by a cuadratic relation derived from a Taylor series. The improvement of rodriguez and Cinco`s solution is attained in four ways. First, an approximation is obtained, which works better at earlier times (before the boundary dominated period starts) than the previous solution. Second, the infinite sums that are present in the solution are expressed in a condensed form, which is relevant for reducing the computer time when the optimization algorithm is used. Third, the solution is modified to take into account the possibility of having wells starting to produce at different times. This point allows them to deal with the problem of getting the optimum position for an infill drilling program. Last, the solution is extended to include the possibility of changing the value of wellbore pressure or being able to stimulate any of the wells at any time. When the wells are producing at different wellbore pressures it is found that the optimum position is a function of time, otherwise the optimum position is fixed.

International pressure vessels and piping codes and standards. Volume 2: Current perspectives; PVP-Volume 313-2

International Nuclear Information System (INIS)

Rao, K.R.; Asada, Yasuhide; Adams, T.M.

1995-01-01

The topics in this volume include: (1) Recent or imminent changes to Section 3 design sections; (2) Select perspectives of ASME Codes -- Section 3; (3) Select perspectives of Boiler and Pressure Vessel Codes -- an international outlook; (4) Select perspectives of Boiler and Pressure Vessel Codes -- ASME Code Sections 3, 8 and 11; (5) Codes and Standards Perspectives for Analysis; (6) Selected design perspectives on flow-accelerated corrosion and pressure vessel design and qualification; (7) Select Codes and Standards perspectives for design and operability; (8) Codes and Standards perspectives for operability; (9) What's new in the ASME Boiler and Pressure Vessel Code?; (10) A look at ongoing activities of ASME Sections 2 and 3; (11) A look at current activities of ASME Section 11; (12) A look at current activities of ASME Codes and Standards; (13) Simplified design methodology and design allowable stresses -- 1 and 2; (14) Introduction to Power Boilers, Section 1 of the ASME Code -- Part 1 and 2. Separate abstracts were prepared for most of the individual papers

Effects of diluents on soot surface temperature and volume fraction in diluted ethylene diffusion flames at pressure

KAUST Repository

Kailasanathan, Ranjith Kumar Abhinavam

2014-05-20

Soot surface temperature and volume fraction are measured in ethylene/air coflowing laminar diffusion flames at high pressures, diluted with one of four diluents (argon, helium, nitrogen, and carbon dioxide) using a two-color technique. Both temperature and soot measurements presented are line-of-sight averages. The results aid in understanding the kinetic and thermodynamic behavior of the soot formation and oxidation chemistry with changes in diluents, ultimately leading to possible methods of reducing soot emission from practical combustion hardware. The diluted fuel and coflow exit velocities (top-hat profiles) were matched at all pressures to minimize shear effects. In addition to the velocity-matched flow rates, the mass fluxes were held constant for all pressures. Addition of a diluent has a pronounced effect on both the soot surface temperature and volume fraction, with the helium diluted flame yielding the maximum and carbon dioxide diluted flame yielding minimum soot surface temperature and volume fraction. At low pressures, peak soot volume fraction exists at the tip of the flame, and with an increase in pressure, the location shifts lower to the wings of the flame. Due to the very high diffusivity of helium, significantly higher temperature and volume fraction are measured and explained. Carbon dioxide has the most dramatic soot suppression effect. By comparing the soot yield with previously measured soot precursor concentrations in the same flame, it is clear that the lower soot yield is a result of enhanced oxidation rates rather than a reduction in precursor formation. Copyright © 2014 Taylor & Francis Group, LLC.

Transpulmonary pressures and lung mechanics with glossopharyngeal insufflation and exsufflation beyond normal lung volumes in competitive breath-hold divers.

Science.gov (United States)

Loring, Stephen H; O'Donnell, Carl R; Butler, James P; Lindholm, Peter; Jacobson, Francine; Ferrigno, Massimo

2007-03-01

Throughout life, most mammals breathe between maximal and minimal lung volumes determined by respiratory mechanics and muscle strength. In contrast, competitive breath-hold divers exceed these limits when they employ glossopharyngeal insufflation (GI) before a dive to increase lung gas volume (providing additional oxygen and intrapulmonary gas to prevent dangerous chest compression at depths recently greater than 100 m) and glossopharyngeal exsufflation (GE) during descent to draw air from compressed lungs into the pharynx for middle ear pressure equalization. To explore the mechanical effects of these maneuvers on the respiratory system, we measured lung volumes by helium dilution with spirometry and computed tomography and estimated transpulmonary pressures using an esophageal balloon after GI and GE in four competitive breath-hold divers. Maximal lung volume was increased after GI by 0.13-2.84 liters, resulting in volumes 1.5-7.9 SD above predicted values. The amount of gas in the lungs after GI increased by 0.59-4.16 liters, largely due to elevated intrapulmonary pressures of 52-109 cmH(2)O. The transpulmonary pressures increased after GI to values ranging from 43 to 80 cmH(2)O, 1.6-2.9 times the expected values at total lung capacity. After GE, lung volumes were reduced by 0.09-0.44 liters, and the corresponding transpulmonary pressures decreased to -15 to -31 cmH(2)O, suggesting closure of intrapulmonary airways. We conclude that the lungs of some healthy individuals are able to withstand repeated inflation to transpulmonary pressures far greater than those to which they would normally be exposed.

Development of a Blood Pressure Measurement Instrument with Active Cuff Pressure Control Schemes

Directory of Open Access Journals (Sweden)

Chung-Hsien Kuo

2017-01-01

Full Text Available This paper presents an oscillometric blood pressure (BP measurement approach based on the active control schemes of cuff pressure. Compared with conventional electronic BP instruments, the novelty of the proposed BP measurement approach is to utilize a variable volume chamber which actively and stably alters the cuff pressure during inflating or deflating cycles. The variable volume chamber is operated with a closed-loop pressure control scheme, and it is activated by controlling the piston position of a single-acting cylinder driven by a screw motor. Therefore, the variable volume chamber could significantly eliminate the air turbulence disturbance during the air injection stage when compared to an air pump mechanism. Furthermore, the proposed active BP measurement approach is capable of measuring BP characteristics, including systolic blood pressure (SBP and diastolic blood pressure (DBP, during the inflating cycle. Two modes of air injection measurement (AIM and accurate dual-way measurement (ADM were proposed. According to the healthy subject experiment results, AIM reduced 34.21% and ADM reduced 15.78% of the measurement time when compared to a commercial BP monitor. Furthermore, the ADM performed much consistently (i.e., less standard deviation in the measurements when compared to a commercial BP monitor.

A Simple Mercury-Free Laboratory Apparatus to Study the Relationship between Pressure, Volume, and Temperature in a Gas

Science.gov (United States)

McGregor, Donna; Sweeney, William V.; Mills, Pamela

2012-01-01

A simple and inexpensive mercury-free apparatus to measure the change in volume of a gas as a function of pressure at different temperatures is described. The apparatus is simpler than many found in the literature and can be used to study variations in pressure, volume, and temperature. (Contains 1 table and 7 figures.)

Does the position or contact pressure of the stethoscope make any difference to clinical blood pressure measurements: an observational study.

Science.gov (United States)

Pan, Fan; Zheng, Dingchang; He, Peiyu; Murray, Alan

2014-12-01

This study aimed to investigate the effect of stethoscope position and contact pressure on auscultatory blood pressure (BP) measurement. Thirty healthy subjects were studied. Two identical stethoscopes (one under the cuff, the other outside the cuff) were used to simultaneously and digitally record 2 channels of Korotkoff sounds during linear cuff pressure deflation. For each subject, 3 measurements with different contact pressures (0, 50, and 100 mm Hg) on the stethoscope outside the cuff were each recorded at 3 repeat sessions. The Korotkoff sounds were replayed twice on separate days to each of 2 experienced listeners to determine systolic and diastolic BPs (SBP and DBP). Variance analysis was performed to study the measurement repeatability and the effect of stethoscope position and contact pressure on BPs. There was no significant BP difference between the 3 repeat sessions, between the 2 determinations from each listener, between the 2 listeners and between the 3 stethoscope contact pressures (all P > 0.06). There was no significant SBP difference between the 2 stethoscope positions at the 2 lower stethoscope pressures (P = 0.23 and 0.45), but there was a small (0.4 mm Hg, clinically unimportant) significant difference (P = 0.005) at the highest stethoscope pressure. The key result was that, DBP from the stethoscope under the cuff was significantly lower than that from outside the cuff by 2.8 mm Hg (P stethoscope outside the cuff, tends to give a higher DBP than the true intra-arterial pressure, this study could suggest that the stethoscope position under the cuff, and closer to the arterial occlusion, might yield measurements closer to the actual invasive DBP.

Comparison of various state equations for approximation and extrapolation of experimental hydrogen molar volumes in wide temperature and pressure intervals

International Nuclear Information System (INIS)

Didyk, A.Yu.; Altynov, V.A.; Wisniewski, R.

2009-01-01

The numerical analysis of practically all existing formulae such as expansion series, Tait, logarithm, Van der Waals and virial equations for interpolation of experimental molar volumes versus high pressure was carried out. One can conclude that extrapolating dependences of molar volumes versus pressure and temperature can be valid. It was shown that virial equations can be used for fitting experimental data at relatively low pressures P<3 kbar too in distinction to other equations. Direct solving of a linear equation of the third order relatively to volume using extrapolated virial coefficients allows us to obtain good agreement between existing experimental data for high pressure and calculated values

Evaluation of Pressure Generated by Resistors From Different Positive Expiratory Pressure Devices.

Science.gov (United States)

Fagevik Olsén, Monika; Carlsson, Maria; Olsén, Erik; Westerdahl, Elisabeth

2015-10-01

Breathing exercises with positive expiratory pressure (PEP) are used to improve pulmonary function and airway clearance. Different PEP devices are available, but there have been no studies that describe the pressure generated by different resistors. The purpose of this study was to compare pressures generated from the proprietary resistor components of 4 commercial flow-dependent PEP valves with all other parameters kept constant. Resistors from 4 flow-regulated PEP devices (Pep/Rmt system, Wellspect HealthCare; Pipe P breathing exerciser, Koo Medical Equipment; Mini-PEP, Philips Respironics [including resistors by Rüsch]; and 15-mm endo-adapter, VBM Medizintechnik) were tested randomly by a blinded tester at constant flows of 10 and 18 L/min from an external gas system. All resistors were tested 3 times. Resistors with a similar diameter produced statistically significant different pressures at the same flow. The differences were smaller when the flow was 10 L/min compared with 18 L/min. The differences were also smaller when the diameter of the resistor was increased. The pressures produced by the 4 resistors of the same size were all significantly different when measuring 1.5- and 2.0-mm resistors at a flow of 10 L/min and 2.0-mm resistors at a flow of 18 L/min (P < .001). There were no significant differences between any of the resistors when testing sizes of 4.5 and 5.0 mm at either flow. The Mini-PEP and adapter resistors gave the highest pressures. Pressures generated by the different proprietary resistor components of 4 commercial PEP devices were not comparable, even though the diameter of the resistors is reported to be the same. The pressures generated were significantly different, particularly when using small-diameter resistors at a high flow. Therefore, the resistors may not be interchangeable. This is important information for clinicians, particularly when considering PEP for patients who do not tolerate higher pressures. Copyright © 2015 by

Pressure-volume-temperature gauging method experiment using liquid nitrogen under microgravity condition of parabolic flight

Energy Technology Data Exchange (ETDEWEB)

Seo, Man Su; Park, Hana; Yoo, Don Gyu; Jeong, Sang Kwon [Cryogenic Engineering Laboratory, Department of Mechanical Engineering, KAIST, Daejeon (Korea, Republic of); Jung, Young Suk [Launcher Systems Development Team, Korea Aerospace Research Institute, Daejeon (Korea, Republic of)

2014-06-15

Measuring an exact amount of remaining cryogenic liquid propellant under microgravity condition is one of the important issues of rocket vehicle. A Pressure-Volume-Temperature (PVT) gauging method is attractive due to its minimal additional hardware and simple gauging process. In this paper, PVT gauging method using liquid nitrogen is investigated under microgravity condition with parabolic flight. A 9.2 litre metal cryogenic liquid storage tank containing approximately 30% of liquid nitrogen is pressurized by ambient temperature helium gas. During microgravity condition, the inside of the liquid tank becomes near-isothermal condition within 1 K difference indicated by 6 silicon diode sensors vertically distributed in the middle of the liquid tank. Helium injection with higher mass flow rate after 10 seconds of the waiting time results in successful measurements of helium partial pressure in the tank. Average liquid volume measurement error is within 11% of the whole liquid tank volume and standard deviation of errors is 11.9. As a result, the applicability of PVT gauging method to liquid.

Pressure-volume-temperature gauging method experiment using liquid nitrogen under microgravity condition of parabolic flight

International Nuclear Information System (INIS)

Seo, Man Su; Park, Hana; Yoo, Don Gyu; Jeong, Sang Kwon; Jung, Young Suk

2014-01-01

Measuring an exact amount of remaining cryogenic liquid propellant under microgravity condition is one of the important issues of rocket vehicle. A Pressure-Volume-Temperature (PVT) gauging method is attractive due to its minimal additional hardware and simple gauging process. In this paper, PVT gauging method using liquid nitrogen is investigated under microgravity condition with parabolic flight. A 9.2 litre metal cryogenic liquid storage tank containing approximately 30% of liquid nitrogen is pressurized by ambient temperature helium gas. During microgravity condition, the inside of the liquid tank becomes near-isothermal condition within 1 K difference indicated by 6 silicon diode sensors vertically distributed in the middle of the liquid tank. Helium injection with higher mass flow rate after 10 seconds of the waiting time results in successful measurements of helium partial pressure in the tank. Average liquid volume measurement error is within 11% of the whole liquid tank volume and standard deviation of errors is 11.9. As a result, the applicability of PVT gauging method to liquid

Osmosis-induced water uptake by Eurobitum bituminized radioactive waste and pressure development in constant volume conditions

International Nuclear Information System (INIS)

Mariën, A.; Mokni, N.; Valcke, E.; Olivella, S.; Smets, S.; Li, X.

2013-01-01

Highlights: ► The water uptake by Eurobitum is studied to judge the safety of geological disposal. ► High pressures of up to 20 MPa are measured in constant volume water uptake tests. ► The morphology of leached Eurobitum samples is studied with μCT and ESEM. ► The observations are reproduced by an existing CHM formulation for Eurobitum. - Abstract: The chemo-hydro-mechanical (CHM) interaction between swelling Eurobitum radioactive bituminized waste (BW) and Boom Clay is investigated to assess the feasibility of geological disposal for the long-term management of this waste. These so-called compatibility studies include laboratory water uptake tests at Belgian Nuclear Research Center SCK-CEN, and the development of a coupled CHM formulation for Eurobitum by the International Center for Numerical Methods and Engineering (CIMNE, Polytechnical University of Cataluña, Spain). In the water uptake tests, the osmosis-induced swelling, pressure increase and NaNO 3 leaching of small cylindrical BW samples (diameter 38 mm, height 10 mm) is studied under constant total stress conditions and nearly constant volume conditions; the actual geological disposal conditions should be intermediate between these extremes. Two nearly constant volume tests were stopped after 1036 and 1555 days to characterize the morphology of the hydrated BW samples and to visualize the hydrated part with microfocus X-ray Computer Tomography (μCT) and Environmental Scanning Electron Microscopy (ESEM). In parallel, a coupled CHM formulation is developed that describes chemically and hydraulically coupled flow processes in porous materials with salt crystals, and that incorporates a porosity dependent membrane efficiency, permeability and diffusivity. When Eurobitum BW is hydrated in (nearly) constant volume conditions, the osmosis-induced water uptake results in an increasing pressure to values that can be (in theory) as high as 42.8 MPa, being the osmotic pressure of a saturated NaNO 3

Simulation of pore pressure accumulation under cyclic loading using Finite Volume Method

DEFF Research Database (Denmark)

Tang, Tian; Hededal, Ole

2014-01-01

This paper presents a finite volume implementation of a porous, nonlinear soil model capable of simulating pore pressure accumulation under cyclic loading. The mathematical formulations are based on modified Biot’s coupled theory by substituting the original elastic constitutive model...... with an advanced elastoplastic model suitable for describing monotonic as well as cyclic loading conditions. The finite volume method is applied to discretize these formulations. The resulting set of coupled nonlinear algebraic equations are then solved by a ’segregated’ solution procedure. An efficient return...

Pressure Dependence of Komatiite Liquid Viscosity and Implications for Magma Ocean Rheology

Science.gov (United States)

O'Dwyer Brown, L.; Lesher, C. E.; Terasaki, H. G.; Yamada, A.; Sakamaki, T.; Shibazaki, Y.; Ohtani, E.

2009-12-01

The viscosities of komatiite liquids at high pressures and temperatures were investigated using the in-situ falling sphere technique at BL04B1, SPring-8. Komatiites are naturally occurring magmas, rich in network modifying cations. Despite the refractory and fluid nature of komatiite, we successfully measured the viscosity of molten komatiites from Gorgona Island, Colombia (MgO = 17.8 wt.%; NBO/T = 1.5) between 11 and 13 GPa at 2000 C, and from Belingwe, Zimbabwe (MgO = 28.14 wt.%; NBO/T = 2.1) from 12 to 14 GPa at 2000 C. Under isothermal conditions, the viscosity of Gorgona Island komatiite melt increased with pressure, consistent with our previous measurements at lower pressures for this composition. We interpreted this positive pressure dependence as the result of reductions in interatomic space diminishing the free volume of the liquid when compressed. The viscosity of molten komatiite from Belingwe also increased up to 12 GPa, however between 12 and 14 GPa the viscosity is nearly constant. In previous studies of depolymerized silicate liquids, the pressure dependence of viscosity has been shown to reverse from positive to negative between 8 and 10 GPa with corresponding changes in activation volume [1] [2]. In contrast, the activation volume for Belingwe liquid decreases to near zero, but does not become negative above 11 GPa. Similarly, the activation volume for Gorgona Island komatiite remains positive throughout the pressure range investigated. Molecular dynamics simulations of simple MgO-SiO2 liquids with NBO/T > 2 also show a positive pressure dependence, reflecting the dominant control of free-volume reduction on the viscosity of depolymerized melts. However, the more rapid reduction in activation volume with pressure in komatiite liquids may be related to the presence of Al, Ti and other cations that interact and undergo coordination changes unavailable in simple silicate liquids. Along Hadean and post-Hadean mantle adiabats the net effect of

Effects of short-term pressure-controlled ventilation on gas exchange, airway pressures, and gas distribution in patients with acute lung injury/ARDS: comparison with volume-controlled ventilation.

Science.gov (United States)

Prella, Maura; Feihl, François; Domenighetti, Guido

2002-10-01

The potential clinical benefits of pressure-controlled ventilation (PCV) over volume-controlled ventilation (VCV) in patients with acute lung injury (ALI) or ARDS still remain debated. We compared PCV with VCV in patients with ALI/ARDS with respect to the following physiologic end points: (1) gas exchange and airway pressures, and (2) CT scan intrapulmonary gas distribution at end-expiration. Prospective, observational study. A multidisciplinary ICU in a nonuniversity, acute-care hospital. Ten patients with ALI or ARDS (9 men and 1 woman; age range, 17 to 80 years). Sequential ventilation in PCV and VCV with a constant inspiratory/expiratory ratio, tidal volume, respiratory rate, and total positive end-expiratory pressure; measurement of gas exchange and airway pressures; and achievement of CT sections at lung base, hilum, and apex for the quantitative analysis of lung densities and of aerated vs nonaerated zones. PaO(2), PaCO(2), and PaO(2)/fraction of inspired oxygen ratio levels did not differ between PCV and VCV. Peak airway pressure (Ppeak) was significantly lower in PCV compared with VCV (26 +/- 2 cm H(2)O vs 31 +/- 2 cm H(2)O; p mean +/- SEM). The surface areas of the nonaerated zones as well as the total areas at each section level were unchanged in PCV compared with VCV, except at the apex level, where there was a significantly greater nonaerated area in VCV (11 +/- 2 cm(2) vs 9 +/- 2 cm(2); p mean CT number of each lung (20 lungs from 10 patients) was similar in the two modes, as were the density values at the basal and apical levels; the hilum mean CT number was - 442 +/- 28 Hounsfield units (HU) in VCV and - 430 +/- 26 HU in PCV (p lower Ppeaks through the precise titration of the lung distending pressure, and might be applied to avoid regional overdistension by means of a more homogeneous gas distribution.

Effect of upper body position on arterial stiffness: influence of hydrostatic pressure and autonomic function.

Science.gov (United States)

Schroeder, Elizabeth C; Rosenberg, Alexander J; Hilgenkamp, Thessa I M; White, Daniel W; Baynard, Tracy; Fernhall, Bo

2017-12-01

To evaluate changes in arterial stiffness with positional change and whether the stiffness changes are due to hydrostatic pressure alone or if physiological changes in vasoconstriction of the conduit arteries play a role in the modulation of arterial stiffness. Thirty participants' (male = 15, 24 ± 4 years) upper bodies were positioned at 0, 45, and 72° angles. Pulse wave velocity (PWV), cardio-ankle vascular index, carotid beta-stiffness index, carotid blood pressure (cBP), and carotid diameters were measured at each position. A gravitational height correction was determined using the vertical fluid column distance (mmHg) between the heart and carotid artery. Carotid beta-stiffness was calibrated using three methods: nonheight corrected cBP of each position, height corrected cBP of each position, and height corrected cBP of the supine position (theoretical model). Low frequency systolic blood pressure variability (LFSAP) was analyzed as a marker of sympathetic activity. PWV and cardio-ankle vascular index increased with position (P hydrostatic pressure. Arterial stiffness indices based on Method 2 were not different from Method 3 (P = 0.65). LFSAP increased in more upright positions (P pressure did not (P > 0.05). Arterial stiffness increases with a more upright body position. Carotid beta-stiffness needs to be calibrated accounting for hydrostatic effects of gravity if measured in a seated position. It is unclear why PWV increased as this increase was independent of blood pressure. No difference between Methods 2 and 3 presumably indicates that the beta-stiffness increases are only pressure dependent, despite the increase in vascular sympathetic modulation.

High-pressure-assisted synthesis of high-volume ZnGeP2 polycrystalline

Science.gov (United States)

Huang, Changbao; Wu, Haixin; Xiao, Ruichun; Chen, Shijing; Ma, Jiaren

2018-06-01

The pnictide and chalcogenide semiconductors are promising materials for the applications in the field of photoelectric. High-purity and high-volume polycrystalline required in the real-world applications is hard to be synthesized due to the high vapor pressure of phosphorus and sulfur components at high temperature. A new high-pressure-resisted method was used to investigate the synthesis of the nonlinear-optical semiconductor ZnGeP2. The high-purity ZnGeP2 polycrystalline material of approximately 500 g was synthesized in one run, which enables the preparation of nominally stoichiometric material. Since increasing internal pressure resistance of quartz crucible and reducing the reaction space, the high-pressure-resisted method can be used to rapidly synthesize other pnictide and chalcogenide semiconductors and control the components ratio.

Non-invasive positive pressure ventilation for acute asthma in children

DEFF Research Database (Denmark)

Korang, Steven Kwasi; Feinberg, Joshua; Wetterslev, Jørn

2016-01-01

(age independently screened titles and abstracts. We retrieved all relevant full-text study reports, independently screened the full text, identified trials for inclusion and identified and recorded...... reasons for exclusion of ineligible trials. We resolved disagreements through discussion or, if required, consulted a third review author. We recorded the selection process in sufficient detail to complete a PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) flow diagram...... both studies as having high risk of bias; both trials assessed effects of bilateral positive airway pressure (BiPAP). Neither trial used continuous positive airway pressure (CPAP). Controls received standard care. Investigators reported no deaths and no serious adverse events (Grades of Recommendation...

Variable pattern contamination control under positive pressure

International Nuclear Information System (INIS)

Philippi, H.M.

1997-01-01

Airborne contamination control in nuclear and biological laboratories is traditionally achieved by directing the space ventilation air at subatmospheric pressures in one fixed flow pattern. However, biological and nuclear contamination flow control in the new Biological Research Facility, to be commissioned at the Chalk River Laboratories in 1996, will have the flexibility to institute a number of contamination control patterns, all achieved at positive (above atmospheric) pressures. This flexibility feature, made possible by means of a digitally controlled ventilation system, changes the facility ventilation system from being a relatively rigid building service operated by plant personnel into a flexible building service which can be operated by the facility research personnel. This paper focuses on and describes the application of these unique contamination control features in the design of the new Biological Research Facility. 3 refs., 7 figs

Variable pattern contamination control under positive pressure

Energy Technology Data Exchange (ETDEWEB)

Philippi, H.M. [Chalk River Labs., Ontario (Canada)

1997-08-01

Airborne contamination control in nuclear and biological laboratories is traditionally achieved by directing the space ventilation air at subatmospheric pressures in one fixed flow pattern. However, biological and nuclear contamination flow control in the new Biological Research Facility, to be commissioned at the Chalk River Laboratories in 1996, will have the flexibility to institute a number of contamination control patterns, all achieved at positive (above atmospheric) pressures. This flexibility feature, made possible by means of a digitally controlled ventilation system, changes the facility ventilation system from being a relatively rigid building service operated by plant personnel into a flexible building service which can be operated by the facility research personnel. This paper focuses on and describes the application of these unique contamination control features in the design of the new Biological Research Facility. 3 refs., 7 figs.

Determination of saturation pressure and enthalpy of vaporization of semi-volatile aerosols: the integrated volume mentod

Science.gov (United States)

This study presents the integrated volume method for estimating saturation pressure and enthalpy of vaporization of a whole aerosol distribution. We measure the change of total volume of an aerosol distribution between a reference state and several heated states, with the heating...

Effects of positive end-expiratory pressure on arthroscopic shoulder surgery under general anesthesia.

Science.gov (United States)

Ersoy, Ayşın; Çakırgöz, Mensure; Ervatan, Zekeriya; Kıran, Özlem; Türkmen, Aygen; Esenyel, Cem Zeki

2016-01-01

Our study is a prospective, randomized study on patients undergoing arthroscopic shoulder surgery in the beach-chair position to evaluate the effects of positive end-expiratory pressure (PEEP) on hemodynamic stability, providing a bloodless surgical field and surgical satisfaction. Fifty patients were divided into two groups. Group I (n=25) had zero end-expiratory pressure (ZEEP) administered under general anesthesia, and group II (n=25) had +5 PEEP administered. During surgery, intraarticular hemorrhage and surgical satisfaction were evaluated on a scale of 0-10. During surgery, at the 5th, 30th, 60th, and 90th minutes and at the end of surgery, heart rate, mean arterial pressure (MAP), and positive inspiratory pressure were recorded. At the end of the surgery, the amount of bleeding and duration of the operation were recorded. In group I, the duration of operation and amount of bleeding were found to be significantly greater than those in group II (pshoulder surgery in the beach-chair position reduces the amount of hemorrhage in the surgical field and thus increases surgical satisfaction without requiring the creation of controlled hypotension.

Insomnia complaints in lean patients with obstructive sleep apnea negatively affect positive airway pressure treatment adherence.

Science.gov (United States)

Eysteinsdottir, Bjorg; Gislason, Thorarinn; Pack, Allan I; Benediktsdottir, Bryndís; Arnardottir, Erna S; Kuna, Samuel T; Björnsdottir, Erla

2017-04-01

The objective of this study was to evaluate the determinants of long-term adherence to positive airway pressure treatment among patients with obstructive sleep apnea, with special emphasis on patients who stop positive airway pressure treatment within 1 year. This is a prospective long-term follow-up of subjects in the Icelandic Sleep Apnea Cohort who were diagnosed with obstructive sleep apnea between 2005 and 2009, and started on positive airway pressure treatment. In October 2014, positive airway pressure adherence was obtained by systematically evaluating available clinical files (n = 796; 644 males, 152 females) with moderate to severe obstructive sleep apnea (apnea-hypopnea index ≥15 events per h). The mean follow-up time was 6.7 ± 1.2 years. In total, 123 subjects (15.5%) returned their positive airway pressure device within the first year, 170 (21.4%) returned it later and 503 (63.2%) were still using positive airway pressure. The quitters within the first year had lower body mass index, milder obstructive sleep apnea, less sleepiness, and more often had symptoms of initial and late insomnia compared with long-term positive airway pressure users at baseline. Both initial and late insomnia were after adjustment still significantly associated with being an early quitter among subjects with body mass index insomnia are associated with early quitting on positive airway pressure among non-obese subjects. © 2016 European Sleep Research Society.

[A project to reduce the incidence of facial pressure ulcers caused by prolonged surgery with prone positioning].

Science.gov (United States)

Lee, Wen-Yi; Lin, Pao-Chen; Weng, Chia-Hsing; Lin, Yi-Lin; Tsai, Wen-Lin

2012-06-01

We observed in our institute a 13.6% incidence of prolonged surgery (>4 hours) induced facial pressure ulcers that required prone positioning. Causes identified included: (1) customized silicon face pillows used were not suited for every patient; (2) our institute lacked a standard operating procedure for prone positioning; (3) our institute lacked a postoperative evaluation and audit procedure for facial pressure ulcers. We designed a strategy to reduce post-prolonged surgery facial pressure ulcer incidence requiring prone positioning by 50% (i.e., from 13.6% to 6.8%). We implemented the following: (1) Created a new water pillow to relieve facial pressure; (2) Implemented continuing education pressure ulcer prevention and evaluation; (3) Established protocols on standard care for prone-position patients and proper facial pressure ulcer identification; (4) Established a face pressure ulcers accident reporting mechanism; and (5) Established an audit mechanism facial pressure ulcer cases. After implementing the resolution measures, 116 patients underwent prolonged surgery in a prone position (mean operating time: 298 mins). None suffered from facial pressure ulcers. The measures effectively reduced the incidence of facial pressure ulcers from 13.6% to 0.0%. The project used a water pillow to relieve facial pressure and educated staff to recognize and evaluate pressure ulcers. These measures were demonstrated effective in reducing the incidence of facial pressure ulcers caused by prolonged prone positioning.

Energy Performance and Pressure Fluctuation of a Multiphase Pump with Different Gas Volume Fractions

Directory of Open Access Journals (Sweden)

Jinsong Zhang

2018-05-01

Full Text Available Large petroleum resources in deep sea, and huge market demands for petroleum need advanced petroleum extraction technology. The multiphase pump, which can simultaneously transport oil and gas with considerable efficiency, has been a crucial technology in petroleum extraction. A numerical approach with mesh generation and a Navier-Stokes equation solution is employed to evaluate the effects of gas volume fraction on energy performance and pressure fluctuations of a multiphase pump. Good agreement of experimental and calculation results indicates that the numerical approach can accurately simulate the multiphase flow in pumps. The pressure rise of a pump decreases with the increasing of flow rate, and the pump efficiency decreases with the increasing of GVF (the ratio of the gas volume to the whole volume. Results show that the dominant frequencies of pressure fluctuation in the impeller and diffuser are eleven and three times those of the impeller rotational frequency, respectively. Due to the larger density of water and centrifugal forces, the water aggregates to the shroud and the gas gathers to the hub, which renders the distribution of GVF in the pump uneven. A vortex develops at the blade suction side, near the leading edge, induced by the leakage flow, and further affects the pressure fluctuation in the impeller. The obvious vortex in the diffuser indicates that the design of the divergence angle of the diffuser is not optimal, which induces flow separation due to large diffusion ratio. A uniform flow pattern in the impeller indicates good hydraulic performance of the pump.

Noninvasive Hemodynamic Measurements During Neurosurgical Procedures in Sitting Position.

Science.gov (United States)

Schramm, Patrick; Tzanova, Irene; Gööck, Tilman; Hagen, Frank; Schmidtmann, Irene; Engelhard, Kristin; Pestel, Gunther

2017-07-01

Neurosurgical procedures in sitting position need advanced cardiovascular monitoring. Transesophageal echocardiography (TEE) to measure cardiac output (CO)/cardiac index (CI) and stroke volume (SV), and invasive arterial blood pressure measurements for systolic (ABPsys), diastolic (ABPdiast) and mean arterial pressure (MAP) are established monitoring technologies for these kind of procedures. A noninvasive device for continuous monitoring of blood pressure and CO based on a modified Penaz technique (volume-clamp method) was introduced recently. In the present study the noninvasive blood pressure measurements were compared with invasive arterial blood pressure monitoring, and the noninvasive CO monitoring to TEE measurements. Measurements of blood pressure and CO were performed in 35 patients before/after giving a fluid bolus and a change from supine to sitting position, start of surgery, and repositioning from sitting to supine at the end of surgery. Data pairs from the noninvasive device (Nexfin HD) versus arterial line measurements (ABPsys, ABPdiast, MAP) and versus TEE (CO, CI, SV) were compared using Bland-Altman analysis and percentage error. All parameters compared (CO, CI, SV, ABPsys, ABPdiast, MAP) showed a large bias and wide limits of agreement. Percentage error was above 30% for all parameters except ABPsys. The noninvasive device based on a modified Penaz technique cannot replace arterial blood pressure monitoring or TEE in anesthetized patients undergoing neurosurgery in sitting position.

The position response of a large-volume segmented germanium detector

International Nuclear Information System (INIS)

Descovich, M.; Nolan, P.J.; Boston, A.J.; Dobson, J.; Gros, S.; Cresswell, J.R.; Simpson, J.; Lazarus, I.; Regan, P.H.; Valiente-Dobon, J.J.; Sellin, P.; Pearson, C.J.

2005-01-01

The position response of a large-volume segmented coaxial germanium detector is reported. The detector has 24-fold segmentation on its outer contact. The output from each contact was sampled with fast digital signal processing electronics in order to determine the position of the γ-ray interaction from the signal pulse shape. The interaction position was reconstructed in a polar coordinate system by combining the radial information, contained in the rise-time of the pulse leading edge, with the azimuthal information, obtained from the magnitude of the transient charge signals induced on the neighbouring segments. With this method, a position resolution of 3-7mm is achieved in both the radial and the azimuthal directions

The position response of a large-volume segmented germanium detector

Energy Technology Data Exchange (ETDEWEB)

Descovich, M. [Oliver Lodge Laboratory, Physics Department, University of Liverpool, Liverpool L69 7ZE (United Kingdom)]. E-mail: mdescovich@lbl.gov; Nolan, P.J. [Oliver Lodge Laboratory, Physics Department, University of Liverpool, Liverpool L69 7ZE (United Kingdom); Boston, A.J. [Oliver Lodge Laboratory, Physics Department, University of Liverpool, Liverpool L69 7ZE (United Kingdom); Dobson, J. [Oliver Lodge Laboratory, Physics Department, University of Liverpool, Liverpool L69 7ZE (United Kingdom); Gros, S. [Oliver Lodge Laboratory, Physics Department, University of Liverpool, Liverpool L69 7ZE (United Kingdom); Cresswell, J.R. [Oliver Lodge Laboratory, Physics Department, University of Liverpool, Liverpool L69 7ZE (United Kingdom); Simpson, J. [CCLRC Daresbury Laboratory, Daresbury, Warrington, Cheshire WA4 4AD (United Kingdom); Lazarus, I. [CCLRC Daresbury Laboratory, Daresbury, Warrington, Cheshire WA4 4AD (United Kingdom); Regan, P.H. [Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); Valiente-Dobon, J.J. [Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); Sellin, P. [Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); Pearson, C.J. [Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom)

2005-11-21

The position response of a large-volume segmented coaxial germanium detector is reported. The detector has 24-fold segmentation on its outer contact. The output from each contact was sampled with fast digital signal processing electronics in order to determine the position of the {gamma}-ray interaction from the signal pulse shape. The interaction position was reconstructed in a polar coordinate system by combining the radial information, contained in the rise-time of the pulse leading edge, with the azimuthal information, obtained from the magnitude of the transient charge signals induced on the neighbouring segments. With this method, a position resolution of 3-7mm is achieved in both the radial and the azimuthal directions.

Effects of continuous positive airway pressure on neurocognitive function in obstructive sleep apnea patients: The Apnea Positive Pressure Long-term Efficacy Study (APPLES).

Science.gov (United States)

Kushida, Clete A; Nichols, Deborah A; Holmes, Tyson H; Quan, Stuart F; Walsh, James K; Gottlieb, Daniel J; Simon, Richard D; Guilleminault, Christian; White, David P; Goodwin, James L; Schweitzer, Paula K; Leary, Eileen B; Hyde, Pamela R; Hirshkowitz, Max; Green, Sylvan; McEvoy, Linda K; Chan, Cynthia; Gevins, Alan; Kay, Gary G; Bloch, Daniel A; Crabtree, Tami; Dement, William C

2012-12-01

To determine the neurocognitive effects of continuous positive airway pressure (CPAP) therapy on patients with obstructive sleep apnea (OSA). The Apnea Positive Pressure Long-term Efficacy Study (APPLES) was a 6-month, randomized, double-blind, 2-arm, sham-controlled, multicenter trial conducted at 5 U.S. university, hospital, or private practices. Of 1,516 participants enrolled, 1,105 were randomized, and 1,098 participants diagnosed with OSA contributed to the analysis of the primary outcome measures. Active or sham CPAP MEASUREMENTS: THREE NEUROCOGNITIVE VARIABLES, EACH REPRESENTING A NEUROCOGNITIVE DOMAIN: Pathfinder Number Test-Total Time (attention and psychomotor function [A/P]), Buschke Selective Reminding Test-Sum Recall (learning and memory [L/M]), and Sustained Working Memory Test-Overall Mid-Day Score (executive and frontal-lobe function [E/F]) The primary neurocognitive analyses showed a difference between groups for only the E/F variable at the 2 month CPAP visit, but no difference at the 6 month CPAP visit or for the A/P or L/M variables at either the 2 or 6 month visits. When stratified by measures of OSA severity (AHI or oxygen saturation parameters), the primary E/F variable and one secondary E/F neurocognitive variable revealed transient differences between study arms for those with the most severe OSA. Participants in the active CPAP group had a significantly greater ability to remain awake whether measured subjectively by the Epworth Sleepiness Scale or objectively by the maintenance of wakefulness test. CPAP treatment improved both subjectively and objectively measured sleepiness, especially in individuals with severe OSA (AHI > 30). CPAP use resulted in mild, transient improvement in the most sensitive measures of executive and frontal-lobe function for those with severe disease, which suggests the existence of a complex OSA-neurocognitive relationship. Registered at clinicaltrials.gov. Identifier: NCT00051363. Kushida CA; Nichols DA; Holmes

Volume-pressure relationship (compliance) of interstitium in dog skin and muscle

International Nuclear Information System (INIS)

Wiig, H.; Reed, R.K.

1987-01-01

The relationship between changes in interstitial fluid volume (IFV) and pressure (IFP) during over- and dehydration was estimated in hindlimb skin and skeletal muscle of 17 dogs. IFV was measured as the extravascular distribution volume of 51 Cr-EDTA after nephrectomy and IFP with micropipettes, wick-in-needle technique (WIN), and perforated capsules. Control IFP (micropipettes) averaged -1.7 ± 0.5 and 0.0 ± 1.0 mmHg in skin and muscle, respectively, not different from corresponding WIN and capsule pressures in subcutis. Control IFV was 0.93 ± 0.34 and 0.42 ± 0.11 ml/g dry wt in skin and muscle, respectively. Peritoneal dialysis with 20% glucose reduced IFV by 27% in skin and by 44% in muscle, whereas micropipette IFP fell gradually by ∼ 4 mmHg in skin and muscle. Compliance during dehydration was 7.6 and 12.5% change in IFV per millimeter Hg fall in IFP (micropipettes) in skin and muscle, respectively, whereas compliance in subcutis based on perforated capsule pressure was 2.0% change in IFV per millimeter Hg. The maximal increase in IFP during overhydration was ∼2 mmHg in both skin and muscle. Skin and muscle compliance in dogs did not differ significantly from that of rats and cats. The authors conclude that the difference in compliance among previous studies mainly results from different methods for IFP measurement but is probably also influenced by the state of hydration before altering IFV

Bi-level positive airway pressure ventilation for treating heart failure with central sleep apnea that is unresponsive to continuous positive airway pressure.

Science.gov (United States)

Dohi, Tomotaka; Kasai, Takatoshi; Narui, Koji; Ishiwata, Sugao; Ohno, Minoru; Yamaguchi, Tetsu; Momomura, Shin-Ichi

2008-07-01

Cheyne-Stokes respiration with central sleep apnea (CSR-CSA) is associated with a poor prognosis in patients with heart failure (HF). However, some patients do not respond to continuous positive airway pressure (CPAP), so other therapeutic modalities should be considered, such as bi-level positive airway pressure (PAP), which also assists respiration and might be effective for such patients. The 20 patients with HF because of left ventricular systolic dysfunction were assessed: 8 had ischemic etiology, and all had severe CSA according to the apnea - hypopnea index (AHI) determined by polysomnography. All diagnosed patients underwent repeat polysomnography using CPAP. The AHI improved significantly in 11 (AHI or=15). Bi-level PAP titration significantly improved the AHI in the latter group. Those who were unresponsive to CPAP had significantly lower PaCO(2), higher plasma brain natriuretic peptide (BNP), longer mean duration of CSR and fewer obstructive episodes than CPAP responders. After 6 months of positive airway support with either CPAP (n=9) or bi-level PAP (n=7), BNP levels significantly decreased and left ventricular ejection fraction significantly increased. Bi-level PAP could be an effective alternative for patients with HF and pure CSR-CSA who are unresponsive to CPAP.

Noninvasive positive pressure ventilation enhances the effects of aerobic training on cardiopulmonary function.

Directory of Open Access Journals (Sweden)

Takashi Moriki

Full Text Available The purpose of this study was to determine the effect of aerobic training under noninvasive positive pressure ventilation (NPPV on maximal oxygen uptake ([Formula: see text].Ten healthy young male volunteers participated in the study. Before the training, stroke volume (SV and cardiac output (CO were measured in all subjects under 0, 4, 8, and 12 cmH2O NPPV at rest. Then, the subjects exercised on a cycle ergometer at 60% of pre-training [Formula: see text] for 30 min daily for 5 consecutive days with/without NPPV. The 5-day exercise protocol was repeated after a three-week washout period without/with NPPV. The primary endpoint was changes in [Formula: see text]. The secondary endpoints were changes in SV, CO, maximum heart rate (HRmax, maximum respiratory rate (RRmax, maximum expiratory minute volume (VEmax and the percent change in plasma volume (PV.NPPV at 12 cmH2O significantly reduced SV and CO at rest. [Formula: see text] significantly increased after 5 days training with and without NPPV, but the magnitude of increase in [Formula: see text] after training under 12 cmH2O NPPV was significantly higher than after training without NPPV. VEmax significantly increased after training under NPPV, but not after training without NPPV. HRmax and RRmax did not change during training irrespective of NPPV. The percent change in PV was similar between training with and without NPPV. The 5-day training program with NPPV resulted in greater improvement in [Formula: see text] than without NPPV.Aerobic training under NPPV has add-on effects on [Formula: see text] and exercise-related health benefits in healthy young men.

Backrest position in prevention of pressure ulcers and ventilator-associated pneumonia: conflicting recommendations.

Science.gov (United States)

Burk, Ruth Srednicki; Grap, Mary Jo

2012-01-01

Pressure ulcers and ventilator-associated pneumonia (VAP) are both common in acute and critical care settings and are considerable sources of morbidity, mortality, and health care costs. To prevent pressure ulcers, guidelines limit bed backrest elevation to less than 30 degrees, whereas recommendations to reduce VAP include use of backrest elevations of 30 degrees or more. Although a variety of risk factors beyond patient position have been identified for both pressure ulcers and VAP, this article will focus on summarizing the major evidence for each of these apparently conflicting positioning strategies and discuss implications for practice in managing mechanically ventilated patients with risk factors for both pressure ulcers and VAP. Copyright © 2012 Elsevier Inc. All rights reserved.

Effects of verapamil on left ventricular systolic and diastolic function in patients with hypertrophic cardiomyopathy: pressure-volume analysis with a nonimaging scintillation probe.

Science.gov (United States)

Bonow, R O; Ostrow, H G; Rosing, D R; Cannon, R O; Lipson, L C; Maron, B J; Kent, K M; Bacharach, S L; Green, M V

1983-11-01

To investigate the effects of verapamil on left ventricular systolic and diastolic function in patients with hypertrophic cardiomyopathy, we studied 14 patients at catheterization with a nonimaging scintillation probe before and after serial intravenous infusions of low-, medium-, and high-dose verapamil (total dose 0.17 to 0.72 mg/kg). Percent change in radionuclide stroke counts after verapamil correlated well with percent change in thermodilution stroke volume (r = .87), and changes in diastolic and systolic counts were used to assess relative changes in left ventricular volumes after verapamil. Verapamil produced dose-related increases in end-diastolic counts (19 +/- 9% increase; p less than .001), end-systolic counts (91 +/- 54% increase; p less than .001), and stroke counts (7 +/- 10% increase; p less than .02). This was associated with a decrease in ejection fraction (83 +/- 8% control, 73 +/- 10% verapamil; p less than .001) and, in the 10 patients with left ventricular outflow tract gradients, a reduction in gradient (62 +/- 27 mm Hg control, 32 +/- 35 mm Hg verapamil; p less than .01). The end-systolic pressure-volume relation was shifted downward and rightward in all patients, suggesting a negative inotropic effect. In 10 patients, left ventricular pressure-volume loops were constructed with simultaneous micromanometer pressure recordings and the radionuclide time-activity curve. In five patients, verapamil shifted the diastolic pressure-volume curve downward and rightward, demonstrating improved pressure-volume relations despite the negative inotropic effect, and also increased the peak rate of rapid diastolic filling. In the other five patients, the diastolic pressure-volume relation was unaltered by verapamil, and increased end-diastolic volumes occurred at higher end-diastolic pressures; in these patients, the peak rate of left ventricular diastolic filling was not changed by verapamil. The negative inotropic effects of intravenous verapamil are

First all-union symposium on shock pressures, October 24-26, 1973, Moscow. Volume 2

International Nuclear Information System (INIS)

Batsanov, S.S.

Twenty-two papers on the chemistry of impulsive pressures are contained in this volume. The papers deal primarily with shock wave propagation in various materials (particularly oxides) and explosive forming and sintering

An indigenous economic technique of positive pressure retrograde urethrography in female patients

Directory of Open Access Journals (Sweden)

H Singh

2001-01-01

Full Text Available Usually double balloon catheter is required forpositive pressure retrograde urethrography in females. We describe a technique of positive pressure retrograde urethrography using Foley catheter and rubber stopper, inexpensive and could be adopted in any hospital or radiological suite.

Effect of uncertainty in pore volumes on the uncertainty in amount adsorbed at high-pressures on activated carbon cloth

International Nuclear Information System (INIS)

Pendleton, Ph.; Badalyan, A.

2005-01-01

Activated carbon cloth (ACC) is a good adsorbent for high rate adsorption of volatile organic carbons [1] and as a storage media for methane [2]. It has been shown [2] that the capacity of ACC to adsorb methane, in the first instance, depends on its micropore volume. One way of increasing this storage capacity is to increase micropore volume [3]. Therefore, the uncertainty in the determination of ACC micropore volume becomes a very important factor, since it affects the uncertainty of amount adsorbed at high-pressures, which usually accompany storage of methane on ACC. Recently, we developed a method for the calculation of experimental uncertainty in micropore volume using low pressure nitrogen adsorption data at 77 K for FM1/250 ACC (ex. Calgon, USA). We tested several cubic equations of state (EOS) and multiple parameter (EOS) to determine the amount of high-pressure nitrogen adsorbed, and compared these data with amounts calculated via interpolated NIST density data. The amount adsorbed calculated from interpolated NIST density data exhibit the lowest propagated combined uncertainty. Values of relative combined standard uncertainty for FM1/250 calculated using a weighted, mean-least-squares method applied to the low-pressure nitrogen adsorption data (Fig. 1) gave 3.52% for the primary micropore volume and 1.63% for the total micropore volume. Our equipment allows the same sample to be exposed to nitrogen (and other gases) at pressures from 10 -4 Pa to 17-MPa in the temperature range from 176 to 252 K. The maximum uptake of nitrogen was 356-mmol/g at 201.92 K and 15.8-MPa (Fig. 2). The delivery capacity of ACC is determined by the amount of adsorbed gas recovered when the pressure is reduced from that for maximum adsorption to 0.1-MPa [2]. In this regard, the total micropore volume becomes an important parameter in determining the amount of gas delivered during desorption. In the present paper we will discuss the effect of uncertainty in micropore volume

[Preventing Facial Pressure Injuries in Patients Who Use Noninvasive Positive Pressure Ventilators: The Efficiency of Dressings].

Science.gov (United States)

Tai, Chia-Hua; Hsu, Mei-Yu

2016-10-01

Noninvasive positive pressure ventilation (NPPV) provides ventilation without tracheal intubation. Facial pressure injury is a recognized complication of this technique, making the prevention of facial pressure injuries an important issue for NPPV patients. The present study compared the effects of foam dressing and hydrocolloid dressing in preventing facial pressure injuries in NPPV patients. A randomized clinical trial was used to evaluate participants that were referred from the intensive care unit of a medical center in eastern Taiwan. Participants were randomized into two groups: the foam dressing group and the hydrocolloid dressing group. Statistics used in analysis were: analysis mean, standard deviation, chi-square, independent t-test, and the generalized estimating equation. Sixty participants were enrolled as participants. The incidence rate of facial pressure injury was 11.7% (7/60). No significant difference was found between the two groups in terms of duration of NPPV use, incidence of facial pressure injury, and occurrence time of facial pressure injury. However, the hydrocolloid dressing group had a higher usage amount than the foam dressing group (p < .05). Foam and hydrocolloid dressings are both helpful in preventing facial pressure injury when used in conjunction with regular skin assessments.

Heat release determination in a constant volume combustion chamber from the instantaneous cylinder pressure

International Nuclear Information System (INIS)

Lapuerta, Magín; Sanz-Argent, Josep; Raine, Robert

2014-01-01

A diagnostic method has been developed to interpret the results of basic combustion studies with diesel-like fuels performed in a constant volume reactor originally conceived for cetane number measurements. The main target of the method is to calculate the instantaneous heat release over time from the chamber pressure experimental signal. The method incorporates filtering of the raw data to eliminate the oscillations recorded as a consequence of the location of the pressure sensor. It considers homogeneity of the gaseous mixture (single zone model) and change in its composition due to the combustion process. A semi-empirical heat transfer model was also proposed and its coefficients were fitted from experimental results obtained in the constant volume chamber using diesel fuel. -- Highlights: • A diagnostic model for constant volume reactors has been developed and tested. • Updating the gas composition after combustion improves accuracy of the method. • Heat transfer coefficients are used for the fulfillment of boundary conditions. • The model provides a deeper insight than the apparent heat release analysis

Clinical application of a right ventricular pressure-volume loop determined by gated blood-pool imaging and simultaneously measured right ventricular pressure

International Nuclear Information System (INIS)

Yasue, Takao; Watanabe, Sachiro; Sugishita, Nobuyoshi; Tanaka, Tsutomu; Yokoyama, Hideo

1983-01-01

The data obtained by ECG-gated radionuclide angiography were collected simultaneously with right ventricular pressure and thermal cardiac output (CO) obtained by a Swan-Ganz catheter in Scintipac 1200 (Shimazu Co) in order to create a right ventricular pressure-volume (RV P-V) loop. Subjects consisted of 15 patients with old myocardial infarction (MI group), seven with angina pectoris (AP group), six with congestive cardiomyopathy (CCM group) and five with neurocirculatory asthenia (NCA group). Right ventricular end-diastolic volume (RVEDV) was calculated as RVEDV = CO/(EF x HR) (CO = cardiac output; HR = heart rate). Systolic work (W sub(S)), diastolic work (W sub(D)) and net work (W sub(N)) were calculated from a RV P-V loop by Simpson's method. The measurements were performed before and 5 min after sublingual administration of nitroglycerin (NG) (0.3 mg). The results were as follows: 1. RV P-V loops shifted towards the left lower part of the P-V plane after sublingual administration of nitroglycerin, indicating the reduction of pressure and volume of the right ventricle. 2. Right ventricular ejection fraction (RVEF) in the MI, AP and CCM groups showed smaller values than that of the NCA group. 3. Right ventricular end-diastolic volume index (RVEDVI) showed a converse relation with RVEF. 4. Cardiac index in all groups decreased after NG and a statistical significance was seen in the MI, AP and NCA groups (p<0.05). 5. RV W sub(S), RV W sub(D) and RV W sub(N) showed no difference among each groups in the control state, and significantly decreased after NG. We conclude that the present method using RV P-V loop might be useful as a noninvasive bedside monitoring and permits the evaluation of RV function in a clinical setting

Asymmetric Fuzzy Control of a Positive and Negative Pneumatic Pressure Servo System

Science.gov (United States)

Yang, Gang; Du, Jing-Min; Fu, Xiao-Yun; Li, Bao-Ren

2017-11-01

The pneumatic pressure control systems have been used in some fields. However, the researches on pneumatic pressure control mainly focus on constant pressure regulation. Poor dynamic characteristics and strong nonlinearity of such systems limit its application in the field of pressure tracking control. In order to meet the demand of generating dynamic pressure signal in the application of the hardware-in-the-loop simulation of aerospace engineering, a positive and negative pneumatic pressure servo system is provided to implement dynamic adjustment of sealed chamber pressure. A mathematical model is established with simulation and experiment being implemented afterwards to discuss the characteristics of the system, which shows serious asymmetry in the process of charging and discharging. Based on the analysis of the system dynamics, a fuzzy proportional integral derivative (PID) controller with asymmetric fuzzy compensator is proposed. Different from conventional adjusting mechanisms employing the error and change in error of the controlled variable as input parameters, the current chamber pressure and charging or discharging state are chosen as inputs of the compensator, which improves adaptability. To verify the effectiveness and performance of the proposed controller, the comparison experiments tracking sinusoidal and square wave commands are conducted. Experimental results show that the proposed controller can obtain better dynamic performance and relatively consistent control performance across the scope of work (2-140 kPa). The research proposes a fuzzy control method to overcome asymmetry and enhance adaptability for the positive and negative pneumatic pressure servo system.

Association between temporal mean arterial pressure and brachial noninvasive blood pressure during shoulder surgery in the beach chair position during general anesthesia.

Science.gov (United States)

Triplet, Jacob J; Lonetta, Christopher M; Everding, Nathan G; Moor, Molly A; Levy, Jonathan C

2015-01-01

Estimation of cerebral perfusion pressure during elective shoulder surgery in the beach chair position is regularly performed by noninvasive brachial blood pressure (NIBP) measurements. The relationship between brachial mean arterial pressure and estimated temporal mean arterial pressure (eTMAP) is not well established and may vary with patient positioning. Establishing a ratio between eTMAP and NIBP at varying positions may provide a more accurate estimation of cerebral perfusion using noninvasive measurements. This prospective study included 57 patients undergoing elective shoulder surgery in the beach chair position. All patients received an interscalene block and general anesthesia. After the induction of general anesthesia, values for eTMAP and NIBP were recorded at 0°, 30°, and 70° of incline. A statistically significant, strong, and direct correlation between NIBP and eTMAP was found at 0° (r = 0.909, P ≤ .001), 30° (r = 0.874, P Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

Substantial effect of acute hydration on blood pressure in patients with autonomic failure

DEFF Research Database (Denmark)

Mehlsen, J; Boesen, F

1987-01-01

fraction were measured in the supine position. Measurements were repeated after rapid infusion of 11 of isotonic saline. Acute hydration resulted in increased supine mean blood pressure levels (P less than 0.01) despite normal plasma volumes in all patients. The postural reductions in mean blood pressure......The effect of acute hydration on arterial blood pressure levels was investigated in ten patients with severe postural hypotension due to autonomic failure. Blood pressure and heart rate were determined in the supine and 60-degree head-up tilted position. Plasma volume and left ventricular ejection...... were reduced from 40 mmHg before to 20 mmHg after saline (median values, P less than 0.01). The results indicate that normal plasma volumes do not ensure optimal circulatory status in patients with autonomic failure. Acute hydration with isotonic saline may be used for immediate corrections of blood...

Stroke Volume estimation using aortic pressure measurements and aortic cross sectional area: Proof of concept.

Science.gov (United States)

Kamoi, S; Pretty, C G; Chiew, Y S; Pironet, A; Davidson, S; Desaive, T; Shaw, G M; Chase, J G

2015-08-01

Accurate Stroke Volume (SV) monitoring is essential for patient with cardiovascular dysfunction patients. However, direct SV measurements are not clinically feasible due to the highly invasive nature of measurement devices. Current devices for indirect monitoring of SV are shown to be inaccurate during sudden hemodynamic changes. This paper presents a novel SV estimation using readily available aortic pressure measurements and aortic cross sectional area, using data from a porcine experiment where medical interventions such as fluid replacement, dobutamine infusions, and recruitment maneuvers induced SV changes in a pig with circulatory shock. Measurement of left ventricular volume, proximal aortic pressure, and descending aortic pressure waveforms were made simultaneously during the experiment. From measured data, proximal aortic pressure was separated into reservoir and excess pressures. Beat-to-beat aortic characteristic impedance values were calculated using both aortic pressure measurements and an estimate of the aortic cross sectional area. SV was estimated using the calculated aortic characteristic impedance and excess component of the proximal aorta. The median difference between directly measured SV and estimated SV was -1.4ml with 95% limit of agreement +/- 6.6ml. This method demonstrates that SV can be accurately captured beat-to-beat during sudden changes in hemodynamic state. This novel SV estimation could enable improved cardiac and circulatory treatment in the critical care environment by titrating treatment to the effect on SV.

Partial molar volumes of organic solutes in water. XXIII. Cyclic ketones at T = (298 to 573) K and pressures up to 30 MPa

International Nuclear Information System (INIS)

Cibulka, Ivan; Simurka, Lukas; Hnedkovsky, Lubomir; Bolotov, Alexander

2011-01-01

Research highlights: → In this study we examine standard molar volumes of aqueous cyclic ketones. → State parameters of measurements were (298 to 573) K and pressures up to 30 MPa. → Differences in behavior of monoketones and cyclohexane-1,4-dione were observed. → Group contribution method was designed and examined. - Abstract: Density data for dilute aqueous solutions of four cyclic ketones (cyclopentanone, cyclohexanone, cycloheptanone, and cyclohexane-1,4-dione) are presented together with standard molar volumes (partial molar volumes at infinite dilution) calculated from the experimental data. The measurements were performed at temperatures from T = 298 K up to T = 573 K. Experimental pressures were close to the saturated vapor pressure of water, and (15 and 30) MPa. The data were obtained using a high-temperature high-pressure flow vibrating-tube densimeter. Experimental standard molar volumes were correlated as a function of temperature and pressure using an empirical polynomial function. Contributions of the molecular structural segments (methylene and carbonyl groups) to the standard molar volume were also evaluated and analyzed.

Nasal bi-level positive airway pressure (BiPAP) versus nasal continuous positive airway pressure (CPAP) in preterm infants ≤32 weeks: A retrospective cohort study.

Science.gov (United States)

Rong, Zhi-Hui; Li, Wen-Bin; Liu, Wei; Cai, Bao-Huan; Wang, Jing; Yang, Min; Li, Wei; Chang, Li-Wen

2016-05-01

To investigate whether Bi-level positive airway pressure (BiPAP), compared with nasal continuous positive airway pressure (CPAP), is a more effective therapeutic strategy in preterm infants ≤32 weeks. All inborn infants between 26(+1) and 32(+6) weeks' gestation, admitted to the neonatal intensive care unit (NICU ) of Tongji Medical Hospital between 1 January, 2010 and 31 December, 2011 (the 2010-2011 cohort or CPAP cohort) and between 1 January, 2012 and 31 December, 2013 (the 2012-2013 cohort or BiPAP cohort), were retrospectively identified. The primary outcome was intubation in infants CPAP were subsequently intubated (P CPAP, reduced the need for intubation within the first 72 h of age. © 2016 Paediatrics and Child Health Division (The Royal Australasian College of Physicians).

The effects of different lying positions on interface pressure, skin temperature, and tissue blood flow in nursing home residents.

Science.gov (United States)

Källman, Ulrika; Engström, Maria; Bergstrand, Sara; Ek, Anna-Christina; Fredrikson, Mats; Lindberg, Lars-Göran; Lindgren, Margareta

2015-03-01

Although repositioning is considered an important intervention to prevent pressure ulcers, tissue response during loading in different lying positions has not been adequately explored. To compare the effects of different lying positions on interface pressure, skin temperature, and tissue blood flow in nursing home residents. From May 2011 to August 2012, interface pressure, skin temperature, and blood flow at three tissue depths were measured for 1 hr over the sacrum in 30° supine tilt and 0° supine positions and over the trochanter major in 30° lateral and 90° lateral positions in 25 residents aged 65 years or older. Measurement of interface pressure was accomplished using a pneumatic pressure transmitter connected to a digital manometer, skin temperature using a temperature sensor, and blood flow using photoplethysmography and laser Doppler flowmetry. Interface pressure was significantly higher in the 0° supine and 90° lateral positions than in 30° supine tilt and 30° lateral positions. The mean skin temperature increased from baseline in all positions. Blood flow was significantly higher in the 30° supine tilt position compared to the other positions. A hyperemic response in the post pressure period was seen at almost all tissue depths and positions. The 30° supine tilt position generated less interface pressure and allowed greater tissue perfusion, suggesting that this position is the most beneficial. © The Author(s) 2014.

Positive end-expiratory pressure increases pulmonary clearance of inhaled 99mTc-DTPA in nonsmokers but not in healthy smokers

International Nuclear Information System (INIS)

Nolop, K.B.; Braude, S.; Royston, D.; Maxwell, D.L.; Hughes, J.M.B.

1987-01-01

Positive end-expiratory pressure (PEEP) is widely used in the treatment of severe pulmonary oedema, although its effects on the clearance of water and small solutes from alveolus to blood are not well characterized. We studied the effect of the application of 10 cmH 2 O of PEEP on the flux of inhaled 99 mTc-diethylene-triamine-penta-acetic acid (DTPA) from lung to blood in six healthy smoking and six nonsmoking subjects. The rate of flux was corrected for possible changes in pulmonary blood volume during PEEP by use of an intravenous injection of 99m Tc-DTPA. The baseline clearance rate (K,%.min -1 ) for nonsmokers was 1.48±0.12 (mean±SE) and increased to 2.40±0.29 during PEEP (p<0.05). In contrast, the mean clearance rate for smokers was 3.26±0.82 at baseline and 3.03±0.82 during PEEP (p=NS). The application of positive end-expiratory pressure appears to increase alveolar solute flux in nonsmokers but not in smokers, suggesting that the pathway for solute clearance in smokers is governed by different rate-limiting steps to those of nonsmokers

A switched energy saving position controller for variable-pressure electro-hydraulic servo systems.

Science.gov (United States)

Tivay, Ali; Zareinejad, Mohammad; Rezaei, S Mehdi; Baghestan, Keivan

2014-07-01

The electro-hydraulic servo system (EHSS) demonstrates a relatively low level of efficiency compared to other available actuation methods. The objective of this paper is to increase this efficiency by introducing a variable supply pressure into the system and controlling this pressure during the task of position tracking. For this purpose, an EHSS structure with controllable supply pressure is proposed and its dynamic model is derived from the basic laws of physics. A switching control structure is then proposed to control both the supply pressure and the cylinder position at the same time, in a way that reduces the overall energy consumption of the system. The stability of the proposed switching control system is guaranteed by proof, and its performance is verified by experimental testing. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

Amount of lifetime video gaming is positively associated with entorhinal, hippocampal and occipital volume.

Science.gov (United States)

Kühn, S; Gallinat, J

2014-07-01

Playing video games is a popular leisure activity among children and adults, and may therefore potentially influence brain structure. We have previously shown a positive association between probability of gray matter (GM) volume in the ventral striatum and frequent video gaming in adolescence. Here we set out to investigate structural correlates of video gaming in adulthood, as the effects observed in adolescents may reflect only a fraction of the potential neural long-term effects seen in adults. On magnetic resonance imaging (MRI) scans of 62 male adults, we computed voxel-based morphometry to explore the correlation of GM with the lifetime amount of video gaming (termed joystick years). We found a significant positive association between GM in bilateral parahippocamal region (entorhinal cortex) and left occipital cortex/inferior parietal lobe and joystick years (Pvideo game genres played, such as logic/puzzle games and platform games contributing positively, and action-based role-playing games contributing negatively. Furthermore, joystick years were positively correlated with hippocampus volume. The association of lifetime amount of video game playing with bilateral entorhinal cortex, hippocampal and occipital GM volume could reflect adaptive neural plasticity related to navigation and visual attention.

Increased nocturnal blood pressure in enuretic children with polyuria.

Science.gov (United States)

Kruse, Anne; Mahler, Birgitte; Rittig, Soren; Djurhuus, Jens Christian

2009-10-01

We investigated the association between nocturnal blood pressure and urine production in children with enuresis. A total of 39 consecutive children with a mean age of 9.8 years (range 6.2 to 14.9) with monosymptomatic nocturnal enuresis completed a bladder diary, including 2 weeks of basic documentation and 2 with desmopressin titration from 120 to 240 microg sublingually. Arterial blood pressure was measured every 30 minutes during 24 hours and during 4 additional nights using an ambulatory blood pressure monitor. Furthermore, 10 healthy children were recruited into the study who completed a bladder diary for 5 days while measuring arterial blood pressures with documentation of all intake and voided volumes. Patients with nocturnal polyuria had significantly higher nocturnal mean arterial pressure than patients without polyuria and controls (p polyuria than in children without polyuria. There was a significant positive correlation between average nocturnal mean arterial pressure and nocturnal urine volume in the whole study. The association between nocturnal blood pressure and urine volume, and the role of blood pressure should be investigated in a larger group of children with enuresis who have nocturnal polyuria.

Positive airway pressure adherence and mask interface in the setting of sinonasal symptoms.

Science.gov (United States)

Schell, Amy E; Soose, Ryan J

2017-10-01

Despite reports of lower positive pressure adherence rates with oronasal masks, patients with sinonasal problems are often prescribed this interface over a nasal interface. The aim of this study was to characterize the relationship between mask type and therapy adherence in the setting of sinonasal symptoms. Retrospective case series with chart review. We reviewed 328 patients who underwent positive pressure titration between January 2012 and May 2015. Follow-up adherence data were available for 218 patients (66.5%). Multivariate analysis examined whether patients with sinonasal symptoms have improved adherence with oronasal masks compared to nasal or nasal pillow interfaces. At a median follow-up of 95 days, positive pressure adherence in patients with sinonasal symptoms was highest with the nasal pillow interface. When compared with oronasal interfaces, the odds of adequate therapy adherence were >5 times greater with nasal pillow interfaces (odds ratio [OR] = 5.20, 95% confidence interval [CI] = 1.61-16.80, P = .006) and >3 times greater with nasal interfaces (OR = 3.67, 95% CI = 1.20-11.26, P = .02) in these symptomatic patients. The presence of nasal problems does not predict the need for an oronasal mask. Positive pressure adherence rates are higher with nasal and nasal pillow interfaces compared to oronasal masks, even in patients with sinonasal complaints. 4. Laryngoscope, 127:2418-2422, 2017. © 2016 The American Laryngological, Rhinological and Otological Society, Inc.

Relation Between Pressure and Volume Unloading During Ramp Testing in Patients Supported with a Continuous-Flow Left Ventricular Assist Device

DEFF Research Database (Denmark)

Jung, Mette H; Hassager, Christian; Balling, Louise

2015-01-01

Pulmonary capillary wedge pressure (PCWP) is the key to describing left ventricular (LV) unloading, however, the relation between pressure and the echocardiography-derived surrogate of LV volume (left ventricular end-diastolic diameter (LVEDD)) as a function of pump speed (RPM) in continuous......-flow left ventricular assist device (CF-LVAD) patients is unknown. In this study the pressure-volume relationship as a function of RPM during ramp testing was investigated by simultaneously measuring PCWP by Swan-Ganz catheter and LVEDD by echocardiography. The ramp protocol started at usual pump setting...

Boussignac continuous positive airway pressure for weaning with tracheostomy tubes

NARCIS (Netherlands)

Dieperink, Willem; Aarts, Leon P. H. J.; Rodgers, Michael G. G.; Delwig, Hans; Nijsten, Maarten W. N.

2008-01-01

Background: In patients who are weaned with a tracheostomy tube ( TT), continuous positive airway pressure ( CPAP) is frequently used. Dedicated CPAP systems or ventilators with bulky tubing are usually applied. However, CPAP can also be effective without a ventilator by the disposable Bous-signac

Pressure effect in the X-ray intrinsic position resolution in noble gases and mixtures

CERN Document Server

Azevedo, C.D.R.

2016-12-13

A study of the gas pressure effect in the position resolution of an interacting X- or gamma-ray photon in a gas medium is performed. The intrinsic position resolution for pure noble gases (Argon and Xenon) and their mixtures with CO2 and CH4 were calculated for several gas pressures (1-10bar) and for photon energies between 5.4 and 60.0 keV, being possible to establish a linear match between the intrinsic position resolution and the inverse of the gas pressure in that energy range. In order to evaluate the quality of the method here described, a comparison between the available experimental data and the calculated one in this work, is done and discussed. In the majority of the cases, a strong agreement is observed.

Association of an adult obesity, blood pressure adulthood socio-economic position.

Science.gov (United States)

Siadat, Zahra Dana; Abdoli, Aminreza; Shahsanaee, Armindokht

2012-03-01

The purpose of this study is to investigate an effect of childhood and adulthood socio-economic position on selected cardiovascular risk factors including obesity, blood pressure level and smoking behavior. This is a cross-sectional study performed on 479 individuals, randomly selected by random clustered sampling from men and women aged 30-50 years, living in Esfahan. Their demographic characteristics, education, occupation and smoking behavior were questioned. Their weight, height and blood pressure were also measured, and their BMI (Body Mass Index) was calculated. The data were analyzed by SPSS 19 software. In men, the odds ratio for ever smoking to never smoking at higher levels of education in comparison with the lower levels was 6.08 (2.65-14.11). For manual occupation to non-manual occupation, it was 3.55 (1.88-6.68). The odds ratio for obesity and overweight vs no overweight, for manual occupation to non-manual occupation was 3.12 (1.81-5.40) in men and for father's occupation it was 2.03 (1.10-3.74). In women, their education with the odds ratio of 2.11 (1.17-3.82) and father's occupation with the odds ratio of 6.63 (3.50-12.58) altered their chance of being obese or overweight. Also, in women, the mean systolic blood pressure was significantly lower at higher educational levels and in those whose fathers' occupation were manual but lower in manual workers. The current socio-economic position in individuals is associated with an obesity and smoking behavior, particularly in men. Childhood socio-economic position increases the chance of an obesity and higher blood pressure, particularly in women.

Interaction between peri-operative blood transfusion, tidal volume, airway pressure and postoperative ARDS: an individual patient data meta-analysis.

Science.gov (United States)

Serpa Neto, Ary; Juffermans, Nicole P; Hemmes, Sabrine N T; Barbas, Carmen S V; Beiderlinden, Martin; Biehl, Michelle; Fernandez-Bustamante, Ana; Futier, Emmanuel; Gajic, Ognjen; Jaber, Samir; Kozian, Alf; Licker, Marc; Lin, Wen-Qian; Memtsoudis, Stavros G; Miranda, Dinis Reis; Moine, Pierre; Paparella, Domenico; Ranieri, Marco; Scavonetto, Federica; Schilling, Thomas; Selmo, Gabriele; Severgnini, Paolo; Sprung, Juraj; Sundar, Sugantha; Talmor, Daniel; Treschan, Tanja; Unzueta, Carmen; Weingarten, Toby N; Wolthuis, Esther K; Wrigge, Hermann; de Abreu, Marcelo Gama; Pelosi, Paolo; Schultz, Marcus J

2018-01-01

Transfusion of blood products and mechanical ventilation with injurious settings are considered risk factors for postoperative lung injury in surgical Patients. A systematic review and individual patient data meta-analysis was done to determine the independent effects of peri-operative transfusion of blood products, intra-operative tidal volume and airway pressure in adult patients undergoing mechanical ventilation for general surgery, as well as their interactions on the occurrence of postoperative acute respiratory distress syndrome (ARDS). Observational studies and randomized trials were identified by a systematic search of MEDLINE, CINAHL, Web of Science, and CENTRAL and screened for inclusion into a meta-analysis. Individual patient data were obtained from the corresponding authors. Patients were stratified according to whether they received transfusion in the peri-operative period [red blood cell concentrates (RBC) and/or fresh frozen plasma (FFP)], tidal volume size [≤7 mL/kg predicted body weight (PBW), 7-10 and >10 mL/kg PBW] and airway pressure level used during surgery (≤15, 15-20 and >20 cmH 2 O). The primary outcome was development of postoperative ARDS. Seventeen investigations were included (3,659 patients). Postoperative ARDS occurred in 40 (7.2%) patients who received at least one blood product compared to 40 patients (2.5%) who did not [adjusted hazard ratio (HR), 2.32; 95% confidence interval (CI), 1.25-4.33; P=0.008]. Incidence of postoperative ARDS was highest in patients ventilated with tidal volumes of >10 mL/kg PBW and having airway pressures of >20 cmH 2 O receiving both RBC and FFP, and lowest in patients ventilated with tidal volume of ≤7 mL/kg PBW and having airway pressures of ≤15 cmH 2 O with no transfusion. There was a significant interaction between transfusion and airway pressure level (P=0.002) on the risk of postoperative ARDS. Peri-operative transfusion of blood products is associated with an increased risk of

Relationship of end-expiratory pressure, lung volume, and /sup 99m/Tc-DTPA clearance

International Nuclear Information System (INIS)

Cooper, J.A.; van der Zee, H.; Line, B.R.; Malik, A.B.

1987-01-01

We investigated the dose-response effect of positive end-expiratory pressure (PEEP) and increased lung volume on the pulmonary clearance rate of aerosolized technetium-99m-labeled diethylenetriaminepentaacetic acid (99mTc-DTPA). Clearance of lung radioactivity was expressed as percent decrease per minute. Base-line clearance was measured while anesthetized sheep (n = 20) were ventilated with 0 cmH 2 O end-expiratory pressure. Clearance was remeasured during ventilation at 2.5, 5, 10, 15, or 20 cmH 2 O PEEP. Further studies showed stepwise increases in functional residual capacity (FRC) (P less than 0.05) measured at 0, 2.5, 5, 10, 15, and 20 cmH 2 O PEEP. At 2.5 cmH 2 O PEEP, the clearance rate was not different from that at base line (P less than 0.05), although FRC was increased from base line. Clearance rate increased progressively with increasing PEEP at 5, 10, and 15 cmH 2 O (P less than 0.05). Between 15 and 20 cmH 2 O PEEP, clearance rate was again unchanged, despite an increase in FRC. The pulmonary clearance of aerosolized /sup 99m/Tc-DTPA shows a sigmoidal response to increasing FRC and PEEP, having both threshold and maximal effects. This relationship is most consistent with the hypothesis that alveolar epithelial permeability is increased by lung inflation

Fatigue and fracture mechanics in pressure vessels and piping. PVP-Volume 304

International Nuclear Information System (INIS)

Mehta, H.S.; Wilkowski, G.; Takezono, S.; Bloom, J.; Yoon, K.; Aoki, S.; Rahman, S.; Nakamura, T.; Brust, F.; Yoshimura, S.

1995-01-01

Fracture mechanics and fatigue evaluations are an important part of the structural integrity analyses to assure safe operation of pressure vessels and piping components during their service life. The paper presented in this volume illustrate the application of fatigue and fracture mechanics techniques to assess the structural integrity of a wide variety of Pressure Vessels and Piping components. The papers are organized in six sections: (1) fatigue and fracture--vessels; (2) fatigue and fracture--piping; (3) fatigue and fracture--material property evaluations; (4) constraint effects in fracture mechanics; (5) probabilistic fracture mechanics analyses; and (6) user's experience with failure assessment diagrams. Separate abstracts were prepared for most of the papers in this book

Multiple applications of the Boussignac continuous positive airway pressure system

NARCIS (Netherlands)

Dieperink, Willem

2008-01-01

Continuous positive airway pressure, (CPAP) is a form of treatment to support patients with dyspnea. For the application of CPAP a mechanical ventilator or complex CPAP apparatus is mostly used. The Boussignac CPAP (BCPAP) system developed by George Boussignac does not need such apparatus. The BCPAP

Thomson scattering in a low-pressure argon mercury positive column

NARCIS (Netherlands)

Bakker, L.P.; Kroesen, G.M.W.

2000-01-01

The electron density and the electron temperature in a low-pressure argon mercury positive column are determined using Thomson scattering. Special attention has been given to the stray light reduction in the Thomson scattering setup. The results are obtained in a discharge tube with a 26 mm diam, 5

Thomson scattering in a low-pressure neon mercury positive column

NARCIS (Netherlands)

Bakker, L.P.; Kroesen, G.M.W.

2001-01-01

The electron density and the electron temperature in a low-pressure neon mercury positive column are determined using Thomson scattering. Special attention has been given to the stray light reduction in the Thomson scattering setup. The results are obtained in a discharge tube with a 26 mm diam, 10

Early nasal continuous positive airway pressure in a cohort of the smallest infants in Denmark

DEFF Research Database (Denmark)

Hansen, Bo M; Esbjørn, Barbara Hoff; Greisen, G

2004-01-01

To evaluate neurodevelopmental outcome at age 5 y of age in a cohort of preterm children treated mainly with nasal continuous positive airway pressure (CPAP) in the neonatal period.......To evaluate neurodevelopmental outcome at age 5 y of age in a cohort of preterm children treated mainly with nasal continuous positive airway pressure (CPAP) in the neonatal period....

Intratidal recruitment/derecruitment persists at low and moderate positive end-expiratory pressure in paediatric patients.

Science.gov (United States)

Wirth, Steffen; Artner, Lisa; Broß, Tobias; Lozano-Zahonero, Sara; Spaeth, Johannes; Schumann, Stefan

2016-12-01

In paediatric patients positive end-expiratory pressure (PEEP) is traditionally set lower than in adults. We investigated whether moderately higher PEEP improves respiratory mechanics and regional ventilation. Therefore, 40 children were mechanically ventilated with PEEP 2 and 5cmH 2 O. Volume-dependent compliance profiles were analysed as a measure of intratidal recruitment/derecruitment. Regional ventilation was assessed using electrical impedance tomography. Mean compliance was 17.9±9.9mLcmH 2 O -1 (PEEP 2cmH 2 O), and 19.0±10.9mLcmH 2 O -1 (PEEP 5 cmH 2 O, pventilation. In conclusion, mechanically ventilated paediatric patients undergo intratidal recruitment/derecruitment which occurs more prominently in younger than in older children. A PEEP of 5cmH 2 O does not fully prevent intratidal recruitment/derecruitment but homogenizes regional ventilation in comparison to 2cmH 2 O. Copyright © 2016 Elsevier B.V. All rights reserved.

Influence of pressure and temperature on molar volume and retention properties of peptides in ultra-high pressure liquid chromatography.

Science.gov (United States)

Fekete, Szabolcs; Horváth, Krisztián; Guillarme, Davy

2013-10-11

In this study, pressure induced changes in retention were measured for model peptides possessing molecular weights between ∼1 and ∼4kDa. The goal of the present work was to evaluate if such changes were only attributed to the variation of molar volume and if they could be estimated prior to the experiments, using theoretical models. Restrictor tubing was employed to generate pressures up to 1000bar and experiments were conducted for mobile phase temperatures comprised between 30 and 80°C. As expected, the retention increases significantly with pressure, up to 200% for glucagon at around 1000bar compared to ∼100bar. The obtained data were fitted with a theoretical model and the determination coefficients were excellent (r(2)>0.9992) for the peptides at various temperatures. On the other hand, the pressure induced change in retention was found to be temperature dependent and was more pronounced at 30°C vs. 60 or 80°C. Finally, using the proposed model, it was possible to easily estimate the pressure induced increase in retention for any peptide and mobile phase temperature. This allows to easily estimating the expected change in retention, when increasing the column length under UHPLC conditions. Copyright © 2013 Elsevier B.V. All rights reserved.

Nasal continuous positive airway pressure: does bubbling improve gas exchange?

Science.gov (United States)

Morley, C J; Lau, R; De Paoli, A; Davis, P G

2005-07-01

In a randomised crossover trial, 26 babies, treated with Hudson prong continuous positive airway pressure (CPAP) from a bubbling bottle, received vigorous, high amplitude, or slow bubbling for 30 minutes. Pulse oximetry, transcutaneous carbon dioxide, and respiratory rate were recorded. The bubbling rates had no effect on carbon dioxide, oxygenation, or respiratory rate.

SCALE-4 analysis of pressurized water reactor critical configurations. Volume 1: Summary

International Nuclear Information System (INIS)

DeHart, M.D.

1995-03-01

The requirements of ANSI/ANS 8.1 specify that calculational methods for away-from-reactor criticality safety analyses be validated against experimental measurements. If credit is to be taken for the reduced reactivity of burned or spent fuel relative to its original fresh composition, it is necessary to benchmark computational methods used in determining such reactivity worth against spent fuel reactivity measurements. This report summarizes a portion of the ongoing effort to benchmark away-from-reactor criticality analysis methods using critical configurations from commercial pressurized water reactors (PWR). The analysis methodology utilized for all calculations in this report is based on the modules and data associated with the SCALE-4 code system. Each of the five volumes comprising this report provides an overview of the methodology applied. Subsequent volumes also describe in detail the approach taken in performing criticality calculations for these PWR configurations: Volume 2 describes criticality calculations for the Tennessee Valley Authority's Sequoyah Unit 2 reactor for Cycle 3; Volume 3 documents the analysis of Virginia Power's Surry Unit 1 reactor for the Cycle 2 core; Volume 4 documents the calculations performed based on GPU Nuclear Corporation's Three Mile Island Unit 1 Cycle 5 core; and, lastly, Volume 5 describes the analysis of Virginia Power's North Anna Unit 1 Cycle 5 core. Each of the reactor-specific volumes provides the details of calculations performed to determine the effective multiplication factor for each reactor core for one or more critical configurations using the SCALE-4 system; these results are summarized in this volume. Differences between the core designs and their possible impact on the criticality calculations are also discussed. Finally, results are presented for additional analyses performed to verify that solutions were sufficiently converged

Nap-titration : An effective alternative for continuous positive airway pressure titration

NARCIS (Netherlands)

Hoekema, A; Stegenga, B; Meinesz, AF; van der Hoeven, JH; Wijkstra, PJ

When treating Obstructive Steep Apnea-Hypopnea Syndrome (OSAHS) several alternatives for standard (manual) continuous positive airway pressure (CPAP) titration are feasible. A practical alternative is titration without polysomnography during an afternoon nap (Nap-titration). The aim of the present

Pressure effects on the structure, kinetic, and thermodynamic properties of heat-induced aggregation of protein studied by FT-IR spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Taniguchi, Y [Applied Chemistry Department, Ritsumeikan University, Kusatsu, Shiga 525-8577 (Japan); Okuno, A [Research Department 3, Central Research, Bridgestone Co. Kodaira, Tokyo 187-8531 (Japan); Kato, M, E-mail: taniguti@sk.ritsumei.ac.j [Pharmaceutical Sciences Department, Ritsumeikan University, Kusatsu, Shiga 525-8577 (Japan)

2010-03-01

Pressure can retrain the heat-induced aggregation and dissociate the heat-induced aggregates. We observed the aggregation-preventing pressure effect and the aggregates-dissociating pressure effect to characterize the heat-induced aggregation of equine serum albumin (ESA) by FT-IR spectroscopy. The results suggest the {alpha}-helical structure collapses at the beginning of heat-induced aggregation through the swollen structure, and then the rearrangement of structure to the intermolecular {beta}-sheet takes place through partially unfolded structure. We determined the activation volume for the heat-induced aggregation ({Delta}V'' = +93 ml/mol) and the partial molar volume difference between native state and heat-induced aggregates ({Delta}V=+32 ml/mol). This positive partial molar volume difference suggests that the heat-induced aggregates have larger internal voids than the native structure. Moreover, the positive volume change implies that the formation of the intermolecular {beta}-sheet is unfavorable under high pressure.

Effect of graft shape in lateral column lengthening on tarsal bone position and subtalar and talonavicular contact pressure in a cadaveric flatfoot model.

Science.gov (United States)

Campbell, Sean T; Reese, Keri A; Ross, Steven D; McGarry, Michelle H; Leba, Thu-Ba; Lee, Thay Q

2014-11-01

Lateral column lengthening (LCL) has been used for correction of flatfoot deformity. The purpose of this study was to determine the effect of LCL graft shape on tarsal bone position and talonavicular and subtalar joint pressure. A flatfoot model was created in 6 cadaveric specimens. Corrective LCL was performed using a rectangular graft or a trapezoidal graft with the broad surface oriented dorsally, laterally, or plantarly. Bony surface markers were digitized to calculate angular parameters used in the evaluation of flatfoot deformity. Contact pressure and area in the subtalar and talonavicular joints were also recorded. All measurements were carried out under multiple axial loads in the intact and flatfoot conditions, and following LCL with each graft shape. Flatfoot creation resulted in significant changes in arch collapse and forefoot abduction. LCL with a rectangular graft best corrected these parameters, while a laterally oriented trapezoidal graft provided some correction. Talonavicular contact pressure was unchanged after flatfoot creation, and was significantly less than intact after LCL. Subtalar contact pressure decreased in some conditions after flatfoot creation, and decreased further after LCL. LCL with a rectangular graft best restored tarsal bone orientation in a cadaveric flatfoot model. The decreases in talonavicular pressure likely represent redistribution of force from the medial to lateral foot. When performing LCL for flatfoot deformity, increased bone graft volume medially better restores tarsal bone position. One way of achieving this is through the use of a rectangular graft as opposed to a trapezoidal graft. © The Author(s) 2014.

Backrest position in prevention of pressure ulcers and ventilator-associated pneumonia: Conflicting recommendations

OpenAIRE

Burk, Ruth Srednicki; Jo Grap, Mary

2012-01-01

Pressure ulcers and ventilator-associated pneumonia (VAP) are both common in acute and critical care settings and are considerable sources of morbidity, mortality, and health care costs. To prevent pressure ulcers, guidelines limit bed backrest elevation to less than 30 degrees, whereas recommendations to reduce VAP include use of backrest elevations of 30 degrees or more. Although a variety of risk factors beyond patient position have been identified for both pressure ulcers and VAP, this ar...

Target Centroid Position Estimation of Phase-Path Volume Kalman Filtering

Directory of Open Access Journals (Sweden)

Fengjun Hu

2016-01-01

Full Text Available For the problem of easily losing track target when obstacles appear in intelligent robot target tracking, this paper proposes a target tracking algorithm integrating reduced dimension optimal Kalman filtering algorithm based on phase-path volume integral with Camshift algorithm. After analyzing the defects of Camshift algorithm, compare the performance with the SIFT algorithm and Mean Shift algorithm, and Kalman filtering algorithm is used for fusion optimization aiming at the defects. Then aiming at the increasing amount of calculation in integrated algorithm, reduce dimension with the phase-path volume integral instead of the Gaussian integral in Kalman algorithm and reduce the number of sampling points in the filtering process without influencing the operational precision of the original algorithm. Finally set the target centroid position from the Camshift algorithm iteration as the observation value of the improved Kalman filtering algorithm to fix predictive value; thus to make optimal estimation of target centroid position and keep the target tracking so that the robot can understand the environmental scene and react in time correctly according to the changes. The experiments show that the improved algorithm proposed in this paper shows good performance in target tracking with obstructions and reduces the computational complexity of the algorithm through the dimension reduction.

Diastolic chamber properties of the left ventricle assessed by global fitting of pressure-volume data: improving the gold standard of diastolic function.

Science.gov (United States)

Bermejo, Javier; Yotti, Raquel; Pérez del Villar, Candelas; del Álamo, Juan C; Rodríguez-Pérez, Daniel; Martínez-Legazpi, Pablo; Benito, Yolanda; Antoranz, J Carlos; Desco, M Mar; González-Mansilla, Ana; Barrio, Alicia; Elízaga, Jaime; Fernández-Avilés, Francisco

2013-08-15

In cardiovascular research, relaxation and stiffness are calculated from pressure-volume (PV) curves by separately fitting the data during the isovolumic and end-diastolic phases (end-diastolic PV relationship), respectively. This method is limited because it assumes uncoupled active and passive properties during these phases, it penalizes statistical power, and it cannot account for elastic restoring forces. We aimed to improve this analysis by implementing a method based on global optimization of all PV diastolic data. In 1,000 Monte Carlo experiments, the optimization algorithm recovered entered parameters of diastolic properties below and above the equilibrium volume (intraclass correlation coefficients = 0.99). Inotropic modulation experiments in 26 pigs modified passive pressure generated by restoring forces due to changes in the operative and/or equilibrium volumes. Volume overload and coronary microembolization caused incomplete relaxation at end diastole (active pressure > 0.5 mmHg), rendering the end-diastolic PV relationship method ill-posed. In 28 patients undergoing PV cardiac catheterization, the new algorithm reduced the confidence intervals of stiffness parameters by one-fifth. The Jacobian matrix allowed visualizing the contribution of each property to instantaneous diastolic pressure on a per-patient basis. The algorithm allowed estimating stiffness from single-beat PV data (derivative of left ventricular pressure with respect to volume at end-diastolic volume intraclass correlation coefficient = 0.65, error = 0.07 ± 0.24 mmHg/ml). Thus, in clinical and preclinical research, global optimization algorithms provide the most complete, accurate, and reproducible assessment of global left ventricular diastolic chamber properties from PV data. Using global optimization, we were able to fully uncouple relaxation and passive PV curves for the first time in the intact heart.

Pump out the volume--The effect of tracheal and subelytral pressure pulses on convective gas exchange in a dung beetle, Circellium bacchus (Fabricus).

Science.gov (United States)

Duncan, Frances D; Förster, Thomas D; Hetz, Stefan K

2010-05-01

Many flightless beetles like the large apterous dung beetle Circellium bacchus, possess a subelytral cavity (SEC) providing an extra air space below the elytra which connects to the tracheal system (TS) via metathoracic and abdominal spiracles. By measuring subelytral and intratracheal pressure as well as body movements and gas exchange simultaneously in a flow-through setup, we investigated the contribution of convection on Circellium respiratory gas exchange. No constriction phase was observed. TS and SEC pressures were always around atmospheric values. During interburst phase open abdominal spiracles and a leaky SEC led to small CO(2)-peaks on a continuous CO(2) baseline, driven by intermittent positive tracheal pressure peaks in anti-phase with small negative subelytral pressure peaks caused by dorso-ventral tergite action. Spiracle opening was accompanied by two types of body movements. Higher frequency telescoping body movements at the beginning of opening resulted in high amplitude SEC and TS pressure peaks. High frequency tergite movements caused subelytral pressure peaks and led to a saw tooth like CO(2) release pattern in a burst. We propose that during the burst open mesothoracic spiracles increase the compliance of the subelytral cavity allowing big volumes of tracheal air being pulled out by convection. Copyright 2009 Elsevier Ltd. All rights reserved.

High altitude pulmonary edema and exercise at 4,400 meters on Mount McKinley. Effect of expiratory positive airway pressure.

Science.gov (United States)

Schoene, R B; Roach, R C; Hackett, P H; Harrison, G; Mills, W J

1985-03-01

Breathing against positive expiratory pressure has been used to improve gas exchange in many forms of pulmonary edema, and forced expiration against resistance during exercise has been advocated for climbing at high altitude as a method to optimize performance. To evaluate the effect of expiratory positive airway pressure (EPAP) on climbers with high altitude pulmonary edema (HAPE) and on exercise at high altitude, we studied four climbers with HAPE at rest and 13 healthy climbers during exercise on a bicycle ergometer at 4400 m. We measured minute ventilation (VI, L/min), arterial oxygen saturation (SaO2 percent), end-tidal carbon dioxide (PACO2, mm Hg), respiratory rate (RR), and heart rate (HR) during the last minute of a five minute interval at rest in the climbers with HAPE, and at rest, 300, and 600 kpm/minute workloads on a bicycle ergometer in the healthy subjects. The HAPE subjects demonstrated an increased SaO2 percent, no change in HR or VI, and a decrease in RR on EPAP as compared to control. In normal subjects, SaO2 percent, VI, and heart rate were significantly higher on EPAP 10 cm H2O than 0 cm H2O control (p less than 0.01, 0.01, and 0.05, respectively). The RR and PaCO2 were not significantly different. In summary, EPAP improves gas exchange in HAPE subjects at rest. The EPAP in normal subjects at high altitude resulted in a higher SaO2 percent at the expense of a higher VI and higher HR. These results suggest that the work of breathing is higher and the stroke volume lower on EPAP. The positive pressure mask may be an effective temporizing measure for victims of HAPE who cannot immediately go to a lower altitude.

The effect of continuous positive airway pressure on blood pressure in patients with obstructive sleep apnea syndrome

Directory of Open Access Journals (Sweden)

Giorgiana Dediu

2017-12-01

Full Text Available Introduction. Obstructive sleep apnea syndrome (OSAS is a disease with increasing prevalence nowadays, being associated with multiple cardiovascular diseases, such as arterial hypertension. The objective of the study was to evaluate the effect of continuous positive airway pressure (CPAP on blood pressure values. Materials and methods. We performed a prospective interventional study on 52 patients with obstructive sleep apnea syndrome. The patients were divided into 2 groups: Group A (who received both pharmacological and CPAP treatment and Group B (who received only pharmacological treatment, and were followed up at 3 and 6 months. The statistical analysis was made with SPSS and Microsoft Excel. At the same time, using the surrogate marker –RDW, we tried to evaluate the persistence of systemic inflammation, knowing that OSAS is associated with inflammation. Results. The systolic blood pressure values decreased at 6 months in all OSAS patients who have used CPAP, including patients with normal values of blood pressure. At the same time, the lack of OSAS treatment led to increased values of blood pressure by approximately 10 mmHg. We noticed a link between RDW, age and blood pressure values, respectively the increase of RDW and age may result in an increase in blood pressure. Conclusions. The OSAS treatment can decrease the blood pressure values. A higher RDW may be considered a negative prognostic factor for these patients, reflecting the role of systemic inflammation in the appearance of cardiovascular disorders.

EFFECT OF BODY POSITIONS ON INTRA OCULAR PRESSURE

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Rajendra

2015-09-01

Full Text Available BACKGROUND: Intra Ocular Pressure (IOP can be altered by changing body position. Very few studies are available in the Indian subjects. AIM: To study the effect of changes in the body position from upright posture to supine to head down tilt of - 60 0 . MATERIALS AND M ETHODS: The study group consisted of 60 subjects, 35 boys and 25 girls in the age group of 18 to 24 years, with no ocular pathology were chosen. Independent measurements of the IOP of each eye were obtained. Keelar Pulsair air impulse tonometer was used in all the subjects for IOP measurement. IOP was measured in the department of Ophthalmology, Teaching Hospital between 10AM to 12 Noon. STATISTICAL ANALYSIS : were done using Student’s paired ‘t’ test. RESULTS: The change of IOP (Increased induced by the change of position between the means of IOP’s for the sitting and supine positions was 2.789±1.03 mm Hg of all subjects, 2.825±0.226 mm Hg in males and 2.739±0.089 mm Hg in females and between the supine and in clined - 60 ⁰ position was 4.971±0.914 mm Hg of all subjects, 4.703±0.816mm Hg in males and 5.346±1.098 mm Hg in females. CONCLUSION: It is apparent that, the IOP is significantly higher in the supine than in the sitting and in the inclined than in the supin e positions. The difference was statistically significant (P<0.001.

Prostate position variability and dose-volume histograms in radiotherapy for prostate cancer with full and empty bladder

International Nuclear Information System (INIS)

Pinkawa, Michael; Asadpour, Branka; Gagel, Bernd; Piroth, Marc D.; Holy, Richard; Eble, Michael J.

2006-01-01

Purpose: To evaluate prostate position variability and dose-volume histograms in prostate radiotherapy with full bladder (FB) and empty bladder (EB). Methods and Materials: Thirty patients underwent planning computed tomography scans in a supine position with FB and EB before and after 4 and 8 weeks of radiation therapy. The scans were matched by alignment of pelvic bones. Displacements of the prostate/seminal vesicle organ borders and center of mass were determined. Treatment plans (FB vs. EB) were compared. Results: Compared with the primary scan, FB volume varied more than EB volume (standard deviation, 106 cm 3 vs. 47 cm 3 ), but the prostate/seminal vesicle center of mass position variability was the same (>3 mm deviation in right-left, anterior-posterior, and superior-inferior directions in 0, 41%, and 33%, respectively, with FB vs. 0, 44%, and 33% with EB). The bladder volume treated with 90% of the prescription dose was significantly larger with EB (39% ± 14% vs. 22% ± 10%; p < 0.01). Bowel loops received ≥90% of prescription dose in 37% (3% with FB; p < 0.01). Conclusion: Despite the larger variability of bladder filling, prostate position stability was the same with FB compared with EB. An increased amount of bladder volume in the high-dose region and a higher dose to bowel loops result from treatment plans with EB

Pressure-induced amorphization of La1/3TaO3

International Nuclear Information System (INIS)

Noked, O.; Melchior, A.; Shuker, R.; Livneh, T.; Steininger, R.; Kennedy, B.J.; Sterer, E.

2013-01-01

La 1/3 TaO 3 , an A-site cation deficient perovskite, has been studied under pressure by synchrotron X-ray powder diffraction and Raman spectroscopy. It undergoes irreversible pressure induced amorphization at P=18.5 GPa. An almost linear unit cell volume decrease vs. pressure is observed from ambient pressure up to the phase transition. The Raman spectroscopy also shows amorphization at the same pressure, with positive shifts of all modes as a function of pressure. The pressure dependence of the E g and A 1g Raman modes arising from the octahedral oxygen network is discussed. - Graphical abstract: La 1/3 Tao 3 exhibits linear pressure–volume relation until irreversible pressure induced amorphization at 18.5 Gpa. - Highlights: • La 1/3 TaO 3 has been studied under pressure by synchrotron XRD and Raman spectroscopy. • La 1/3 TaO 3 undergoes irreversible pressure induced amorphization around 18.5 GPa. • The transition is manifested in both XRD and Raman measurements. • A linear P–V relation is observed from ambient pressure up to the phase transition

Densities and apparent molar volumes of aqueous LiI solutions at temperatures from (296 to 600) K and at pressures up to 30 MPa

International Nuclear Information System (INIS)

Abdulagatov, I.M.; Azizov, N.D.

2004-01-01

Densities of five aqueous LiI solutions (0.0906, 0.2832, 0.6621, 1.6046, and 3.0886) mol . kg -1 H 2 O were measured in the liquid phase with a constant-volume piezometer immersed in a precision liquid thermostat. Measurements were made along various isotherms between (296.95 and 600.25) K. The range of pressure was (0.1 to 30) MPa. The total uncertainty of density, pressure, temperature, and concentration measurements was estimated to be less than 0.06%, 0.05%, 15 mK, and 0.014%, respectively. To check and confirm the accuracy of the measurements, (p,V m ,T,x) data were taken for pure water at selected temperatures and pressures. Experimental and calculated (IAPWS formulation) densities for pure water show excellent agreement within their experimental uncertainties (average absolute deviation is 0.02%). Values of saturated densities were determined by extrapolating experimental p - ρ data to the vapour pressure at fixed temperature and composition using a linear interpolating equation. Apparent molar volumes were derived using measured values of density for solutions and pure water. The apparent molar volumes were extrapolated to zero concentration (m → 0) to yield partial molar volumes of electrolyte (LiI) at infinite dilution. The temperature, pressure, and concentration dependence of apparent and partial molar volumes was studied. The measured values of density, apparent and partial molar volume were compared with data reported in the literature by other authors. A polynomial type of equation of state for specific volume was obtained as a function of temperature, pressure, and composition by a least-squares method using the experimental data. The average absolute deviation (AAD) between measured and calculated values from this polynomial equation for density was 0.065%

Effect of body position on respiratory system volumes in anesthetized red-tailed hawks (Buteo jamaicensis) as measured via computed tomography.

Science.gov (United States)

Malka, Shachar; Hawkins, Michelle G; Jones, James H; Pascoe, Peter J; Kass, Philip H; Wisner, Erik R

2009-09-01

To determine the effects of body position on lung and air-sac volumes in anesthetized and spontaneously breathing red-tailed hawks (Buteo jamaicensis). 6 adult red-tailed hawks (sex unknown). A crossover study design was used for quantitative estimation of lung and air-sac volumes in anesthetized hawks in 3 body positions: dorsal, right lateral, and sternal recumbency. Lung volume, lung density, and air-sac volume were calculated from helical computed tomographic (CT) images by use of software designed for volumetric analysis of CT data. Effects of body position were compared by use of repeated-measures ANOVA and a paired Student t test. Results for all pairs of body positions were significantly different from each other. Mean +/- SD lung density was lowest when hawks were in sternal recumbency (-677 +/- 28 CT units), followed by right lateral (-647 +/- 23 CT units) and dorsal (-630 +/- 19 CT units) recumbency. Mean lung volume was largest in sternal recumbency (28.6 +/- 1.5 mL), followed by right lateral (27.6 +/- 1.7 mL) and dorsal (27.0 +/- 1.5 mL) recumbency. Mean partial air-sac volume was largest in sternal recumbency (27.0 +/- 19.3 mL), followed by right lateral (21.9 +/- 16.1 mL) and dorsal (19.3 +/- 16.9 mL) recumbency. In anesthetized red-tailed hawks, positioning in sternal recumbency resulted in the greatest lung and air-sac volumes and lowest lung density, compared with positioning in right lateral and dorsal recumbency. Additional studies are necessary to determine the physiologic effects of body position on the avian respiratory system.

A new methodological approach to assess cardiac work by pressure-volume and stress-length relations in patients with aortic valve stenosis and dilated cardiomyopathy.

Science.gov (United States)

Alter, P; Rupp, H; Rominger, M B; Klose, K J; Maisch, B

2008-01-01

In experimental animals, cardiac work is derived from pressure-volume area and analyzed further using stress-length relations. Lack of methods for determining accurately myocardial mass has until now prevented the use of stress-length relations in patients. We hypothesized, therefore, that not only pressure-volume loops but also stress-length diagrams can be derived from cardiac volume and cardiac mass as assessed by cardiac magnetic resonance imaging (CMR) and invasively measured pressure. Left ventricular (LV) volume and myocardial mass were assessed in seven patients with aortic valve stenosis (AS), eight with dilated cardiomyopathy (DCM), and eight controls using electrocardiogram (ECG)-gated CMR. LV pressure was measured invasively. Pressure-volume curves were calculated based on ECG triggering. Stroke work was assessed as area within the pressure-volume loop. LV wall stress was calculated using a thick-wall sphere model. Similarly, stress-length loops were calculated to quantify stress-length-based work. Taking the LV geometry into account, the normalization with regard to ventricular circumference resulted in "myocardial work." Patients with AS (valve area 0.73+/-0.18 cm(2)) exhibited an increased LV myocardial mass when compared with controls (Pwork of AS was unchanged when compared with controls (0.539+/-0.272 vs 0.621+/-0.138 Nm, not significant), whereas DCM exhibited a significant depression (0.367+/-0.157 Nm, Pwork was significantly reduced in both AS and DCM when compared with controls (129.8+/-69.6, 200.6+/-80.1, 332.2+/-89.6 Nm/m(2), Pmethodological approach of using CMR and invasive pressure measurement. Myocardial work was reduced in patients with DCM and noteworthy also in AS, while stroke work was reduced in DCM only. Most likely, deterioration of myocardial work is crucial for the prognosis. It is suggested to include these basic physiological procedures in the clinical assessment of the pump function of the heart.

Effect of Filters on the Noise Generated by Continuous Positive Airway Pressure Delivered via a Helmet

Directory of Open Access Journals (Sweden)

Ricardo Hernández-Molina

2017-01-01

Full Text Available Introduction: One of the problems that the delivery of continuous positive airway pressure (CPAP via a helmet poses is the generation of noise. The objective of our study was to assess the effect that the use of filter has on sound pressure levels generated by the delivery of positive airway pressure at different gas flow rates. Materials and Methods: Sound pressure levels generated by neonatal helmet CPAP delivery were measured at different gas flows (20, 30, and 40 l/min with and without a breathing filter. Noise intensity was measured by installing microphones in the inner ear of dummy heads wearing helmets. Results: The sound pressure level increased by 38% at a gas flow of 40 l/min, as compared to a gas flow of 20 l/min {74 dBA [interquartile range (IQR 2,2] vs 52 dBA (IQR 5,9, respectively}. Using the breathing filter as a diffuser has a variety of effects on sound pressure levels according to the gas flow rate. Conclusion: The intensity of the noise generated by helmet delivery of positive airway pressure depends on the type of helmet used, gas flow, and use or not of a diffuser filter. Breathing filters with gas flows over 30 l/min might not be recommended since they would not attenuate but will rather amplify sound pressure.

Mechanisms of blood pressure changes following renal irradiation of intact, adrenalectomized, and adrenal regenerating rats

International Nuclear Information System (INIS)

Rosenblum, M.

1977-01-01

This study was conducted to determine the differences in changes in systolic arterial blood pressure following renal x irradiation (1100 R) in adrenal-intact, adrenalectomized, and adrenal-regenerating rats and to elucidate the involvement or roles of the kidneys and of the adrenal glands in the blood pressure changes. The parameters studied included the following: systolic blood pressure; body weight; food and fluid consumption; urine output; plasma and urine electrolytes; sodium balance; plasma renin activity; plasma corticosterone; renal vascular volume; renal vascular permeability (using 125 I-polyvinylpyrrolidone extravasation rate as an indicator); renal blood flow (using 42 K extraction); kidney weight; hematocrit; and total vascular, plasma, and red cell volumes. Renal x irradiation of intact rats caused polydipsia, polyuria, and reduced urine concentrations of sodium and potassium without significantly affecting blood pressure during the period of study (80 days); plasma renin activity was significantly lowered and had a positive correlation with blood volume; an abnormal blood volume-plasma renin activity relationship is suggested. Adrenalectomy caused prolonged hypotension in saline-maintained rats even though their sodium balance was more positive than that in adrenal-intact or adrenal-regenerating rats with normal or elevated blood pressure. The blood pressure of renally irrradiated, adrenalectomized rats was greater than non-irradiated adrenalectomized rats, but with only borderline significance; it is concluded that the absence of the adrenal glands does not affect the degree or duration of the effects of renal irradiation on blood pressure

[Effects of recruitment maneuver in prone position on hemodynamics in patients with severe pulmonary infection].

Science.gov (United States)

Fan, Yuan-hua; Liu, Yuan-fei; Zhu, Hua-yong; Zhang, Min

2012-02-01

To evaluate effects of recruitment maneuver in prone position on hemodynamics in patients with severe pulmonary infection, based on the protective pulmonary ventilation strategy. Ninety-seven cases with severe pulmonary infection admitted to intensive care unit (ICU) of Ganzhou City People's Hospital undergoing mechanical ventilation were involved. Volume controlled ventilation mode with small tidal volume (8 ml/kg) and positive end-expiratory pressure (PEEP) of 6 cm H(2)O [1 cm H(2)O = 0.098 kPa] was conducted. Each patient underwent recruitment maneuver in supine position and then in prone position [PEEP 20 cm H(2)O+pressure control (PC) 20 cm H(2)O]. Heart rate (HR), mean arterial pressure (MAP), pulse oxygen saturation [SpO(2)] and blood gas analysis data were recorded before and after recruitment maneuver in either position. A double-lumen venous catheter was inserted into internal jugular vein or subclavian vein, and a pulse index contour cardiac output (PiCCO) catheter was introduced into femoral artery. Cardiac index (CI), stroke volume index (SVI), systemic vascular resistance index (SVRI), intra-thoracic blood volume index (ITBVI), extra vascular lung water index (EVLWI), global end-diastolic volume index (GEDVI), global ejection fraction (GEF), stroke volume variation (SVV) and central vein pressure (CVP) were monitored. (1) Compared with data before recruitment maneuver, there were no significant differences in HR and MAP after supine position and prone position recruitment maneuver, but significant differences in SpO(2) were found between before and after recruitment maneuver when patients' position was changed (supine position: 0.954 ± 0.032 vs. 0.917 ± 0.025, P recruitment maneuver (P recruitment maneuver, CI [L×min(-1)×m(-2)], SVI (ml/m(2)), GEDVI (ml/m(2)) and GEF were decreased significantly during recruitment maneuver (supine position: CI 3.2 ± 0.4 vs. 3.8 ± 0.6, SVI 32.4 ± 5.6 vs. 38.8 ± 6.5, GEDVI 689 ± 44 vs. 766 ± 32, GEF 0.267 ± 0

Effect of patient position and PEEP on hepatic, portal and central venous pressures during liver resection.

Science.gov (United States)

Sand, L; Rizell, M; Houltz, E; Karlsen, K; Wiklund, J; Odenstedt Hergès, H; Stenqvist, O; Lundin, S

2011-10-01

It has been suggested that blood loss during liver resection may be reduced if central venous pressure (CVP) is kept at a low level. This can be achieved by changing patient position but it is not known how position changes affect portal (PVP) and hepatic (HVP) venous pressures. The aim of the study was to assess if changes in body position result in clinically significant changes in these pressures. We studied 10 patients undergoing liver resection. Mean arterial pressure (MAP) and CVP were measured using fluid-filled catheters, PVP and HVP with tip manometers. Measurements were performed in the horizontal, head up and head down tilt position with two positive end expiratory pressure (PEEP) levels. A 10° head down tilt at PEEP 5 cm H(2) O significantly increased CVP (11 ± 3 to 15 ± 3 mmHg) and MAP (72 ± 8 to 76 ± 8 mmHg) while head up tilt at PEEP 5 cm H(2) O decreased CVP (11 ± 3 to 6 ± 4 mmHg) and MAP (72 ± 8 to 63 ± 7 mmHg) with minimal changes in transhepatic venous pressures. Increasing PEEP from 5 to 10 resulted in small increases, around 1 mmHg in CVP, PVP and HVP. There was no significant correlation between changes in CVP vs. PVP and HVP during head up tilt and only a weak correlation between CVP and HVP by head down tilt. Changes of body position resulted in marked changes in CVP but not in HVPs. Head down or head up tilt to reduce venous pressures in the liver may therefore not be effective measures to reduce blood loss during liver surgery. 2011 The Authors Acta Anaesthesiologica Scandinavica, 2011 The Acta Anaesthesiologica Scandinavica Foundation.

Partial molar volumes of organic solutes in water. XXIV. Selected alkane-α,ω-diols at temperatures T = 298 K to 573 K and pressures up to 30 MPa

International Nuclear Information System (INIS)

Cibulka, Ivan; Hnědkovský, Lubomír

2013-01-01

Highlights: • Standard molar volumes of three alkane-α,ω-diols (C 5 , C 8 , C 9 ) in water are presented. • Data were obtained in the range T from (298 to 573) K and p up to 30 MPa. • Dependences on carbon atom number, temperature, and pressure are analysed. -- Abstract: Density data for dilute aqueous solutions of three alkane-α,ω-diols (pentane-1,5-diol, octane-1,8-diol, nonane-1,9-diol) are presented together with standard molar volumes (partial molar volumes at infinite dilution) calculated from the experimental data. The measurements were performed at temperatures from T = 298 K up to T = 573 K. Experimental pressures were slightly above the saturation vapour pressure of water, and (15 and 30) MPa. The data were obtained using a high-temperature high-pressure flow vibrating-tube densimeter. Measured standard molar volumes were combined with data previously published for other members of the homologous series and discussed. Experimental standard molar volumes were correlated as a function of temperature and pressure using an empirical polynomial function. Dependences of standard molar volumes on temperature and pressure were analysed. Contributions of the methylene group to the standard molar volume were also evaluated and discussed

Arterial compliance in patients with cirrhosis: stroke volume-pulse pressure ratio as simplified index

DEFF Research Database (Denmark)

Fuglsang, S; Bendtsen, F; Christensen, E

2001-01-01

Arterial function may be altered in patients with cirrhosis. We determined compliance of the arterial tree (C(1)) in relation to systemic and splanchnic hemodynamic derangement and clinical variables. C(1) and the stroke volume-pulse pressure index (SV/PP) were significantly higher (+62% and +40%...... predictors of SV/PP (P abnormalities in the arterial compliance of these patients....

Impact of Polysomnographic Parameters on Continuous Positive Airway Pressure in Patient with Obstructive Sleep Apnea in 2012

Directory of Open Access Journals (Sweden)

Abolfazl Mozafari

2014-06-01

Full Text Available Background & objectives : O bstructive sleep apnea is a preventable and prevalent major health hazard with serious health consequences including excessive daytime sleepiness, cognitive disturbances, depression, cardiovascular diseases and hypertension. Obstructive sleep apnea is a disorder affecting 2 to 4% of the adult population. The continuous positive airway pressur e (CPAP i s the most efficacious therapy and is often the first option for these patients. The pressure titration during laboratory polysomnography is required for treatment by CPAP.   Methods: The patients with obstructive sleep apnea requiring continuous positive airway pressure treatment were selected . CPAP titration was done according to American Academy of Sleep Medicine protocol. Comparison among continuous positive airway pressure with polysomnographic parameters was performed and analyzed with Pearson correlation coefficient. For analysis of qualitative parameters, we used chi-square and then checked with SPSS version 18 software.   Results: From 125 patients with obstructive sleep apnea, there were 112 cases with inclusion criteria. Mean age of participants was 55.07 ± 12, male frequency was 59.2%, apnea hypopnea index was 43.62 and mean continuous positive airway pressure was 12.50 . There was significant relationship among the pressure of continuous positive airway pressure with apnea hypopnea index (P=0.028, arousal index (P=0.011, body mass index (P=0.041 and O2 desaturation index (P=0.022, although age was not significantly related.   Conclusion: In accordance to this data, we found out a prediction equation for optimal CPAP in our patients

Randomized controlled trial comparing nasal intermittent positive pressure ventilation and nasal continuous positive airway pressure in premature infants after tracheal extubation

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Daniela Franco Rizzo Komatsu

Full Text Available Summary Objective: To analyze the frequency of extubation failure in premature infants using conventional mechanical ventilation (MV after extubation in groups subjected to nasal intermittent positive pressure ventilation (nIPPV and continuous positive airway pressure (nCPAP. Method: Seventy-two premature infants with respiratory failure were studied, with a gestational age (GA ≤ 36 weeks and birth weight (BW > 750 g, who required tracheal intubation and mechanical ventilation. The study was controlled and randomized in order to ensure that the members of the groups used in the research were chosen at random. Randomization was performed at the time of extubation using sealed envelopes. Extubation failure was defined as the need for re-intubation and mechanical ventilation during the first 72 hours after extubation. Results: Among the 36 premature infants randomized to nIPPV, six (16.6% presented extubation failure in comparison to 11 (30.5% of the 36 premature infants randomized to nCPAP. There was no statistical difference between the two study groups regarding BW, GA, classification of the premature infant, and MV time. The main cause of extubation failure was the occurrence of apnea. Gastrointestinal and neurological complications did not occur in the premature infants participating in the study. Conclusion: We found that, despite the extubation failure of the group of premature infants submitted to nIPPV being numerically smaller than in premature infants submitted to nCPAP, there was no statistically significant difference between the two modes of ventilatory support after extubation.

On the Existence of Shock Instabilities at Hugoniot Pressures Beyond the Minimum Volume

Science.gov (United States)

Heuzé, Olivier; Pain, Jean-Christophe; Salin, Gwenael

2009-12-01

Flow instabilities are among the main issues of ICF studies. Heterogeneities and defects of the material or the geometry are generally considered among the sources of instabilities which are strongly amplified in spherical geometries. According to the theory of D'yakov, some ranges of the Equation of State (EOS) also generate or amplify instabilities in shock waves, which can be considered among the origin of Richtmyer-Meshkov instabilities. It is well known that, on the Hugoniot curve of most materials, the volume decreases versus pressure down to a minimum and then increases with ionization towards an asymptotic value. Recent results in this range of pressure allow us to investigate now the stability conditions. The first question to raise is the possibility of existence of such instabilities. We focus here on the properties of several elements (aluminium, iron, copper) in this range of pressure to try to give a first answer to this question.

Pars-plana fluid aspiration for positive vitreous cavity pressure in anterior segment surgeries

Directory of Open Access Journals (Sweden)

Thomas Kuriakose

2018-01-01

Full Text Available Positive vitreous pressure due to misdirection of aqueous or choroidal effusion leads to shallowing of the anterior chamber (AC before or during anterior segment surgeries. This shallow AC if not addressed makes surgery difficult and increases the risk of surgical complications. Methods to prevent and manage this condition described in literature are not without problems. We describe a minimally invasive technique of passing a 30G needle through the pars-plana to aspirate misdirected fluid from vitreous cavity either as a prophylaxis just before surgery or during it, thereby decreasing positive vitreous pressure. This technique, used in 12 eyes, seems to be effective in patients with angle-closure glaucoma, malignant glaucoma, and per-operative sudden increase in vitreous pressure during surgery. Small-incision surgeries are ideally suited for this procedure. This minimally invasive technique is simple to perform and complications are unlikely to be more than what is seen with intravitreal injections.

Clinical predictors of central sleep apnea evoked by positive airway pressure titration.

Science.gov (United States)

Moro, Marilyn; Gannon, Karen; Lovell, Kathy; Merlino, Margaret; Mojica, James; Bianchi, Matt T

2016-01-01

Treatment-emergent central sleep apnea (TECSA), also called complex apnea, occurs in 5%-15% of sleep apnea patients during positive airway pressure (PAP) therapy, but the clinical predictors are not well understood. The goal of this study was to explore possible predictors in a clinical sleep laboratory cohort, which may highlight those at risk during clinical management. We retrospectively analyzed 728 patients who underwent PAP titration (n=422 split-night; n=306 two-night). Demographics and self-reported medical comorbidities, medications, and behaviors as well as standard physiological parameters from the polysomnography (PSG) data were analyzed. We used regression analysis to assess predictors of binary presence or absence of central apnea index (CAI) ≥5 during split-night PSG (SN-PSG) versus full-night PSG (FN-PSG) titrations. CAI ≥5 was present in 24.2% of SN-PSG and 11.4% of FN-PSG patients during titration. Male sex, maximum continuous positive airway pressure, and use of bilevel positive airway pressure were predictors of TECSA, and rapid eye movement dominance was a negative predictor, for both SN-PSG and FN-PSG patients. Self-reported narcotics were a positive predictor of TECSA, and the time spent in stage N2 sleep was a negative predictor only for SN-PSG patients. Self-reported history of stroke and the CAI during the diagnostic recording predicted TECSA only for FN-PSG patients. Clinical predictors of treatment-evoked central apnea spanned demographic, medical history, sleep physiology, and titration factors. Improved predictive models may be increasingly important as diagnostic and therapeutic modalities move away from the laboratory setting, even as PSG remains the gold standard for characterizing primary central apnea and TECSA.

Free volume from positron lifetime and pressure-volume-temperature experiments in relation to structural relaxation of van der Waals molecular glass-forming liquids.

Science.gov (United States)

Dlubek, G; Shaikh, M Q; Rätzke, K; Paluch, M; Faupel, F

2010-06-16

Positron annihilation lifetime spectroscopy (PALS) is employed to characterize the temperature dependence of the free volume in two van der Waals liquids: 1, 1'-bis(p-methoxyphenyl)cyclohexane (BMPC) and 1, 1'-di(4-methoxy-5-methylphenyl)cyclohexane (BMMPC). From the PALS spectra analysed with the routine LifeTime9.0, the size (volume) distribution of local free volumes (subnanometer size holes), its mean, [v(h)], and mean dispersion, σ(h), were calculated. A comparison with the macroscopic volume from pressure-volume-temperature (PV T) experiments delivered the hole density and the specific hole free volume and a complete characterization of the free volume microstructure in that sense. These data are used in correlation with structural (α) relaxation data from broad-band dielectric spectroscopy (BDS) in terms of the Cohen-Grest and Cohen-Turnbull free volume models. An extension of the latter model allows us to quantify deviations between experiments and theory and an attempt to systematize these in terms of T(g) or of the fragility. The experimental data for several fragile and less fragile glass formers are involved in the final discussion. It was concluded that, for large differences in the fragility of different glass formers, the positron lifetime mirrors clearly the different character of these materials. For small differences in the fragility, additional properties like the character of bonds and chemical structure of the material may affect size, distribution and thermal behaviour of the free volume.

Free volume from positron lifetime and pressure-volume-temperature experiments in relation to structural relaxation of van der Waals molecular glass-forming liquids

Energy Technology Data Exchange (ETDEWEB)

Dlubek, G [ITA Institute for Innovative Technologies, Koethen/Halle, Wiesenring 4, D-06120 Lieskau (Germany); Shaikh, M Q; Raetzke, K; Faupel, F [Faculty of Engineering, Institute for Materials Science, Christian-Albrechts University of Kiel, Kaiserstrasse 2, D-24143 Kiel (Germany); Paluch, M, E-mail: guenter.dlubek@gmx.d [Institute of Physics, Silesian University, Uniwersytecka 4, 40-007 Katowice (Poland)

2010-06-16

Positron annihilation lifetime spectroscopy (PALS) is employed to characterize the temperature dependence of the free volume in two van der Waals liquids: 1, 1'-bis(p-methoxyphenyl)cyclohexane (BMPC) and 1, 1'-di(4-methoxy-5-methylphenyl)cyclohexane (BMMPC). From the PALS spectra analysed with the routine LifeTime9.0, the size (volume) distribution of local free volumes (subnanometer size holes), its mean, (v{sub h}), and mean dispersion, {sigma}{sub h}, were calculated. A comparison with the macroscopic volume from pressure-volume-temperature (PV T) experiments delivered the hole density and the specific hole free volume and a complete characterization of the free volume microstructure in that sense. These data are used in correlation with structural ({alpha}) relaxation data from broad-band dielectric spectroscopy (BDS) in terms of the Cohen-Grest and Cohen-Turnbull free volume models. An extension of the latter model allows us to quantify deviations between experiments and theory and an attempt to systematize these in terms of T{sub g} or of the fragility. The experimental data for several fragile and less fragile glass formers are involved in the final discussion. It was concluded that, for large differences in the fragility of different glass formers, the positron lifetime mirrors clearly the different character of these materials. For small differences in the fragility, additional properties like the character of bonds and chemical structure of the material may affect size, distribution and thermal behaviour of the free volume.

Cerebral hemodynamics in patients with obstructive sleep apnea syndrome monitored with near-infrared spectroscopy (NIRS) during positive airways pressure (CPAP) therapy: a pilot study

Science.gov (United States)

Zhang, Zhongxing; Schneider, Maja; Laures, Marco; Fritschi, Ursula; Lehner, Isabella; Qi, Ming; Khatami, Ramin

2014-03-01

In obstructive sleep apnea syndrome (OSA) the periodic reduction or cessation of breathing due to narrowing or occlusion of the upper airway during sleep leads to daytime symptoms and increased cardiovascular risk, including stroke. The higher risk of stroke is related to the impairment in cerebral vascular autoregulation. Continuous positive airways pressure (CPAP) therapy at night is the most effective treatment for OSA. However, there is no suitable bedside monitoring method evaluating the treatment efficacy of CPAP therapy, especially to monitor the recovery of cerebral hemodynamics. NIRS is ideally suited for non-invasive monitoring the cerebral hemodynamics during sleep. In this study, we will for first time assess dynamic changes of cerebral hemodynamics during nocturnal CPAP therapy in 3 patients with OSA using NIRS. We found periodic oscillations in HbO2, HHb, tissue oxygenation index (TOI) and blood volume associated with periodic apnea events without CPAP in all OSA patients. These oscillations were gradually attenuated and finally eliminated with the stepwise increments of CPAP pressures. The oscillations were totally eliminated in blood volume earlier than in other hemodynamic parameters. These results suggested that 1) the cerebral hemodynamic oscillations induced by OSA events can effectively be attenuated by CPAP therapy, and 2) blood flow and blood volume recovered first during CPAP therapy, followed by the recovery of oxygen consumption. Our study suggested that NIRS is a useful tool to evaluate the efficacy of CPAP therapy in patients with OSA bedside and in real time.

Effects of nasal positive expiratory pressure on dynamic hyperinflation and 6-minute walk test in patients with COPD.

Science.gov (United States)

Wibmer, Thomas; Rüdiger, Stefan; Heitner, Claudia; Kropf-Sanchen, Cornelia; Blanta, Ioanna; Stoiber, Kathrin M; Rottbauer, Wolfgang; Schumann, Christian

2014-05-01

Dynamic hyperinflation is an important target in the treatment of COPD. There is increasing evidence that positive expiratory pressure (PEP) could reduce dynamic hyperinflation during exercise. PEP application through a nasal mask and a flow resistance device might have the potential to be used during daily physical activities as an auxiliary strategy of ventilatory assistance. The aim of this study was to determine the effects of nasal PEP on lung volumes during physical exercise in patients with COPD. Twenty subjects (mean ± SD age 69.4 ± 6.4 years) with stable mild-to-severe COPD were randomized to undergo physical exercise with nasal PEP breathing, followed by physical exercise with habitual breathing, or vice versa. Physical exercise was induced by a standard 6-min walk test (6 MWT) protocol. PEP was applied by means of a silicone nasal mask loaded with a fixed-orifice flow resistor. Body plethysmography was performed immediately pre-exercise and post-exercise. Differences in mean pre- to post-exercise changes in total lung capacity (-0.63 ± 0.80 L, P = .002), functional residual capacity (-0.48 ± 0.86 L, P = .021), residual volume (-0.56 ± 0.75 L, P = .004), S(pO2) (-1.7 ± 3.4%, P = .041), and 6 MWT distance (-30.8 ± 30.0 m, P = .001) were statistically significant between the experimental and the control interventions. The use of flow-dependent expiratory pressure, applied with a nasal mask and a PEP device, might promote significant reduction of dynamic hyperinflation during walking exercise. Further studies are warranted addressing improvements in endurance performance under regular application of nasal PEP during physical activities.

Airway pressure release ventilation and biphasic positive airway pressure: a systematic review of definitional criteria.

Science.gov (United States)

Rose, Louise; Hawkins, Martyn

2008-10-01

The objective of this study was to identify the definitional criteria for the pressure-limited and time-cycled modes: airway pressure release ventilation (APRV) and biphasic positive airway pressure (BIPAP) available in the published literature. Systematic review. Medline, PubMed, Cochrane, and CINAHL databases (1982-2006) were searched using the following terms: APRV, BIPAP, Bilevel and lung protective strategy, individually and in combination. Two independent reviewers determined the paper eligibility and abstracted data from 50 studies and 18 discussion articles. Of the 50 studies, 39 (78%) described APRV, and 11 (22%) described BIPAP. Various study designs, populations, or outcome measures were investigated. Compared to BIPAP, APRV was described more frequently as extreme inverse inspiratory:expiratory ratio [18/39 (46%) vs. 0/11 (0%), P = 0.004] and used rarely as a noninverse ratio [2/39 (5%) vs. 3/11 (27%), P = 0.06]. One (9%) BIPAP and eight (21%) APRV studies used mild inverse ratio (>1:1 to branding may further add to confusion. Generic naming of modes and consistent definitional parameters may improve consistency of patient response for a given mode and assist with clinical implementation.

Value and limitations of transpulmonary pressure calculations during intra-abdominal hypertension.

Science.gov (United States)

Cortes-Puentes, Gustavo A; Gard, Kenneth E; Adams, Alexander B; Faltesek, Katherine A; Anderson, Christopher P; Dries, David J; Marini, John J

2013-08-01

To clarify the effect of progressively increasing intra-abdominal pressure on esophageal pressure, transpulmonary pressure, and functional residual capacity. Controlled application of increased intra-abdominal pressure at two positive end-expiratory pressure levels (1 and 10 cm H2O) in an anesthetized porcine model of controlled ventilation. Large animal laboratory of a university-affiliated hospital. Eleven deeply anesthetized swine (weight 46.2 ± 6.2 kg). Air-regulated intra-abdominal hypertension (0-25 mm Hg). Esophageal pressure, tidal compliance, bladder pressure, and end-expiratory lung aeration by gas dilution. Functional residual capacity was significantly reduced by increasing intra-abdominal pressure at both positive end-expiratory pressure levels (p ≤ 0.0001) without corresponding changes of end-expiratory esophageal pressure. Above intra-abdominal pressure 5 mm Hg, plateau airway pressure increased linearly by ~ 50% of the applied intra-abdominal pressure value, associated with commensurate changes of esophageal pressure. With tidal volume held constant, negligible changes occurred in transpulmonary pressure due to intra-abdominal pressure. Driving pressures calculated from airway pressures alone (plateau airway pressure--positive end-expiratory pressure) did not equate to those computed from transpulmonary pressure (tidal changes in transpulmonary pressure). Increasing positive end-expiratory pressure shifted the predominantly negative end-expiratory transpulmonary pressure at positive end-expiratory pressure 1 cm H2O (mean -3.5 ± 0.4 cm H2O) into the positive range at positive end-expiratory pressure 10 cm H2O (mean 0.58 ± 1.2 cm H2O). Despite its insensitivity to changes in functional residual capacity, measuring transpulmonary pressure may be helpful in explaining how different levels of positive end-expiratory pressure influence recruitment and collapse during tidal ventilation in the presence of increased intra-abdominal pressure and in

Auto-trilevel versus bilevel positive airway pressure ventilation for hypercapnic overlap syndrome patients.

Science.gov (United States)

Su, Mei; Huai, De; Cao, Juan; Ning, Ding; Xue, Rong; Xu, Meijie; Huang, Mao; Zhang, Xilong

2018-03-01

Although bilevel positive airway pressure (Bilevel PAP) therapy is usually used for overlap syndrome (OS), there is still a portion of OS patients in whom Bilevel PAP therapy could not simultaneously eliminate residual apnea events and hypercapnia. The current study was expected to explore whether auto-trilevel positive airway pressure (auto-trilevel PAP) therapy with auto-adjusting end expiratory positive airway pressure (EEPAP) can serve as a better alternative for these patients. From January of 2014 to June of 2016, 32 hypercapnic OS patients with stable chronic obstructive pulmonary diseases (COPD) and moderate-to-severe obstructive sleep apnea syndrome (OSAS) were recruited. Three variable modes of positive airway pressure (PAP) from the ventilator (Prisma25ST, Weinmann Inc., Germany) were applicated for 8 h per night. We performed the design of each mode at each night with an interval of two nights with no PAP treatment as a washout period among different modes. In Bilevel-1 mode (Bilevel-1), the expiratory positive airway pressure (EPAP) delivered from Bilevel PAP was always set as the lowest PAP for abolishment of snoring. For each patient, the inspiratory positive airway pressure (IPAP) was constantly set the same as the minimal pressure for keeping end-tidal CO 2 (ETCO 2 ) ≤45 mmHg for all three modes. However, the EPAP issued by Bilevel PAP in Bilevel-2 mode (Bilevel-2) was kept 3 cmH 2 O higher than that in Bilevel-1. In auto-trilevel mode (auto-trilevel) with auto-trilevel PAP, the initial part of EPAP was fixed at the same PAP as that in Bilevel-1 while the EEPAP was automatically regulated to rise at a range of ≤4 cmH 2 O based on nasal airflow wave changes. Comparisons were made for parameters before and during or following treatment as well as among different PAP therapy modes. The following parameters were compared such as nocturnal apnea hypopnea index (AHI), minimal SpO 2 (minSpO 2 ), arousal index, sleep structure and efficiency

Path-integral simulation of ice Ih: The effect of pressure

Science.gov (United States)

Herrero, Carlos P.; Ramírez, Rafael

2011-12-01

The effect of pressure on structural and thermodynamic properties of ice Ih has been studied by means of path-integral molecular dynamics simulations at temperatures between 50 and 300 K. Interatomic interactions were modeled by using the effective q-TIP4P/F potential for flexible water. Positive (compression) and negative (tension) pressures have been considered, which allowed us to approach the limits for the mechanical stability of this solid water phase. We have studied the pressure dependence of the crystal volume, bulk modulus, interatomic distances, atomic delocalization, and kinetic energy. The spinodal point at both negative and positive pressures is derived from the vanishing of the bulk modulus. For P300 K. At positive pressure the spinodal is associated with ice amorphization, and at low temperatures it is found to be between 1.1 and 1.3 GPa. Quantum nuclear effects cause a reduction of the metastability region of ice Ih.

Effects of diluents on soot surface temperature and volume fraction in diluted ethylene diffusion flames at pressure

KAUST Repository

Kailasanathan, Ranjith Kumar Abhinavam; Zhang, Ji; Fang, Tiegang; Roberts, William L.

2014-01-01

Soot surface temperature and volume fraction are measured in ethylene/air coflowing laminar diffusion flames at high pressures, diluted with one of four diluents (argon, helium, nitrogen, and carbon dioxide) using a two-color technique. Both

[Experimental evaluation of the role of the coronary sinus pressure in the regulation of coronary return volume via the coronary sinus. Surgical considerations in atrio-pulmonary diversion procedures].

Science.gov (United States)

Fantidis, P; Fernández Ruiz, M A; Madero Jarabo, R; Moreno Granados, F; Cordovilla Zurdo, G; Sanz Galeote, E

1990-11-01

In order to find out the validity of the vascular waterfall mechanism in coronary venous circulation, the role of coronary sinus pressure in the regulation of coronary return volume via the coronary sinus is studied in healthy animals. An experimental model of pressure regulation in the coronary sinus was prepared, and aortic pressure, EKG and the cardiac output (measured by thermodilution) were recorded. The return volume via the coronary sinus was measured at coronary sinus pressure of 10 or less, 15, 20, and 25 mmHg or more, for a total of 36 determinations. Increased coronary sinus pressure did not produce significant changes in aortic pressure, heart rate, cardiac index or coronary return volume via coronary sinus. When coronary sinus pressure was 25 mmHg or more, there was a significant decline in the average of coronary return volume via coronary sinus. Nevertheless, stepwise variant regression showed that the coronary sinus pressure per se does not condition the volume of coronary return via the coronary sinus. Our results suggest that in the healthy animals, the vascular waterfall mechanism in coronary venous circulation is not valid. Our results suggest that in the correction of congenital cardiac malformations using atriopulmonary anastomosis procedures, employing techniques that ensure coronary sinus drainage into the left atrium, in order to avoid the hemodynamic repercussions attributable to the vascular waterfall mechanism, is not justified.

Impact of pore-pressure cycling on bentonite in constant volume experiments

International Nuclear Information System (INIS)

Graham, C.C.; Harrington, J.F.; Cuss, R.J.; Sellin, P.

2012-01-01

Document available in extended abstract form only. The SKB safety case for a KBS-3 repository highlights the potential importance of future successive glaciation events on repository functions. One particular uncertainty is the likely affect of elevated pore-water pressures on barrier safety functions. Over the repository lifetime such changes in pore-water pressure are likely to be cyclic in nature, as successive glacial episodes lead to loading and unloading of the engineered barrier. For a clay-water system with the pore-water in thermodynamic equilibrium with an external reservoir of water at pressure, p w , the total stress acting on the surrounding vessel can be expressed as: (1) σ = Π + αp w where Π is the swelling pressure and α is a proportionality constant. We present results from a series of laboratory experiments designed to investigate this relationship, in the context of glacial loading. Blocks of pre-compacted Mx80 bentonite were manufactured by Clay Technology AB (Lund, Sweden), by rapidly compacting bentonite granules in a mould under a one dimensionally applied stress (Johannesson et al., 1995). The blocks were then sub-sampled and cylindrical specimens prepared for testing (120 mm in length and 60 mm in diameter). The experiments were conducted using a specially designed constant volume cell, which allows the evolution of the total stresses acting on the surrounding vessel to be monitored during clay swelling (at three radial and two axial locations). A high precision syringe pump was used to maintain a constant applied pore pressure within the bentonite, while the rate of hydraulic inflow, and consequent stress development, were monitored to determine the point at which hydraulic equilibrium was reached. During the tests each sample was subjected to an incremental series of constant pore-pressure steps, with all samples experiencing at least one loading and unloading cycle. The resulting average total stress data yield alpha values in the

Variations of Blood Pressure in Stroke Unit Patients May Result from Alternating Body Positions

NARCIS (Netherlands)

Aries, M.J.H.; Elting, Jan Willem; Stewart, Roy E.; de Keyser, Jacques; Thien, Theo; Kremer, Berry P.; Vroomen, Patrick C. A. J.

Background: Blood pressure (BP) is one of the major vital parameters monitored in the stroke unit. The accuracy of indirect BP measurement is strongly influenced by the position of both patient and arm during the measurement. Acute stroke patients are often nursed in lateral decubitus positions. The

Gas permeation measurement under defined humidity via constant volume/variable pressure method

KAUST Repository

Jan Roman, Pauls

2012-02-01

Many industrial gas separations in which membrane processes are feasible entail high water vapour contents, as in CO 2-separation from flue gas in carbon capture and storage (CCS), or in biogas/natural gas processing. Studying the effect of water vapour on gas permeability through polymeric membranes is essential for materials design and optimization of these membrane applications. In particular, for amine-based CO 2 selective facilitated transport membranes, water vapour is necessary for carrier-complex formation (Matsuyama et al., 1996; Deng and Hägg, 2010; Liu et al., 2008; Shishatskiy et al., 2010) [1-4]. But also conventional polymeric membrane materials can vary their permeation behaviour due to water-induced swelling (Potreck, 2009) [5]. Here we describe a simple approach to gas permeability measurement in the presence of water vapour, in the form of a modified constant volume/variable pressure method (pressure increase method). © 2011 Elsevier B.V.

Adherence to continuous positive airway pressure in adults with an intellectual disability

NARCIS (Netherlands)

Luijks, K.A.; Vandenbussche, N.L.; Pevernagie, D.; Overeem, S.; Pillen, S.

STUDY OBJECTIVES: This retrospective study evaluated the feasibility of continuous positive airway pressure (CPAP) therapy in adults with intellectual disabilities (ID). METHODS: CPAP therapy of 24 obstructive sleep apnea syndrome (OSA) patients with ID were compared to age- and sex-matched adults

Modified swelling pressure apparatus using vapor pressure technique for compacted bentonite

International Nuclear Information System (INIS)

Nishimura, Tomoyoshi

2012-01-01

to measure swelling pressure in a constant relative humidity environment. A relative humidity was created using salt solutions. The total volume of compacted bentonite was maintained constant during absorption process. Change of swelling pressure with elapsed time and influences of suction value are discussed in this study. In addition, unconfined compression tests were conducted for compacted bentonite with three difference suction values. Deformation of both height and diameter for samples due to change of suction were measured before shear tests. It was observed that all samples were occurred large cracks at failure condition. The shear strengths were determined from stress and strain curves Sodium bentonite was in for this test program. The specimen was statically compacted in rigid steel mold. The modified SWCC apparatus was used for soil-water characteristic curve from 0 kPa to 450 kPa in matric suction ranges. The modified SWCC apparatus consist of a triaxial chamber, air apply system, basement with ceramic filter, drain measurement system and consolidation pressure loading system. The ceramic filter had an air entry value of 500 kPa. Absorption was allowed from the top surface portion of compacted bentonite during swelling under constant volume condition. The swelling pressure was measured over two months. After swelling pressure equilibrium, the SWCC test was performed using axis-translation technique. The vertical deformation and drainage of bentonite were measured during applying ambience positive air pressure. Degree of saturation of compacted bentonite was calculated with suctions. The vapor pressure technique was conducted for high soil suction ranges. The range is from 2.8 MPa to 296 MPa corresponding to from RH 98 % to RH 11 %. The diameter and height of compacted bentonite were directly measured for determination of degree of saturation. The swelling pressure tests were conducted using newly swelling pressure test apparatus. The apparatus consisted

Effect of different seated positions on lung volume and oxygenation in acute respiratory distress syndrome.

Science.gov (United States)

Dellamonica, J; Lerolle, N; Sargentini, C; Hubert, S; Beduneau, G; Di Marco, F; Mercat, A; Diehl, J L; Richard, J C M; Bernardin, G; Brochard, L

2013-06-01

Lung volume available for ventilation is markedly decreased during acute respiratory distress syndrome. Body positioning may contribute to increase lung volume and partial verticalization is simple to perform. This study evaluated whether verticalization had parallel effects on oxygenation and end expiratory lung volume (EELV). Prospective multicenter study in 40 mechanically ventilated patients with ALI/ARDS in five university hospital MICUs. We evaluated four 45-min successive trunk position epochs (supine slightly elevated at 15°; semi recumbent with trunk elevated at 45°; seated with trunk elevated at 60° and legs down at 45°; back to supine). Arterial blood gases, EELV measured using the nitrogen washin/washout, and static compliance were measured. Responders were defined by a PaO₂/FiO₂ increase >20 % between supine and seated position. Results are median [25th-75th percentiles]. With median PEEP = 10 cmH₂O, verticalization increased lung volume but only responders (13 patients, 32 %) had a significant increase in EELV/PBW (predicted body weight) compared to baseline. This increase persisted at least partially when patients were positioned back to supine. Responders had a lower EELV/PBW supine [14 mL/kg (13-15) vs. 18 mL/kg (15-27) (p = 0.005)] and a lower compliance [30 mL/cmH₂O (22-38) vs. 42 (30-46) (p = 0.01)] than non-responders. Strain decreased with verticalization for responders. EELV/PBW increase and PaO₂/FiO₂ increase were not correlated. Verticalization is easily achieved and improves oxygenation in approximately 32 % of the patients together with an increase in EELV. Nonetheless, effect of verticalization on EELV/PBW is not predictable by PaO₂/FiO₂ increase, its monitoring may be helpful for strain optimization.

Pressure fluctuation analysis for charging pump of chemical and volume control system of nuclear power plant

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Chen Qiang

2016-01-01

Full Text Available Equipment Failure Root Cause Analysis (ERCA methodology is employed in this paper to investigate the root cause for charging pump’s pressure fluctuation of chemical and volume control system (RCV in pressurized water reactor (PWR nuclear power plant. RCA project task group has been set up at the beginning of the analysis process. The possible failure modes are listed according to the characteristics of charging pump’s actual pressure fluctuation and maintenance experience during the analysis process. And the failure modes are analysed in proper sequence by the evidence-collecting. It suggests that the gradually untightened and loosed shaft nut in service should be the root cause. And corresponding corrective actions are put forward in details.

Study of emission of a volume nanosecond discharge plasma in xenon, krypton and argon at high pressures

International Nuclear Information System (INIS)

Baksht, E Kh; Lomaev, Mikhail I; Rybka, D V; Tarasenko, Viktor F

2006-01-01

The emission properties of a volume nanosecond discharge plasma produced in xenon, krypton and argon at high pressures in a discharge gap with a cathode having a small radius of curvature are studied. Spectra in the range 120-850 nm and amplitude-time characteristics of xenon emission at different regimes and excitation techniques are recorded and analysed. It is shown that upon excitation of the volume discharge initiated by a beam of avalanche electrons, at least 90% of the energy in the spectral range 120-850 nm is emitted by xenon dimers. For xenon at a pressure of 1.2 atm, ∼45 mJ of the spontaneous emission energy was obtained in the full solid angle in a pulse with the full width at half-maximum ∼130 ns. (laser applications and other topics in quantum electronics)

Electro-mechanical probe positioning system for large volume plasma device

Science.gov (United States)

Sanyasi, A. K.; Sugandhi, R.; Srivastava, P. K.; Srivastav, Prabhakar; Awasthi, L. M.

2018-05-01

An automated electro-mechanical system for the positioning of plasma diagnostics has been designed and implemented in a Large Volume Plasma Device (LVPD). The system consists of 12 electro-mechanical assemblies, which are orchestrated using the Modbus communication protocol on 4-wire RS485 communications to meet the experimental requirements. Each assembly has a lead screw-based mechanical structure, Wilson feed-through-based vacuum interface, bipolar stepper motor, micro-controller-based stepper drive, and optical encoder for online positioning correction of probes. The novelty of the system lies in the orchestration of multiple drives on a single interface, fabrication and installation of the system for a large experimental device like the LVPD, in-house developed software, and adopted architectural practices. The paper discusses the design, description of hardware and software interfaces, and performance results in LVPD.

Short-term effects of positive expiratory airway pressure in patients being weaned from mechanical ventilation

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Marcelo de Mello Rieder

2009-05-01

Full Text Available OBJECTIVE: To investigate the feasibility and the cardiorespiratory effects of using positive expiratory airway pressure, a physiotherapeutic tool, in comparison with a T-tube, to wean patients from mechanical ventilation. METHODS/DESIGN: A prospective, randomized, cross-over study. SETTING: Two intensive care units. PATIENTS AND INTERVENTIONS: We evaluated forty patients who met weaning criteria and had been mechanically-ventilated for more than 48 hours, mean age 59 years, including 23 males. All patients were submitted to the T-tube and Expiratory Positive Airway Pressure devices, at 7 cm H2O, during a 30-minute period. Cardiorespiratory variables including work of breathing, respiratory rate (rr, peripheral oxygen saturation (SpO2, heart rate (hr, systolic, diastolic and mean arterial pressures (SAP, DAP, MAP were measured in the first and thirtieth minutes. The condition was analyzed as an entire sample set (n=40 and was also divided into subconditions: chronic obstructive pulmonary disease (n=14 and non-chronic obstructive pulmonary disease (non- chronic obstructive pulmonary disease (n=26 categories. Comparisons were made using a t-test and Analysis of Variance. The level of significance was p < 0.05. RESULTS: Our data showed an increase in work of breathing in the first and thirtieth minutes in the EPAP condition (0.86+ 0.43 and 1.02+1.3 as compared with the T-tube condition (0.25+0.26 and 0.26+0.35 (p<0.05, verified by the flow-sensor monitor (values in J/L. No statistical differences were observed when comparing the Expiratory Positive Airway Pressure and T-tube conditions with regard to cardiorespiratory measurements. The same result was observed for both chronic obstructive pulmonary disease and non- chronic obstructive pulmonary disease subconditions. CONCLUSIONS: Our study demonstrated that, in weaning patients from mechanical ventilation, the use of a fixed level of Expiratory Positive Airway Pressure caused an increase in work of

Daily Prostate Volume and Position Monitoring Using Implanted Gold Markers and On-Board Imaging during Radiotherapy

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Linda Kašaová

2011-01-01

Full Text Available Purpose: This study aimed to evaluate prostate volume changes and prostate motions during radiotherapy. Methods: In 2010, twenty-five patients were treated for prostate cancer by external beam radiotherapy with implanted fiducial markers. Coordinates of three gold markers on kilovoltage images were calculated daily. Volume changes in target structure were observed through changes in intermarker distances. Differences in patient position between laser-tattoo alignment and gold marker localization were evaluated. Intrafraction motion was assessed by measuring marker displacement on kilovoltage images acquired before and after fraction delivery. Results: Prostate shrinkage was observed in 60% of patients. The average shrinkage was 7% of the prostate’s initial volume. Corrections after laser-tattoo alignment remained mostly below 1 cm. The difference between marker centroid position on the actual images and the planning images was 2 ± 1 mm on average. The extension of intrafraction movements was 7.6 ± 0.2 mm on average. Conclusions: In our retrospective study, the possibility for prostate volume changes during radiotherapy was revealed. Intrafraction movements turned out to be the limiting factor in safety margin reduction.

Inhibitory Effect of Nasal Intermittent Positive Pressure Ventilation on Gastroesophageal Reflux.

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Danny Cantin

Full Text Available Non-invasive intermittent positive pressure ventilation can lead to esophageal insufflations and in turn to gastric distension. The fact that the latter induces transient relaxation of the lower esophageal sphincter implies that it may increase gastroesophageal refluxes. We previously reported that nasal Pressure Support Ventilation (nPSV, contrary to nasal Neurally-Adjusted Ventilatory Assist (nNAVA, triggers active inspiratory laryngeal closure. This suggests that esophageal insufflations are more frequent in nPSV than in nNAVA. The objectives of the present study were to test the hypotheses that: i gastroesophageal refluxes are increased during nPSV compared to both control condition and nNAVA; ii esophageal insufflations occur more frequently during nPSV than nNAVA. Polysomnographic recordings and esophageal multichannel intraluminal impedance pHmetry were performed in nine chronically instrumented newborn lambs to study gastroesophageal refluxes, esophageal insufflations, states of alertness, laryngeal closure and respiration. Recordings were repeated without sedation in control condition, nPSV (15/4 cmH2O and nNAVA (~ 15/4 cmH2O. The number of gastroesophageal refluxes recorded over six hours, expressed as median (interquartile range, decreased during both nPSV (1 (0, 3 and nNAVA [1 (0, 3] compared to control condition (5 (3, 10, (p < 0.05. Meanwhile, the esophageal insufflation index did not differ between nPSV (40 (11, 61 h-1 and nNAVA (10 (9, 56 h-1 (p = 0.8. In conclusion, nPSV and nNAVA similarly inhibit gastroesophageal refluxes in healthy newborn lambs at pressures that do not lead to gastric distension. In addition, the occurrence of esophageal insufflations is not significantly different between nPSV and nNAVA. The strong inhibitory effect of nIPPV on gastroesophageal refluxes appears identical to that reported with nasal continuous positive airway pressure.

A new device for administration of continuous positive airway pressure in preterm infants: comparison with a standard nasal CPAP continuous positive airway pressure system.

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Trevisanuto, Daniele; Grazzina, Nicoletta; Doglioni, Nicoletta; Ferrarese, Paola; Marzari, Francesco; Zanardo, Vincenzo

2005-06-01

We compared the effectiveness of a new continuous positive airway pressure (CPAP) device (neonatal helmet CPAP) with a conventional nasal CPAP system in preterm neonates needing continuous distending pressure. Randomized, physiological, cross-over study in a tertiary referral, neonatal intensive care unit in a university teaching hospital. Twenty very low birth weight infants with a postnatal age greater than 24 h who were receiving nasal CPAP for apnea and/or mild respiratory distress were enrolled. CPAP delivered by neonatal helmet CPAP and nasal CPAP in random order for two subsequent 90-min periods. Were continuously measured the Neonatal Infant Pain Scale (NIPS) score, oxygen requirements, respiratory rate, heart rate, oxygen saturation, transcutaneous PO(2) (tcPO(2)) and PCO(2) (tcPCO(2)), blood pressure, and desaturations. NIPS scores were significantly lower when the infants were on the neonatal helmet CPAP than when they were on nasal CPAP (0.26+/-0.07 vs. 0.63+/-0.12). The other studied parameters did not differ between the two CPAP modes. The number of desaturations was reduced during the neonatal helmet CPAP treatment (18 vs. 32), although this difference was not significant. In this short-term physiological study the neonatal helmet CPAP appears to be as good as the golden standard for managing preterm infants needing continuous distending pressure, with enhanced tolerability. Further evaluation in a randomized clinical trial is needed to confirm these findings.

Determination of Unit Pressure Force in Material Volume in the Course of Refractory Stamping Press Moulding

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Orłowicz A.W.

2016-06-01

Full Text Available The paper presents results of assessment of the unit pressure force within the refractory material volume in the course press-moulding of stampings for refractory precast shapes. The force was evaluated with the use of physical simulation of deformation undergone by lead balls placed in the raw refractory mass subjected to pressing in a metal die. To determine the value of unit pressure force applied to the aggregate grains in the course of stamping press-moulding, physical model of deformation of a sphere induced by the uniaxial stress state was used.

Is there a correlation between operative results and change in ventricular volume after shunt placement? A study of 60 cases of idiopathic normal-pressure hydrocephalus

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Meier, U.; Graewe, A.; Hajdukova, A. [Department of Neurosurgery, Unfallkrankenhaus Berlin, Warener Strasse 7, 12683, Berlin (Germany); Paris, S.; Stockheim, D.; Mutze, S. [Department of Radiology, Unfallkrankenhaus Berlin, Warener Strasse 7, 12683, Berlin (Germany)

2003-06-01

In patients with communicating or normal-pressure hydrocephalus, ventricular volume decreases following implantation of differential pressure valves. We implanted hydrostatic (Miethke dual-switch) valves in 60 patients with normal-pressure hydrocephalus (NPH) between September 1997 and December 2001. The patients underwent CT 1 year after operation, and we measured the Evans index. Although 83% of the patients showed no change in ventricular volume as assessed by this index, 72% nevertheless showed good to excellent and 16% satisfactory clinical improvement, while 12% showed no improvement. Moderate or marked reduction in ventricular size was observed in 17%, of whom 40% of these patients showed good to excellent and 20% satisfactory clinical improvement; 40% showed unsatisfactory improvement. The favourable outcome following implantation of a hydrostatic shunt thus did not correlate with decreased ventricular volume 1 year after operation, better outcomes being observed in patients with little or no alteration in ventricular size than in those with a marked decrease. Postoperative change in ventricular volume in NPH thus does not have the same significance as in patients with high-pressure hydrocephalus. (orig.)

Is there a correlation between operative results and change in ventricular volume after shunt placement? A study of 60 cases of idiopathic normal-pressure hydrocephalus

International Nuclear Information System (INIS)

Meier, U.; Graewe, A.; Hajdukova, A.; Paris, S.; Stockheim, D.; Mutze, S.

2003-01-01

In patients with communicating or normal-pressure hydrocephalus, ventricular volume decreases following implantation of differential pressure valves. We implanted hydrostatic (Miethke dual-switch) valves in 60 patients with normal-pressure hydrocephalus (NPH) between September 1997 and December 2001. The patients underwent CT 1 year after operation, and we measured the Evans index. Although 83% of the patients showed no change in ventricular volume as assessed by this index, 72% nevertheless showed good to excellent and 16% satisfactory clinical improvement, while 12% showed no improvement. Moderate or marked reduction in ventricular size was observed in 17%, of whom 40% of these patients showed good to excellent and 20% satisfactory clinical improvement; 40% showed unsatisfactory improvement. The favourable outcome following implantation of a hydrostatic shunt thus did not correlate with decreased ventricular volume 1 year after operation, better outcomes being observed in patients with little or no alteration in ventricular size than in those with a marked decrease. Postoperative change in ventricular volume in NPH thus does not have the same significance as in patients with high-pressure hydrocephalus. (orig.)

The effect of patient position and field configuration on lung volume in the treatment of advanced carcinoma of the breast or lung volumes in breast techniques - a case study

International Nuclear Information System (INIS)

Floyd, J.L.

1989-01-01

The position of the patient together with the configuration of the treatment fields play an important role in the volume of lung irradiated in breast techniques. These factors are even more important when the staging of the disease is advanced. A comparison of lung volumes is made with the patient in three treatment positions, and the effect of beam angling is demonstrated. A method of calculating the approximated lung volume from port films is proposed, together with a comparative analysis of the data obtained. Clinical decisions affecting technical considerations are examined. 6 refs., 5 figs

Capacity Decay Mitigation by Asymmetric Positive/Negative Electrolyte Volumes in Vanadium Redox Flow Batteries.

Science.gov (United States)

Park, Jong Ho; Park, Jung Jin; Park, O Ok; Yang, Jung Hoon

2016-11-23

Capacity decay in vanadium redox flow batteries during charge-discharge cycling has become an important issue because it lowers the practical energy density of the battery. The battery capacity tends to drop rapidly within the first tens of cycles and then drops more gradually over subsequent cycles during long-term operation. This paper analyzes and discusses the reasons for this early capacity decay. The imbalanced crossover rate of vanadium species was found to remain high until the total difference in vanadium concentration between the positive and negative electrolytes reached almost 1 mol dm -3 . To minimize the initial crossover imbalance, we introduced an asymmetric volume ratio between the positive and negative electrolytes during cell operation. Changing this ratio significantly reduced the capacity fading rate of the battery during the early cycles and improved its capacity retention at steady state. As an example, the practical energy density of the battery increased from 15.5 to 25.2 Wh L -1 simply after reduction of the positive volume by 25 %. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nitroglycerine and patient position effect on central, hepatic and portal venous pressures during liver surgery.

Science.gov (United States)

Sand, L; Lundin, S; Rizell, M; Wiklund, J; Stenqvist, O; Houltz, E

2014-09-01

To reduce blood loss during liver surgery, a low central venous pressure (CVP) is recommended. Nitroglycerine (NG) with its rapid onset and offset can be used to reduce CVP. In this study, the effect of NG on portal and hepatic venous pressures (PVP and HVP) in different body positions was assessed. Thirteen patients undergoing liver resection were studied. Cardiac output (CO), mean arterial pressure (MAP) and CVP were measured. PVP and HVP were measured using tip manometer catheters at baseline (BL) in horizontal position; during NG infusion, targeting a MAP of 60 mmHg, with NG infusion and the patient placed in 10 head-down position. NG infusion reduced HVP from 9.7 ± 2.4 to 7.2 ± 2.4, PVP from 12.3 ± 2.2 to 9.7 ± 3.0 and CVP from 9.8 ± 1.9 to 7.2 ± 2.1 mmHg at BL. Head-down tilt during ongoing NG resulted in increases in HVP to 8.2 ± 2.1, PVP to 10.7 ± 3 and CVP to 11 ± 1.9 mmHg. CO at BL was 6.3 ± 1.1, which was reduced by NG to 5.8 ± 1.2. Head-down tilt together with NG infusion restored CO to 6.3 ± 1.0 l/min. NG infusion leads to parallel reductions in CVP, HVP and PVP at horizontal body position. Thus, CVP can be used to guide NG dosage and fluid administration at horizontal position. NG infusion can be used to reduce HVP. Head-down tilt can be used during NG infusion to improve both blood pressure and CO without substantial increase in liver venous pressure. In head-down tilt, CVP dissociates from HVP and PVP. © 2014 The Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Densities and apparent molar volumes of HClO4(aq) and Yb(ClO4)3(aq) at elevated temperatures and pressures

International Nuclear Information System (INIS)

Hakin, Andrew W.; Lukacs, Michael J.; Jin Lianliu

2004-01-01

Relative densities have been measured for acidified aqueous solutions of ytterbium perchlorate {Yb(ClO 4 ) 3 } at approximately T=(348.15, 373.15, 398.15, and 423.15) K and p=(10.0, 20.0, and 30.0) MPa over the concentration range 0.01624≤m 2 /(mol · kg -1 ) ≤ 0.2531 using an optically coupled vibrating tube densimeter (OCVTD). Experimental apparent molar volumes have been calculated from the density measurements, and apparent molar volumes for the aqueous perchlorate salt have been calculated using Young's rule. The application of Young's rule requires apparent molar volumes for aqueous perchloric acid (HClO 4 ) solutions over extended temperature and pressure ranges. These values were calculated from densities for aqueous HClO 4 solutions that were measured using the OCVTD at the same temperatures and pressures as those used to investigate the density surface of the acidified aqueous Yb(ClO 4 ) 3 solutions. The temperature, pressure, and composition surfaces of the apparent molar volumes for Yb(ClO 4 ) 3 (aq) and HClO 4 (aq) have been modelled using Pitzer ion-interaction equations. Apparent molar volumes at infinite dilution obtained from these models have been compared to those which can be calculated using the semi-empirical Helgeson, Kirkham, and Flowers equations of state. Values for the apparent molar volume at infinite dilution of the ytterbium trivalent cation have also been calculated using simple additivity principles

Positive end-expiratory pressure improves gas exchange and pulmonary mechanics during partial liquid ventilation.

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Kirmse, M; Fujino, Y; Hess, D; Kacmarek, R M

1998-11-01

Partial liquid ventilation (PLV) with perflubron (PFB) has been proposed as an adjunct to the current therapies for the acute respiratory distress syndrome (ARDS). Because PFB has been also referred to as "liquid PEEP," distributing to the most gravity-dependent regions of the lung, less attention has been paid to the amount of applied positive end-expiratory pressure (PEEP). We hypothesized that higher PEEP levels than currently applied are needed to optimize gas exchange, and that the lower inflection point (LIP) of the pressure-volume curve could be used to estimate the amount of PEEP needed when the lung is filled with PFB. Lung injury was induced in 23 sheep by repeated lung lavage with warmed saline until the PaO2/FIO2 ratio fell below 150. Five sheep were used to investigate the change of the LIP when the lung was filled with PFB in increments of 5 ml/kg/body weight to a total of 30 ml/kg/body weight. To evaluate the impact of PEEP set at LIP +1 cm H2O we randomized an additional 15 sheep to three groups with different doses (7.5 ml, 15 ml, 30 ml/kg/body weight) of PFB. In random order a PEEP of 5 cm H2O or PEEP at LIP +1 cm H2O was applied. The LIP decreased with incremental filling of PFB to a minimum at 10 ml (p PFB shifts the LIP to the left, and that setting PEEP at LIP +1 cm H2O improves gas exchange at moderate to high doses of PFB.

Subject positioning in the BOD POD® only marginally affects measurement of body volume and estimation of percent body fat in young adult men.

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Maarten W Peeters

Full Text Available INTRODUCTION: The aim of the study was to evaluate whether subject positioning would affect the measurement of raw body volume, thoracic gas volume, corrected body volume and the resulting percent body fat as assessed by air displacement plethysmography (ADP. METHODS: Twenty-five young adult men (20.7±1.1 y, BMI = 22.5±1.4 kg/m(2 were measured using the BOD POD® system using a measured thoracic gas volume sitting in a 'forward bent' position and sitting up in a straight position in random order. RESULTS: Raw body volume was 58±124 ml (p<0.05 higher in the 'straight' position compared to the 'bent' position. The mean difference in measured thoracic gas volume (bent-straight = -71±211 ml was not statistically significant. Corrected body volume and percent body fat in the bent position consequently were on average 86±122 ml (p<0.05 and 0.5±0.7% (p<0.05 lower than in the straight position respectively. CONCLUSION: Although the differences reached statistical significance, absolute differences are rather small. Subject positioning should be viewed as a factor that may contribute to between-test variability and hence contribute to (inprecision in detecting small individual changes in body composition, rather than a potential source of systematic bias. It therefore may be advisable to pay attention to standardizing subject positioning when tracking small changes in PF are of interest. The cause of the differences is shown not to be related to changes in the volume of isothermal air in the lungs. It is hypothesized and calculated that the observed direction and magnitude of these differences may arise from the surface area artifact which does not take into account that a subject in the bent position exposes more skin to the air in the device therefore potentially creating a larger underestimation of the actual body volume due to the isothermal effect of air close to the skin.

Positive airway pressure treatment

Science.gov (United States)

... it. After using PAP regularly, you may notice: Better concentration and memory Feeling more alert and less sleepy during the day Improved sleep for your bed partner Being more productive at ... and a better mood Normal sleep patterns Lower blood pressure (in ...

Sibutramine versus continuous positive airway pressure in obese obstructive sleep apnoea patients.

Science.gov (United States)

Ferland, A; Poirier, P; Sériès, F

2009-09-01

The aim of the present study was to compare the efficacy of 1 yr of sibutramine-induced weight loss versus continuous positive airway pressure (CPAP) treatment on sleep-disordered breathing, cardiac autonomic function and systemic blood pressure in obese patients with obstructive sleep apnoea. Subjects with a body mass index of > or =30 kg.m(-2) without previous treatment for obstructive sleep apnoea underwent either sibutramine (n = 22) or CPAP (n = 18) treatment for 1 yr. Sibutramine induced a 5.4+/-1.4 kg decrease in body weight compared to the CPAP group, in which no changes in anthropometric variables were observed. The CPAP treatment improved all sleep and respiratory variables, whereas sibutramine-induced weight loss improved only nocturnal arterial oxygen saturation profile. Only CPAP treatment improved night-time systolic and diastolic blood pressure and 24-h and daytime ambulatory diastolic blood pressure. Sibutramine-induced weight loss had no impact on indices of heart rate variability, whereas CPAP treatment increased daytime time domain indices. CPAP treatment for 1 yr had beneficial impacts on nocturnal breathing disturbances, and improved nocturnal oxygenation, night-time systolic and diastolic blood pressure, and daytime cardiac parasympathetic modulation. Sibutramine did not improve sleep-disordered breathing, systemic blood pressure or heart rate variability. There were no adverse effects, such as increment in blood pressure or arrhythmias, associated with this treatment regimen.

Continuous Positive Airway Pressure for Motion Management in Stereotactic Body Radiation Therapy to the Lung: A Controlled Pilot Study

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Goldstein, Jeffrey D. [Department of Radiation Oncology, Chaim Sheba Medical Center, Tel Hashomer, Tel Aviv (Israel); Lawrence, Yaacov R. [Department of Radiation Oncology, Chaim Sheba Medical Center, Tel Hashomer, Tel Aviv (Israel); Sackler School of Medicine, Tel Aviv University, Tel Aviv (Israel); Appel, Sarit; Landau, Efrat; Ben-David, Merav A.; Rabin, Tatiana; Benayun, Maoz; Dubinski, Sergey; Weizman, Noam; Alezra, Dror; Gnessin, Hila; Goldstein, Adam M.; Baidun, Khader [Department of Radiation Oncology, Chaim Sheba Medical Center, Tel Hashomer, Tel Aviv (Israel); Segel, Michael J.; Peled, Nir [Department of Pulmonary Medicine, Chaim Sheba Medical Center, Tel Hashomer, Tel Aviv (Israel); Sackler School of Medicine, Tel Aviv University, Tel Aviv (Israel); Symon, Zvi, E-mail: symonz@sheba.health.gov.il [Department of Radiation Oncology, Chaim Sheba Medical Center, Tel Hashomer, Tel Aviv (Israel); Sackler School of Medicine, Tel Aviv University, Tel Aviv (Israel)

2015-10-01

Objective: To determine the effect of continuous positive airway pressure (CPAP) on tumor motion, lung volume, and dose to critical organs in patients receiving stereotactic body radiation therapy (SBRT) for lung tumors. Methods and Materials: After institutional review board approval in December 2013, patients with primary or secondary lung tumors referred for SBRT underwent 4-dimensional computed tomographic simulation twice: with free breathing and with CPAP. Tumor excursion was calculated by subtracting the vector of the greatest dimension of the gross tumor volume (GTV) from the internal target volume (ITV). Volumetric and dosimetric determinations were compared with the Wilcoxon signed-rank test. CPAP was used during treatment if judged beneficial. Results: CPAP was tolerated well in 10 of the 11 patients enrolled. Ten patients with 18 lesions were evaluated. The use of CPAP decreased tumor excursion by 0.5 ± 0.8 cm, 0.4 ± 0.7 cm, and 0.6 ± 0.8 cm in the superior–inferior, right–left, and anterior–posterior planes, respectively (P≤.02). Relative to free breathing, the mean ITV reduction was 27% (95% confidence interval [CI] 16%-39%, P<.001). CPAP significantly augmented lung volume, with a mean absolute increase of 915 ± 432 cm{sup 3} and a relative increase of 32% (95% CI 21%-42%, P=.003), contributing to a 22% relative reduction (95% CI 13%-32%, P=.001) in mean lung dose. The use of CPAP was also associated with a relative reduction in mean heart dose by 29% (95% CI 23%-36%, P=.001). Conclusion: In this pilot study, CPAP significantly reduced lung tumor motion compared with free breathing. The smaller ITV, the planning target volume (PTV), and the increase in total lung volume associated with CPAP contributed to a reduction in lung and heart dose. CPAP was well tolerated, reproducible, and simple to implement in the treatment room and should be evaluated further as a novel strategy for motion management in radiation therapy.

Continuous Positive Airway Pressure for Motion Management in Stereotactic Body Radiation Therapy to the Lung: A Controlled Pilot Study

International Nuclear Information System (INIS)

Goldstein, Jeffrey D.; Lawrence, Yaacov R.; Appel, Sarit; Landau, Efrat; Ben-David, Merav A.; Rabin, Tatiana; Benayun, Maoz; Dubinski, Sergey; Weizman, Noam; Alezra, Dror; Gnessin, Hila; Goldstein, Adam M.; Baidun, Khader; Segel, Michael J.; Peled, Nir; Symon, Zvi

2015-01-01

Objective: To determine the effect of continuous positive airway pressure (CPAP) on tumor motion, lung volume, and dose to critical organs in patients receiving stereotactic body radiation therapy (SBRT) for lung tumors. Methods and Materials: After institutional review board approval in December 2013, patients with primary or secondary lung tumors referred for SBRT underwent 4-dimensional computed tomographic simulation twice: with free breathing and with CPAP. Tumor excursion was calculated by subtracting the vector of the greatest dimension of the gross tumor volume (GTV) from the internal target volume (ITV). Volumetric and dosimetric determinations were compared with the Wilcoxon signed-rank test. CPAP was used during treatment if judged beneficial. Results: CPAP was tolerated well in 10 of the 11 patients enrolled. Ten patients with 18 lesions were evaluated. The use of CPAP decreased tumor excursion by 0.5 ± 0.8 cm, 0.4 ± 0.7 cm, and 0.6 ± 0.8 cm in the superior–inferior, right–left, and anterior–posterior planes, respectively (P≤.02). Relative to free breathing, the mean ITV reduction was 27% (95% confidence interval [CI] 16%-39%, P<.001). CPAP significantly augmented lung volume, with a mean absolute increase of 915 ± 432 cm 3 and a relative increase of 32% (95% CI 21%-42%, P=.003), contributing to a 22% relative reduction (95% CI 13%-32%, P=.001) in mean lung dose. The use of CPAP was also associated with a relative reduction in mean heart dose by 29% (95% CI 23%-36%, P=.001). Conclusion: In this pilot study, CPAP significantly reduced lung tumor motion compared with free breathing. The smaller ITV, the planning target volume (PTV), and the increase in total lung volume associated with CPAP contributed to a reduction in lung and heart dose. CPAP was well tolerated, reproducible, and simple to implement in the treatment room and should be evaluated further as a novel strategy for motion management in radiation therapy

A two-phase debris-flow model that includes coupled evolution of volume fractions, granular dilatancy, and pore-fluid pressure

Science.gov (United States)

George, David L.; Iverson, Richard M.

2011-01-01

Pore-fluid pressure plays a crucial role in debris flows because it counteracts normal stresses at grain contacts and thereby reduces intergranular friction. Pore-pressure feedback accompanying debris deformation is particularly important during the onset of debrisflow motion, when it can dramatically influence the balance of forces governing downslope acceleration. We consider further effects of this feedback by formulating a new, depth-averaged mathematical model that simulates coupled evolution of granular dilatancy, solid and fluid volume fractions, pore-fluid pressure, and flow depth and velocity during all stages of debris-flow motion. To illustrate implications of the model, we use a finite-volume method to compute one-dimensional motion of a debris flow descending a rigid, uniformly inclined slope, and we compare model predictions with data obtained in large-scale experiments at the USGS debris-flow flume. Predictions for the first 1 s of motion show that increasing pore pressures (due to debris contraction) cause liquefaction that enhances flow acceleration. As acceleration continues, however, debris dilation causes dissipation of pore pressures, and this dissipation helps stabilize debris-flow motion. Our numerical predictions of this process match experimental data reasonably well, but predictions might be improved by accounting for the effects of grain-size segregation.

Breathing circuit compliance and accuracy of displayed tidal volume during pressure-controlled ventilation of infants: A quality improvement project.

Science.gov (United States)

Glenski, Todd A; Diehl, Carrie; Clopton, Rachel G; Friesen, Robert H

2017-09-01

Anesthesia machines have evolved to deliver desired tidal volumes more accurately by measuring breathing circuit compliance during a preuse self-test and then incorporating the compliance value when calculating expired tidal volume. The initial compliance value is utilized in tidal volume calculation regardless of whether the actual compliance of the breathing circuit changes during a case, as happens when corrugated circuit tubing is manually expanded after the preuse self-test but before patient use. We noticed that the anesthesia machine preuse self-test was usually performed on nonexpanded pediatric circuit tubing, and then the breathing circuit was subsequently expanded for clinical use. We aimed to demonstrate that performing the preuse self-test in that manner could lead to incorrectly displayed tidal volume on the anesthesia machine monitor. The goal of this quality improvement project was to change the usual practice and improve the accuracy of displayed tidal volume in infants undergoing general anesthesia. There were four stages of the project: (i) gathering baseline data about the performance of the preuse self-test and using infant and adult test lungs to measure discrepancies of displayed tidal volumes when breathing circuit compliance was changed after the initial preuse self-test; (ii) gathering clinical data during pressure-controlled ventilation comparing anesthesia machine displayed tidal volume with actual spirometry tidal volume in patients less than 10 kg before (machine preuse self-test performed while the breathing circuit was nonexpanded) and after an intervention (machine preuse self-test performed after the breathing circuit was fully expanded); (iii) performing department-wide education to help implement practice change; (iv) gathering postintervention data to determine the prevalence of proper machine preuse self-test. At constant pressure-controlled ventilation through fully expanded circuit tubing, displayed tidal volume was 83

Use of positive pressure in preoperative and intraoperative of bariatric surgery and its effect on the time of extubation

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Letícia Baltieri

2015-04-01

Full Text Available BACKGROUND AND OBJECTIVE: To investigate the influence of intraoperative and preoperative positive pressure in the time of extubation in patients undergoing bariatric surgery. METHOD: Randomized clinical trial, in which 40 individuals with a body mass index between 40 and 55 kg/m2, age between 25 and 55 years, nonsmokers, underwent bariatric surgery type Roux-en-Y gastric bypass by laparotomy and with normal preoperative pulmonary function were randomized into the following groups: G-pre (n = 10: individuals who received treatment with noninvasive positive pressure before surgery for 1 h; G-intra (n = 10: individuals who received positive end-expiratory pressure of 10 cm H2O throughout the surgical procedure; and G-control (n = 20: not received any preoperative or intraoperative intervention. Following were recorded: time between induction of anesthesia and extubation, between the end of anesthesia and extubation, duration of mechanical ventilation, and time between extubation and discharge from the post-anesthetic recovery. RESULTS: There was no statistical difference between groups. However, when applied to the Cohen coefficient, the use of positive end-expiratory pressure of 10 cm H2O during surgery showed a large effect on the time between the end of anesthesia and extubation. About this same time, the treatment performed preoperatively showed moderate effect. CONCLUSION: The use of positive end-expiratory pressure of 10 cm H2O in the intraoperative and positive pressure preoperatively, influenced the time of extubation of patients undergoing bariatric surgery.

The effect of spherical hub-nose position on pressure drop in an oscillating water column system for wave energy conversion

Energy Technology Data Exchange (ETDEWEB)

Taha, Z.; Ahmad, N.; Ghazilla, R.A.R.; Yap, H.J.; Ya, T.Y.T.; Passarella, R.; Hasanuddin, I.; Yunus, M. [Malaya Univ. (Malaysia). Centre for Product Design and Manufacturing; Sugiyono [Malaya Univ., (Malaysia). Centre for Product Design and Manufacturing; Gadjah Mada Univ. (Indonesia). Dept. of Mechanical and Industrial Engineering

2009-07-01

The use of renewable energy sources as an alternative to conventional fuels was discussed with particular reference to ocean wave energy and its potential to contribute to the energy requirements of coastal nations. Ocean wave energy has been harnessed and converted into electricity using processes and technologies that are environmentally sound. The oscillating water column (OWC) system is considered to be among the most promising technology for harnessing wave energy. This paper presented the results of a study that investigated the pressure drop in an OWC system and the effect of spherical hub-nose position in an annular duct. Computational fluid dynamics (CFD) analysis was used under steady flow conditions for several hub-nose positions to determine the characteristic of pressure drop. The study showed that the hub-nose position influenced the pressure drop in the OWC system. The highest value of the pressure drop in this study occurred when the hub-nose was at the position of 0.0 m relative to the end of the converging cone. The pressure drop decreased when the hub-nose position moved away from the end of converging cone. The lowest value occurred at the position of -0.5 m. It was concluded that despite the numerically small change in pressure drop, this phenomenon should be considered in the design process of the OWC system because of the operational condition of the system at low-pressure pneumatic power. The pressure drop actually reduces the amount of energy that will be converted by the air turbine. 9 refs., 2 tabs., 6 figs.

Thallium pulmonary scintigraphy. Relationship to pulmonary fluid volumes during left atrial hypertension and the acute release of pressure

International Nuclear Information System (INIS)

Slutsky, R.A.

1984-01-01

To evaluate the relationship between thallium-201 lung activity and pulmonary fluid volumes, we compared thallium pulmonary scintigrams with measures of intravascular (PBV), extravascular (EVLW) and total lung water (TLW) during gradual left atrial (LA) hypertension and then serially after the acute release of pressure. The study group was composed of nine mongrel dogs who were each studied at seven levels of elevated LA pressure, and then every 15 minutes for 2 hours after the acute release of pressure. During LA pressure (congestion phase) elevation, lung counts (normalized for myocardial activity), correlated best with TLW (r . .91), rather than PBV (r . .84) or EVLW (r . .81). After the release of pressure (recovery phase), lung counts correlated well with EVLW (r . .92) and TLW (r . .82), but not with PBV (r . .28). Postmortem lung counts from 197 separate lung sections correlated well with the corresponding wet weight/dry weight ratio from that section (r . .81). Thus, we conclude that changes in pulmonary thallium emissions during cardiogenic pulmonary edema relate to corresponding changes in pulmonary fluid volumes. During congestion, the confounding effects of nonlinear increases in EVLW and PBV make thallium emissions more a marker of TLW than either the intravascular or extravascular pulmonary fluid compartment. After pressure release, PBV immediately returns to normal, at which time EVLW and pulmonary emissions correlate closely. These latter data, more applicable to postexercise stress thallium data, lend support to the hypothesis that elevated pulmonary emissions during postexercise thallium scintigrams reflect elevations in EVLW that develop during exercise

Bilateral parotitis in a patient under continuous positive airway pressure treatment.

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Abdullayev, Ruslan; Saral, Filiz Cosku; Kucukebe, Omer Burak; Sayiner, Hakan Sezgin; Bayraktar, Cem; Akgun, Sadik

Many conditions such as bacterial and viral infectious diseases, mechanical obstruction due to air and calculi and drugs can cause parotitis. We present a case of unusual bilateral parotitis in a patient under non-invasive continuous positive airway pressure (CPAP) therapy for chronic obstructive pulmonary disease exacerbation in intensive care unit. A 36-year-old patient was admitted to intensive care unit with the diagnosis of chronic obstructive pulmonary disease exacerbation. Antibiotherapy, bronchodilator therapy and non-invasive positive pressure ventilation were applied as treatment regimen. Painless swellings developed on the 3rd day of admission on the right and a day after this on the left parotid glands. Amylase levels were increased and ultrasonographic evaluation revealed bilateral parotitis. No intervention was made and the therapy was continued. The patient was discharged on the 6th day with clinical improvement and regression of parotid swellings without any complications. Parotitis may have occurred after retrograde air flow in the Stensen duct during CPAP application. After the exclusion of possible viral and bacteriological etiologies and possible drug reactions we can focus on this diagnosis. Copyright © 2014 Sociedade Brasileira de Anestesiologia. Published by Elsevier Editora Ltda. All rights reserved.

Effect of volume expansion on systemic hemodynamics and central and arterial blood volume in cirrhosis

DEFF Research Database (Denmark)

Møller, S; Bendtsen, F; Henriksen, Jens Henrik Sahl

1995-01-01

, and arterial pressure were determined before and during a volume expansion induced by infusion of a hyperosmotic galactose solution. RESULTS: During volume expansion, the central and arterial blood volume increased significantly in patients with class A and controls, whereas no significant change was found...... in patients with either class B or class C. Conversely, the noncentral blood volume increased in patients with class B and C. In both patients and controls, the cardiac output increased and the systemic vascular resistance decreased, whereas the mean arterial blood pressure did not change significantly......BACKGROUND & AIMS: Systemic vasodilatation in cirrhosis may lead to hemodynamic alterations with reduced effective blood volume and decreased arterial blood pressure. This study investigates the response of acute volume expansion on hemodynamics and regional blood volumes in patients with cirrhosis...

Audiovisual biofeedback guided breath-hold improves lung tumor position reproducibility and volume consistency

Directory of Open Access Journals (Sweden)

Danny Lee, PhD

2017-07-01

Conclusions: This study demonstrated that audiovisual biofeedback can be used to improve the reproducibility and consistency of breath-hold lung tumor position and volume, respectively. These results may provide a pathway to achieve more accurate lung cancer radiation treatment in addition to improving various medical imaging and treatments by using breath-hold procedures.

The Pressure-Volume-Temperature Equation of State of Iron-Rich (Mg,Fe)O

Science.gov (United States)

Wicks, J. K.; Jackson, J. M.; Zhuravlev, K. K.; Prakapenka, V.

2012-12-01

Seismic observations near the base of the core-mantle boundary (CMB) have detected 5-20 km thick patches in which the seismic wave velocities are reduced by up to 30%. These ultra-low velocity zones (ULVZs) have been interpreted as aggregates of partially molten material (e.g. Williams and Garnero 1996, Hernlund and Jellinek, 2010) or as solid, iron-enriched residues (e.g. Knittle and Jeanloz, 1991; Mao et al., 2006; Wicks et al., 2010), typically based on proposed sources of velocity reduction. The stabilities of these structure types have been explored through dynamic models that have assembled a relationship between ULVZ stability and density (Hernlund and Tackley, 2007; Bower et al., 2010). Now, to constrain the chemistry of ULVZs, more information is needed on the relationship between density and sound velocity of candidate phases. Recently, we have shown that the characteristically low sound speeds of ULVZs can be produced by small amounts of iron-rich (Mg,Fe)O, which is likely to be found in iron-rich assemblages based on current partitioning studies (eg. Sakai et al., 2010; Tange et al., 2009). We determined the Debye velocity (VD) of (Mg.1657Fe.84)O using nuclear resonant inelastic x-ray scattering (NRIXS), and calculated the seismically relevant compressional (VP) and shear (VS) wave velocities up to 120 GPa using an equation of state of a similar composition (Wicks et al., 2010). These densities and sound velocities, in turn, are consistent with reasonable morphologies of modeled solid ULVZs (Bower et al., 2011). To increase the accuracy of density and sound velocity predictions, measurements must be made at elevated temperatures to correctly predict the properties of iron-rich (Mg,Fe)O at mantle conditions. In this study, we present the pressure-volume-temperature equation of state of (Mg.0657Fe.94)O measured up to pressures of 120 GPa and temperatures of 2000 K. Volume was measured with x-ray diffraction at beamline 13-ID-D of the Advanced Photon

High tidal volume ventilation in infant mice.

Science.gov (United States)

Cannizzaro, Vincenzo; Zosky, Graeme R; Hantos, Zoltán; Turner, Debra J; Sly, Peter D

2008-06-30

Infant mice were ventilated with either high tidal volume (V(T)) with zero end-expiratory pressure (HVZ), high V(T) with positive end-expiratory pressure (PEEP) (HVP), or low V(T) with PEEP. Thoracic gas volume (TGV) was determined plethysmographically and low-frequency forced oscillations were used to measure the input impedance of the respiratory system. Inflammatory cells, total protein, and cytokines in bronchoalveolar lavage fluid (BALF) and interleukin-6 (IL-6) in serum were measured as markers of pulmonary and systemic inflammatory response, respectively. Coefficients of tissue damping and tissue elastance increased in all ventilated mice, with the largest rise seen in the HVZ group where TGV rapidly decreased. BALF protein levels increased in the HVP group, whereas serum IL-6 rose in the HVZ group. PEEP keeps the lungs open, but provides high volumes to the entire lungs and induces lung injury. Compared to studies in adult and non-neonatal rodents, infant mice demonstrate a different response to similar ventilation strategies underscoring the need for age-specific animal models.

Successful use of non-invasive positive pressure ventilation in a complicated flail chest

International Nuclear Information System (INIS)

Al-Ansari, Mariam A.

2006-01-01

The current advanced trauma life support manual states that patients with significant hypoxia (namely, SaO2<90% on room air) as a result of pulmonary contusion should be intubated and ventilated within the first hour of injury. Recently, several researchers have shown improved outcomes when patients with acute respiratory failure are managed with noninvasive positive pressure ventilation (NIPPV). Trauma patients may also benefit from this therapy. We report a case of 15-year-old boy who isolated flail chest and pulmonary contusion, who was intubated in the emergency room, and was managed successfully with the NIPPV in the intensive care unit (ICU) despite, having had aspiration pneumonia early in the course of her stay. After initial stabilization, he failed a spontaneous breathing trial. Due to absence of contraindications to the use of NIPPV, the patient was extubated on day 7 (from pressure ventilation of 15 cmH2O and positive end expiratory pressure of 8 cm H2O) to immediate NIPPV use. Three days later (after a total of 50 hours of NIPPV use in the ICU) the patient was successfully discharged home. (author)

Clinical predictors of central sleep apnea evoked by positive airway pressure titration

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Moro M

2016-07-01

Full Text Available Marilyn Moro,1 Karen Gannon,1 Kathy Lovell,1 Margaret Merlino,1 James Mojica,2 Matt T Bianchi,1,3 1Neurology Department, 2Pulmonary and Critical Care Medicine, Massachusetts General Hospital, Boston, MA, USA; 3Division of Sleep Medicine, Harvard Medical School, Boston, MA, USA Purpose: Treatment-emergent central sleep apnea (TECSA, also called complex apnea, occurs in 5%–15% of sleep apnea patients during positive airway pressure (PAP therapy, but the clinical predictors are not well understood. The goal of this study was to explore possible predictors in a clinical sleep laboratory cohort, which may highlight those at risk during clinical management.Methods: We retrospectively analyzed 728 patients who underwent PAP titration (n=422 split night; n=306 two-night. Demographics and self-reported medical comorbidities, medications, and behaviors as well as standard physiological parameters from the polysomnography (PSG data were analyzed. We used regression analysis to assess predictors of binary presence or absence of central apnea index (CAI ≥5 during split PSG (SN-PSG versus full-night PSG (FN-PSG titrations.Results: CAI ≥5 was present in 24.2% of SN-PSG and 11.4% of FN-PSG patients during titration. Male sex, maximum continuous positive airway pressure, and use of bilevel positive airway pressure were predictors of TECSA, and rapid eye movement dominance was a negative predictor, for both SN-PSG and FN-PSG patients. Self-reported narcotics were a positive predictor of TECSA, and the time spent in stage N2 sleep was a negative predictor only for SN-PSG patients. Self-reported history of stroke and the CAI during the diagnostic recording predicted TECSA only for FN-PSG patients.Conclusion: Clinical predictors of treatment-evoked central apnea spanned demographic, medical history, sleep physiology, and titration factors. Improved predictive models may be increasingly important as diagnostic and therapeutic modalities move away from the

Cone Beam CT Imaging Analysis of Interfractional Variations in Bladder Volume and Position During Radiotherapy for Bladder Cancer

International Nuclear Information System (INIS)

Yee, Don; Parliament, Matthew; Rathee, Satyapal; Ghosh, Sunita; Ko, Lawrence; Murray, Brad

2010-01-01

Purpose: To quantify daily bladder size and position variations during bladder cancer radiotherapy. Methods and Materials: Ten bladder cancer patients underwent daily cone beam CT (CBCT) imaging of the bladder during radiotherapy. Bladder and planning target volumes (bladder/PTV) from CBCT and planning CT scans were compared with respect to bladder center-of-mass shifts in the x (lateral), y (anterior-posterior), and z (superior-inferior) coordinates, bladder/PTV size, bladder/PTV margin positions, overlapping areas, and mutually exclusive regions. Results: A total of 262 CBCT images were obtained from 10 bladder cancer patients. Bladder center of mass shifted most in the y coordinate (mean, -0.32 cm). The anterior bladder wall shifted the most (mean, -0.58 cm). Mean ratios of CBCT-derived bladder and PTV volumes to planning CT-derived counterparts were 0.83 and 0.88. The mean CBCT-derived bladder volume (± standard deviation [SD]) outside the planning CT counterpart was 29.24 cm 3 (SD, 29.71 cm 3 ). The mean planning CT-derived bladder volume outside the CBCT counterpart was 47.74 cm 3 (SD, 21.64 cm 3 ). The mean CBCT PTV outside the planning CT-derived PTV was 47.35 cm 3 (SD, 36.51 cm 3 ). The mean planning CT-derived PTV outside the CBCT-derived PTV was 93.16 cm 3 (SD, 50.21). The mean CBCT-derived bladder volume outside the planning PTV was 2.41 cm 3 (SD, 3.97 cm 3 ). CBCT bladder/ PTV volumes significantly differed from planning CT counterparts (p = 0.047). Conclusions: Significant variations in bladder and PTV volume and position occurred in patients in this trial.

Interfractional changes in tumour volume and position during entire radiotherapy courses for lung cancer with respiratory gating and image guidance

DEFF Research Database (Denmark)

Juhler-Nøttrup, Trine; Korreman, Stine Sofia; Pedersen, Anders N

2008-01-01

were contoured on each CT scan to evaluate the variations in volumes and position. The lung tumours and the mediastinal tumours were contoured separately. The positional variations were measured as 3D mobility vectors and correlated to matching of the scans using the two different strategies. RESULTS......-87% when matched using bony landmarks and 70-76% when matched using skin tattoos. The overlap of the mediastinal tumours were 60-65% and 41-47%, respectively. CONCLUSIONS: Despite the use of gating the tumours varied considerably, regarding both position and volume. The variations in position were...

Effects of a prostagrandin EP4-receptor agonist ONO-AE1-329 on the left ventricular pressure-volume relationship in the halothane-anesthetized dogs.

Science.gov (United States)

Honda, Atsushi; Nakamura, Yuji; Ohara, Hiroshi; Cao, Xin; Nomura, Hiroaki; Katagi, Jun; Wada, Takeshi; Izumi-Nakaseko, Hiroko; Ando, Kentaro; Sugiyama, Atsushi

2016-03-15

Cardiac effects of a prostagrandin EP4-receptor agonist ONO-AE1-329 were assessed in the halothane-anesthetized dogs under the monitoring of left ventricular pressure-volume relationship, which were compared with those of clinically recommended doses of dopamine, dobutamine and milrinone (n=4-5 for each treatment). ONO-AE1-329 was intravenously administered in doses of 0.3, 1 and 3 ng/kg/min for 10 min with a pause of 20 min. Dopamine in a dose of 3 µg/kg/min for 10 min, dobutamine in a dose of 1 µg/kg/min for 10 min and milrinone in a dose of 5 µg/kg/min for 10 min followed by 0.5 µg/kg/min for 10 min were intravenously administered. Low dose of ONO-AE1-329 increased the stroke volume. Middle dose of ONO-AE1-329 increased the cardiac output, left ventricular end-diastolic volume, ejection fraction, maximum upstroke/downstroke velocities of the left ventricular pressure and external work, but decreased the end-systolic pressure and internal work besides the change by the low dose. High dose of ONO-AE1-329 increased the heart rate and maximum elastance, but decreased the end-systolic volume besides the changes by the middle dose. Dopamine, dobutamine and milrinone exerted essentially similar cardiac effects to ONO-AE1-329, but they did not significantly change the end-diastolic volume, end-systolic volume, stroke volume, ejection fraction, end-systolic pressure, maximum elastance, external work or internal work. Thus, EP4-receptor stimulation by ONO-AE1-329 may have potential to better promote the passive ventricular filling than the conventional cardiotonic drugs, which could become a candidate of novel therapeutic strategy for the treatment of heart failure with preserved ejection fraction. Copyright © 2016 Elsevier B.V. All rights reserved.

Central venous pressure and shock index predict lack of hemodynamic response to volume expansion in septic shock: a prospective, observational study.

Science.gov (United States)

Lanspa, Michael J; Brown, Samuel M; Hirshberg, Eliotte L; Jones, Jason P; Grissom, Colin K

2012-12-01

Volume expansion is a common therapeutic intervention in septic shock, although patient response to the intervention is difficult to predict. Central venous pressure (CVP) and shock index have been used independently to guide volume expansion, although their use is questionable. We hypothesize that a combination of these measurements will be useful. In a prospective, observational study, patients with early septic shock received 10-mL/kg volume expansion at their treating physician's discretion after brief initial resuscitation in the emergency department. Central venous pressure and shock index were measured before volume expansion interventions. Cardiac index was measured immediately before and after the volume expansion using transthoracic echocardiography. Hemodynamic response was defined as an increase in a cardiac index of 15% or greater. Thirty-four volume expansions were observed in 25 patients. A CVP of 8 mm Hg or greater and a shock index of 1 beat min(-1) mm Hg(-1) or less individually had a good negative predictive value (83% and 88%, respectively). Of 34 volume expansions, the combination of both a high CVP and a low shock index was extremely unlikely to elicit hemodynamic response (negative predictive value, 93%; P = .02). Volume expansion in patients with early septic shock with a CVP of 8 mm Hg or greater and a shock index of 1 beat min(-1) mm Hg(-1) or less is unlikely to lead to an increase in cardiac index. Copyright © 2012 Elsevier Inc. All rights reserved.

Thermodynamic analysis of energy density in pressure retarded osmosis: The impact of solution volumes and costs

International Nuclear Information System (INIS)

Reimund, Kevin K.

2015-01-01

A general method was developed for estimating the volumetric energy efficiency of pressure retarded osmosis via pressure-volume analysis of a membrane process. The resulting model requires only the osmotic pressure, π, and mass fraction, w, of water in the concentrated and dilute feed solutions to estimate the maximum achievable specific energy density, uu, as a function of operating pressure. The model is independent of any membrane or module properties. This method utilizes equilibrium analysis to specify the volumetric mixing fraction of concentrated and dilute solution as a function of operating pressure, and provides results for the total volumetric energy density of similar order to more complex models for the mixing of seawater and riverwater. Within the framework of this analysis, the total volumetric energy density is maximized, for an idealized case, when the operating pressure is π(1+√w -1 ), which is lower than the maximum power density operating pressure, Δπ/2, derived elsewhere, and is a function of the solute osmotic pressure at a given mass fraction. It was also found that a minimum 1.45 kmol of ideal solute is required to produce 1 kWh of energy while a system operating at "maximum power density operating pressure" requires at least 2.9 kmol. Utilizing this methodology, it is possible to examine the effects of volumetric solution cost, operation of a module at various pressure, and operation of a constant pressure module with various feed.

Positional effects on distribution of ventilation in chronic obstructive pulmonary disease

International Nuclear Information System (INIS)

Shim, C.; Chun, K.J.; Williams, M.H. Jr.; Blaufox, M.D.

1986-01-01

Ventilation is distributed predominantly to the dependent lung in normal persons in the decubitus position. We evaluated the distribution of ventilation in four patients with mild-to-moderate chronic obstructive pulmonary disease using 81mKr gas. Patients were tested in the sitting and right and left decubitus positions with and without the application of positive end expiratory pressure (PEEP). In contrast to findings in controls, ventilation was predominantly distributed to the nondependent lung in patients in the decubitus position. Mean ventilation in the right lung decreased from 51% of the total in the sitting position to 31% in the right decubitus position; it increased with the application of 10 cm PEEP. Reduced ventilation in the dependent lung most likely is caused by closure of the airways after a decrease in volume. Application of PEEP resulted in increased lung volume and preferential distribution of ventilation to the dependent lung

Continuous positive airway pressure (CPAP).

Science.gov (United States)

Sahni, R; Wung, J T

1998-01-01

Progress in neonatal intensive care is closely linked to improvements in the management of respiratory failure in small infants. This applies to the care of the preterm infants with immature lungs, and also to treatment of the preterm or full term infants with specific diseases that are associated with respiratory failure. Respiratory distress of the newborn continues to account for significant morbidity in the intensive care unit. The spectrum of disease ranges from mild distress to severe respiratory failure requiring varying degrees of support. The current modalities of ventilatory assistance range from the more benign continuous positive airway pressure (CPAP) to conventional mechanical ventilation, and on to high frequency ventilation. It is a reasonable supposition that the type of ventilatory assistance provided to these infants should be graded according to the severity of the disease. However, the principal objective in selecting the mode of respiratory support should be to use a modality which results in minimal volo- or barotrauma to the infant. The following detailed description on CPAP explains its physiological effects, delivery system, indications for use, application, maintenance, and associated complications. The equipment described is simple to use, has a greater cost benefit, and has a more universal application, which is of help to smaller units including those in the developing parts of the world. We have also included our institutional clinical experience of CPAP usage in very low birth weight infants from the periods before and after commercial availability of surfactant in the United States.

Early predictors of success of non-invasive positive pressure ventilation in hypercapnic respiratory failure.

Science.gov (United States)

Bhattacharyya, D; Prasad, Bnbm; Tampi, P S; Ramprasad, R

2011-10-01

Non-invasive positive pressure ventilation (NIPPV) has emerged as a significant advancement in the management of acute hypercapnic respiratory failure. Patients with hypercapnic respiratory failure requiring ventilation therapy (respiratory rate [RR] of > 30 breaths per minutes, PaCO2 > 55 mmHg and arterial pH success group and these parameters continued to improve even after four and 24 hours of NIPPV treatment. Out of 24 (24%) patients who failed to respond, 13 (54%) needed endotracheal intubation within one hour. The failure group had higher baseline HR than the success group. Improvement in HR, RR, pH, and PCO2 one hour after putting the patient on NIPPV predicts success of non-invasive positive pressure ventilation in hypercapnic respiratory failure.

46 CFR 197.462 - Pressure vessels and pressure piping.

Science.gov (United States)

2010-10-01

... that each pressure vessel, including each volume tank, cylinder and PVHO, and each pressure piping... tests conducted in accordance with this section shall be either hydrostatic tests or pneumatic tests. (1... times the maximum allowable working pressure. (2) When a pneumatic test is conducted on a pressure...

Blood volume, blood pressure and total body sodium: internal signalling and output control

DEFF Research Database (Denmark)

Bie, P

2009-01-01

Total body sodium and arterial blood pressure (ABP) are mutually dependent variables regulated by complex control systems. This review addresses the role of ABP in the normal control of sodium excretion (NaEx), and the physiological control of renin secretion. NaEx is a pivotal determinant of ABP......, and under experimental conditions, ABP is a powerful, independent controller of NaEx. Blood volume is a function of dietary salt intake; however, ABP is not, at least not in steady states. A transient increase in ABP after a step-up in sodium intake could provide a causal relationship between ABP...... and the regulation of NaEx via a hypothetical integrative control system. However, recent data show that subtle sodium loading (simulating salty meals) causes robust natriuresis without changes in ABP. Changes in ABP are not necessary for natriuresis. Normal sodium excretion is not regulated by pressure. Plasma...

The effect of blood volume loss on cardiovascular response to lower body negative pressure using a mathematical model

Science.gov (United States)

Karam, E. H.; Srinivasan, R. S.; Charles, J. B.; Fortney, S. M.

1994-01-01

Different mathematical models of varying complexity have been proposed in recent years to study the cardiovascular (CV) system. However, only a few of them specifically address the response to lower body negative pressure (LBNP), a stress that can be applied in weightlessness to predict changes in orthostatic tolerance. Also, the simulated results produced by these models agree only partially with experimental observations. In contrast, the model proposed by Melchior et al., and modified by Karam et al. is a simple representation of the CV system capable of accurately reproducing observed LBNP responses up to presyncopal levels. There are significant changes in LBNP response due to a loss of blood volume and other alterations that occur in weightlessness and related one-g conditions such as bedrest. A few days of bedrest can cause up to 15% blood volume loss (BVL), with consequent decreases in both stroke volume and cardiac output, and increases in heart rate, mean arterial pressure, and total peripheral resistance. These changes are more pronounced at higher levels of LBNP. This paper presents the results of a simulation study using our CV model to examine the effect of BVL on LBNP response.

Proceedings of the 1985 pressure vessels and piping conference. Volume PVP-98-8. Fracture, fatigue and advanced mechanics

International Nuclear Information System (INIS)

Short, W.E.; Zamrik, S.Y.

1985-01-01

State-of-the-art engineering practices in pressure vessel and piping technology are the result of continual efforts in the evaluation of problems which have been experienced and the development of appropriate design and analysis methods for those applications. The resulting advances in technology benefit industry with properly engineered, safe, cost-effective pressure vessels and piping systems. To this end, advanced study continues in specialized areas of mechanical engineering such as fracture mechanics, experimental stress analysis, high pressure applications and related material considerations, as well as advanced techniques for evaluation of commonly encountered design problems. This volume is comprised of current technical papers on various aspects of fracture, fatigue and advanced mechanics as related to the design and analysis of pressure vessels and piping

Clinical assessment of auto-positive end-expiratory pressure by diaphragmatic electrical activity during pressure support and neurally adjusted ventilatory assist.

Science.gov (United States)

Bellani, Giacomo; Coppadoro, Andrea; Patroniti, Nicolò; Turella, Marta; Arrigoni Marocco, Stefano; Grasselli, Giacomo; Mauri, Tommaso; Pesenti, Antonio

2014-09-01

Auto-positive end-expiratory pressure (auto-PEEP) may substantially increase the inspiratory effort during assisted mechanical ventilation. Purpose of this study was to assess whether the electrical activity of the diaphragm (EAdi) signal can be reliably used to estimate auto-PEEP in patients undergoing pressure support ventilation and neurally adjusted ventilatory assist (NAVA) and whether NAVA was beneficial in comparison with pressure support ventilation in patients affected by auto-PEEP. In 10 patients with a clinical suspicion of auto-PEEP, the authors simultaneously recorded EAdi, airway, esophageal pressure, and flow during pressure support and NAVA, whereas external PEEP was increased from 2 to 14 cm H2O. Tracings were analyzed to measure apparent "dynamic" auto-PEEP (decrease in esophageal pressure to generate inspiratory flow), auto-EAdi (EAdi value at the onset of inspiratory flow), and IDEAdi (inspiratory delay between the onset of EAdi and the inspiratory flow). The pressure necessary to overcome auto-PEEP, auto-EAdi, and IDEAdi was significantly lower in NAVA as compared with pressure support ventilation, decreased with increase in external PEEP, although the effect of external PEEP was less pronounced in NAVA. Both auto-EAdi and IDEAdi were tightly correlated with auto-PEEP (r = 0.94 and r = 0.75, respectively). In the presence of auto-PEEP at lower external PEEP levels, NAVA was characterized by a characteristic shape of the airway pressure. In patients with auto-PEEP, NAVA, compared with pressure support ventilation, led to a decrease in the pressure necessary to overcome auto-PEEP, which could be reliably monitored by the electrical activity of the diaphragm before inspiratory flow onset (auto-EAdi).

Pharmacologic Interventions to Improve Splanchnic Oxygenation During Ventilation with Positive End-Expiratory Pressure

NARCIS (Netherlands)

Fournell, A.; Scheeren, T. W. L.; Picker, O.; Schwarte, L. A.; Wolf, M; Bucher, HU; Rudin, M; VanHuffel, S; Wolf, U; Bruley, DF; Harrison, DK

2012-01-01

Mechanical ventilation with positive end-expiratory pressure (PEEP) is an indispensable tool in the management of respiratory failure to preserve or improve lung function and systemic oxygenation. However, PEEP per se may also, as has been shown in experimental animals, impair regional

Visual evoked potentials show strong positive association with intracranial pressure in patients with cryptococcal meningitis

Directory of Open Access Journals (Sweden)

Marcelo Adriano da Cunha Silva Vieira

2015-04-01

Full Text Available Objective : To verify the relationship between intracranial pressure and flash visual evoked potentials (F-VEP in patients with cryptococcal meningitis. Method The sample included adults diagnosed with cryptococcal meningitis admitted at a reference hospital for infectious diseases. The patients were subjected to F-VEP tests shortly before lumbar puncture. The Pearson’s linear correlation coefficient was calculated and the linear regression analysis was performed. Results : Eighteen individuals were subjected to a total of 69 lumbar punctures preceded by F-VEP tests. At the first lumbar puncture performed in each patient, N2 latency exhibited a strong positive correlation with intracranial pressure (r = 0.83; CI = 0.60 - 0.94; p < 0.0001. The direction of this relationship was maintained in subsequent punctures. Conclusion : The intracranial pressure measured by spinal tap manometry showed strong positive association with the N2 latency F-VEP in patients with cryptococcal meningitis.

Thermodynamic analysis of energy density in pressure retarded osmosis: The impact of solution volumes and costs

Energy Technology Data Exchange (ETDEWEB)

Reimund, Kevin K. [Univ. of Connecticut, Storrs, CT (United States). Dept. of Chemical and Biomolecular Engineering; McCutcheon, Jeffrey R. [Univ. of Connecticut, Storrs, CT (United States). Dept. of Chemical and Biomolecular Engineering; Wilson, Aaron D. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

2015-08-01

A general method was developed for estimating the volumetric energy efficiency of pressure retarded osmosis via pressure-volume analysis of a membrane process. The resulting model requires only the osmotic pressure, π, and mass fraction, w, of water in the concentrated and dilute feed solutions to estimate the maximum achievable specific energy density, uu, as a function of operating pressure. The model is independent of any membrane or module properties. This method utilizes equilibrium analysis to specify the volumetric mixing fraction of concentrated and dilute solution as a function of operating pressure, and provides results for the total volumetric energy density of similar order to more complex models for the mixing of seawater and riverwater. Within the framework of this analysis, the total volumetric energy density is maximized, for an idealized case, when the operating pressure is π/(1+√w⁻¹), which is lower than the maximum power density operating pressure, Δπ/2, derived elsewhere, and is a function of the solute osmotic pressure at a given mass fraction. It was also found that a minimum 1.45 kmol of ideal solute is required to produce 1 kWh of energy while a system operating at “maximum power density operating pressure” requires at least 2.9 kmol. Utilizing this methodology, it is possible to examine the effects of volumetric solution cost, operation of a module at various pressure, and operation of a constant pressure module with various feed.

Food Processing Innovation: A Case Study with Pressurized Passion Fruit Juice

OpenAIRE

Lúcia Helena Laboissière; Rosires Deliza; Aline Mota Barros-Marcellini; Amauri Rosenthal; Lourdes Maria Camargo; Roberto Junqueira

2007-01-01

Tropical fruit juice production shows an annual increase in volume of 15 to 20% in Brazil. Growing demand for processed fruit pulp arouses juice industry interest to search for novel technologies. High Hydrostatic Pressure (HHP) is an innovative technology which allows juice production with improved sensory characteristics compared to pasteurization, meeting consumer demands for fresh-like foods. Despite recognized advantages of pressurized products described in the literature, a positive con...

Response of Preterm Infants to 2 Noninvasive Ventilatory Support Systems: Nasal CPAP and Nasal Intermittent Positive-Pressure Ventilation.

Science.gov (United States)

Silveira, Carmen Salum Thomé; Leonardi, Kamila Maia; Melo, Ana Paula Carvalho Freire; Zaia, José Eduardo; Brunherotti, Marisa Afonso Andrade

2015-12-01

Noninvasive ventilation (NIV) in preterm infants is currently applied using intermittent positive pressure (2 positive-pressure levels) or in a conventional manner (one pressure level). However, there are no studies in the literature comparing the chances of failure of these NIV methods. The aim of this study was to evaluate the occurrence of failure of 2 noninvasive ventilatory support systems in preterm neonates over a period of 48 h. A randomized, prospective, clinical study was conducted on 80 newborns (gestational age CPAP and 40 infants with nasal intermittent positive-pressure ventilation (NIPPV). The occurrence of apnea, progression of respiratory distress, nose bleeding, and agitation was defined as ventilation failure. The need for intubation and re-intubation after failure was also observed. There were no significant differences in birth characteristics between groups. Ventilatory support failure was observed in 25 (62.5%) newborns treated with nasal CPAP and in 12 (30%) newborns treated with NIPPV, indicating an association between NIV failure and the absence of intermittent positive pressure (odds ratio [OR] 1.22, P CPAP failure. After failure, 25% (OR 0.33) of the newborns receiving nasal CPAP and 12.5% (OR 0.14) receiving NIPPV required invasive mechanical ventilation. Ventilatory support failure was significantly more frequent when nasal CPAP was used. Copyright © 2015 by Daedalus Enterprises.

Nasal continuous positive airways pressure immediately after extubation for preventing morbidity in preterm infants.

Science.gov (United States)

Davis, P G; Henderson-Smart, D J

2003-01-01

Preterm infants being extubated following a period of intermittent positive pressure ventilation via an endotracheal tube are at risk of developing respiratory failure as a result of apnea, respiratory acidosis and hypoxia. Nasal continuous positive airway pressure appears to stabilise the upper airway, improve lung function and reduce apnea and may therefore have a role in facilitating extubation in this population. In preterm infants having their endotracheal tube removed following a period of intermittent positive pressure ventilation (IPPV), does management with nasal continuous positive airways pressure (NCPAP) lead to an increased proportion remaining free of additional ventilatory support, compared to extubation directly to headbox oxygen? Searches were made of the Oxford Database of Perinatal Trials, MEDLINE up to November 2002, Cochrane Controlled Trials Register (The Cochrane Library, Issue 4, 2002), previous reviews including cross references, abstracts of conferences and symposia proceedings, expert informants and journal handsearching mainly in the English language. All trials utilising random or quasi-random patient allocation, in which NCPAP (delivered by any method) was compared with headbox oxygen for post-extubation care were included. Methodological quality was assessed independently by the two authors. Data were extracted independently by the two authors. Prespecified subgroup analysis to determine the impact of different levels of NCPAP, differences in duration of IPPV and use of aminophylline were also performed using the same package. Data were analysed using relative risk (RR), risk difference (RD) and number needed to treat (NNT). Nasal CPAP, when applied to preterm infants being extubated following IPPV, reduces the incidence of adverse clinical events (apnea, respiratory acidosis and increased oxygen requirements) indicating the need for additional ventilatory support [RR 0.62 (0.49, 0.77), RD -0.17 (-0.24,-0.10), NNT 6 (4,10)]. nasal

Estimation of the 3D positioning of anatomic structures from radiographic projection and volume knowledge

Energy Technology Data Exchange (ETDEWEB)

Bifulco, P; Cesarelli, M; Roccasalva Firenze, M; Verso, E; Sansone, M; Bracale, M [University of Naples, Federico II, Electronic Engineering Department, Bioengineering Unit, Via Claudio, 21 - 80125 Naples (Italy)

1999-12-31

The aim of this study is to develop a method to estimate the 3D positioning of an anatomic structure using the knowledge of its volume (provided by CT or MRI) combined with a single radiographic projection. This method could be applied in stereotactic surgery or in the study of 3D body joints kinematics. The knowledge of the 3D anatomical structure, available from CT (or in future MRI) is used to estimate the orientation of the projection that better match the actual 2D available projection. For this purpose it was necessary to develop an algorithm to simulate the radiographic projections. The radiographic image formation process has been simulated utilizing the geometrical characteristics of a real radiographic device and the volumetric anatomical data of the patient, obtained by 3D diagnostic CT images. The position of the patient volume respect to the radiological device is estimated comparing the actual radiographic projection with those simulated, maximising a similarity index. To assess the estimation, the 3D positioning of a segmented vertebra has been used as a test volume. The assessment has been carried out only by means of simulation. Estimation errors have been statistically evaluated. Conditions of mispositioning and noise have been also considered. The results relative to the simulation show the feasibility of the method. From the analysis of the errors emerges that the searching procedure results robust respect to the addition of white Gaussian noise. (authors) 13 fers., 4 figs., 1 tabs.

Estimation of the 3D positioning of anatomic structures from radiographic projection and volume knowledge

International Nuclear Information System (INIS)

Bifulco, P.; Cesarelli, M.; Roccasalva Firenze, M.; Verso, E.; Sansone, M.; Bracale, M.

1998-01-01

The aim of this study is to develop a method to estimate the 3D positioning of an anatomic structure using the knowledge of its volume (provided by CT or MRI) combined with a single radiographic projection. This method could be applied in stereotactic surgery or in the study of 3D body joints kinematics. The knowledge of the 3D anatomical structure, available from CT (or in future MRI) is used to estimate the orientation of the projection that better match the actual 2D available projection. For this purpose it was necessary to develop an algorithm to simulate the radiographic projections. The radiographic image formation process has been simulated utilizing the geometrical characteristics of a real radiographic device and the volumetric anatomical data of the patient, obtained by 3D diagnostic CT images. The position of the patient volume respect to the radiological device is estimated comparing the actual radiographic projection with those simulated, maximising a similarity index. To assess the estimation, the 3D positioning of a segmented vertebra has been used as a test volume. The assessment has been carried out only by means of simulation. Estimation errors have been statistically evaluated. Conditions of mispositioning and noise have been also considered. The results relative to the simulation show the feasibility of the method. From the analysis of the errors emerges that the searching procedure results robust respect to the addition of white Gaussian noise. (authors)

Flow and volume dependence of rat airway resistance during constant flow inflation and deflation.

Science.gov (United States)

Rubini, Alessandro; Carniel, Emanuele Luigi; Parmagnani, Andrea; Natali, Arturo Nicola

2011-12-01

The aim of this study was to measure the flow and volume dependence of both the ohmic and the viscoelastic pressure dissipations of the normal rat respiratory system separately during inflation and deflation. The study was conducted in the Respiratory Physiology Laboratory in our institution. Measurements were obtained for Seven albino Wistar rats of both sexes by using the flow interruption method during constant flow inflations and deflations. Measurements included anesthesia induction, tracheostomy and positioning of a tracheal cannula, positive pressure ventilation, constant flow respiratory system inflations and deflations at two different volumes and flows. The ohmic resistance exhibited volume and flow dependence, decreasing with lung volume and increasing with flow rate, during both inflation and deflation. The stress relaxation-related viscoelastic resistance also exhibited volume and flow dependence. It decreased with the flow rate at a constant lung volume during both inflation and deflation, but exhibited a different behavior with the lung volume at a constant flow rate (i.e., increased during inflations and decreased during deflations). Thus, stress relaxation in the rat lungs exhibited a hysteretic behavior. The observed flow and volume dependence of respiratory system resistance may be predicted by an equation derived from a model of the respiratory system that consists of two distinct compartments. The equation agrees well with the experimental data and indicates that the loading time is the critical parameter on which stress relaxation depends, during both lung inflation and deflation.

A direct method for determining complete positive and negative capillary pressure curves for reservoir rock using the centrifuge

Energy Technology Data Exchange (ETDEWEB)

Spinler, E.A.; Baldwin, B.A. [Phillips Petroleum Co., Bartlesville, OK (United States)

1997-08-01

A method is being developed for direct experimental determination of capillary pressure curves from saturation distributions produced during centrifuging fluids in a rock plug. A free water level is positioned along the length of the plugs to enable simultaneous determination of both positive and negative capillary pressures. Octadecane as the oil phase is solidified by temperature reduction while centrifuging to prevent fluid redistribution upon removal from the centrifuge. The water saturation is then measured via magnetic resonance imaging. The saturation profile within the plug and the calculation of pressures for each point of the saturation profile allows for a complete capillary pressure curve to be determined from one experiment. Centrifuging under oil with a free water level into a 100 percent water saturated plug results in the development of a primary drainage capillary pressure curve. Centrifuging similarly at an initial water saturation in the plug results in the development of an imbibition capillary pressure curve. Examples of these measurements are presented for Berea sandstone and chalk rocks.

THE ACHIEVABILITY OF TARGET CONVECTION VOLUMES IN ON-LINE HEMODIAFILTRATION

Directory of Open Access Journals (Sweden)

A. B. Sabodash

2015-01-01

Full Text Available Aim. To evaluate the achievability of recommended convection volumes in hemodiafiltration (HDF and impeding factors. Materials and methods. In short interventional one-center study among 67 stable prevalent dialysis patients we succeeded in achieving convection volume of more than 24 l/session in 60 patients (90%. Results. Substitution volume rose in the whole group from 21.1 ± 1.6 to 23.8 ± 1.2 l/session (p < 0.01. 12 patients, who didn`t achieve target volume had similar age, duration of renal replacement therapy and ultrafiltration rate as those who did. They differed from 55 patients who achieved target volume by substitution volume at first session in evaluation period (22.2 ± 1.7 vs. 23.6 ± 1.5 liters, р = 0.004, by transmembrane pressure (170 ± 40 vs. 146 ± 24 mmHg, р = 0.009 and by session duration (248 ± 15 vs. 262 ± 17 min, р = 0.0017. Blood flow rate also differed at the start of the study between the achievers and non-achievers: 353 ± 21 vs. 339 ± 19 ml/min, р = 0.035. The pressure in venous segment was lower in the achievers (154 ± 25 vs. 176 ± 36, р = 0.02 as well as transmembrane pressure (144 ± 24 vs. 164 ± 36, р = 0.014 which has been rising session by session in nonachievers. In non-achievers the membrane surface area was lower: 1.75 ± 0.2 vs. 1.91 ± 0.2 m2 (p = 0.02. In the multiple binary logistic regression model the session duration and membrane surface area were positive factors while the transmembrane pressure was negative one. Session prolonged by 15 min was associated with increase in relative chance to achieve target volume by 39% (95% CI 5–82%; р = 0.02. The membrane surface area enlarged by 0.1 m2 was linked with increase of chance by 4.2% (95% CI 0.2–8.4%; р = 0.04. The transmembrane pressure increased by 10 mmHg was associated with decreased chance to achieve target volume by 17% (95% CI 0–70%; р = 0.05. Conclusion. To achieve convection volume of 24 l/session one needs to afford

Control volume based hydrocephalus research; analysis of human data

Science.gov (United States)

Cohen, Benjamin; Wei, Timothy; Voorhees, Abram; Madsen, Joseph; Anor, Tomer

2010-11-01

Hydrocephalus is a neuropathophysiological disorder primarily diagnosed by increased cerebrospinal fluid volume and pressure within the brain. To date, utilization of clinical measurements have been limited to understanding of the relative amplitude and timing of flow, volume and pressure waveforms; qualitative approaches without a clear framework for meaningful quantitative comparison. Pressure volume models and electric circuit analogs enforce volume conservation principles in terms of pressure. Control volume analysis, through the integral mass and momentum conservation equations, ensures that pressure and volume are accounted for using first principles fluid physics. This approach is able to directly incorporate the diverse measurements obtained by clinicians into a simple, direct and robust mechanics based framework. Clinical data obtained for analysis are discussed along with data processing techniques used to extract terms in the conservation equation. Control volume analysis provides a non-invasive, physics-based approach to extracting pressure information from magnetic resonance velocity data that cannot be measured directly by pressure instrumentation.

Volume and leak measurements during neonatal CPAP in neonates

OpenAIRE

Fischer, Hendrik S.

2011-01-01

As yet, little is known about the effects of air leakages during CPAP in newborns. The present doctoral dissertation investigates tidal volume and leak measurements during nasal continuous positive airway pressure in neonates using a commercial ventilatory device. Investigations include in vitro studies, modelling and computer simulation as well as a clinical randomized cross-over trial in neonates.

Impact of ultrasound probe pressure on uterine positional displacement in gynecologic cancer patients

DEFF Research Database (Denmark)

Baker, Mariwan; Juhler-Nøttrup, Trine; Behrens, Claus F.

2014-01-01

Aim: The aim of this study was to quantify the uterine positional displacement induced by ultrasound probe pressure on a phantom and address the daily uterine motion in a healthy volunteer. Materials & methods: The phantom mimics the female pelvic region. The incorporated organs were subjected to...

Stability of the geometrically frustrated magnetic state of Ca3CoRhO6 to applications of positive and negative pressure

International Nuclear Information System (INIS)

Mohapatra, Niharika; Iyer, Kartik K; Jammalamadaka, S Narayana; Sampathkumaran, E V; Rayaprol, Sudhindra

2008-01-01

The influence of negative chemical pressure induced by gradual replacement of Ca by Sr as well as of external pressure (up to 10 kbar) on the magnetism of Ca 3 CoRhO 6 has been investigated by magnetization studies. It is found that the solid solution, Ca 3-x Sr x CoRhO 6 , exists at least until about x = 1.0 without any change in the crystal structure. Apart from insensitivity of the spin-chain feature to volume expansion, the characteristic features of geometrical frustration interestingly appear at the same temperatures for all compositions, in sharp contrast to the response to Y substitution for Ca (reported previously). Interestingly, the huge frequency dependence of ac susceptibility known for the parent compound persists for all compositions. We do not find a change in the properties under external pressure. The stability of the magnetic anomalies of this compound to volume change (about 4%) is puzzling

Expansion of the cathode spot and generation of shock waves in the plasma of a volume discharge in atmospheric-pressure helium

International Nuclear Information System (INIS)

Omarov, O. A.; Kurbanismailov, V. S.; Arslanbekov, M. A.; Gadzhiev, M. Kh.; Ragimkhanov, G. B.; Al-Shatravi, Ali J. G.

2012-01-01

The expansion of the cathode spot and the generation of shock waves during the formation and development of a pulsed volume discharge in atmospheric-pressure helium were studied by analyzing the emission spectra of the cathode plasma and the spatiotemporal behavior of the plasma glow. The transition of a diffuse volume discharge in a centimeter-long gap into a high-current diffuse mode when the gas pressure increased from 1 to 5 atm and the applied voltage rose from the statistical breakdown voltage to a 100% overvoltage was investigated. Analytical expressions for the radius of the cathode spot and its expansion velocity obtained in the framework of a spherically symmetric model agree satisfactorily with the experimental data.

Effect of Pneumoperitoneum and Lateral Position on Oropharyngeal Seal Pressures of Proseal LMA in Laparoscopic Urological Procedures.

Science.gov (United States)

Rustagi, Preeti; Patkar, Geeta A; Ourasang, Anil Kumar; Tendolkar, Bharati A

2017-02-01

A sustained and effective oropharyngeal sealing with supraglottic airway is required to maintain the ventilation during laparoscopic surgery. Previous studies have observed the Oropharyngeal Seal Pressure (OSP) for Proseal Laryngeal Mask Airway (PLMA) after pneumoperitoneum in supine and trendelenburg position, where PLMA was found to be an effective airway device. This study was conducted with ProSeal LMA, for laparoscopic Urologic procedures done in lateral position. To measure OSP in supine and lateral position and to observe the effect of pneumoperitoneum in lateral position on OSP. Secondary objectives were to assess adequacy of ventilation and incidence of adverse events. A total number of 25 patients of American Society of Anaesthesiologists (ASA) physical status II and I were enrolled. After induction of anaesthesia using a standardized protocol, PLMA was inserted. Ryle's tube was inserted through drain tube. The position of PLMA was confirmed with ease of insertion of Ryle's tube and fibreoptic grading of vocal cords. Patients were then put in lateral position. The OSP was measured in supine position. This value was baseline comparison for OSP in lateral position and that after pneumoperitoneum. We assessed the efficacy of PLMA for ventilation, after carboperitoneum in lateral position (peak airway pressure, End Tidal Carbon dioxide (EtCO 2 ), SPO 2 ). Incidence of adverse effects (displacement of device, gastric insufflation, regurgitation, coughing, sore throat, blood on device, trauma) was also noted. The OSP was above Peak Airway Pressure (PAP) in supine (22.1±5.4 and 15.4±4.49cm of H 2 O) and lateral position (22.6±5.3 and 16.1±4.6). After pneumoperitoneum, which was in lateral position, there was statistically significant (p-value <0.05) increase in both PAP (19.96±4.015) and OSP (24.32±4.98, p-value 0.03). There was no intraoperative displacement of PLMA. There was no event of suboptimal oxygenation. EtCO 2 was always within normal limits

Changes of ampulla pressure in the semicircular canal of pigeons by caloric stimulation

Science.gov (United States)

Wada, Yoshiro; Suzuki, Hiroyuki; Watanabe, Satoru

Still now several hypotheses about the mechanisms of the caloric nystagmus have been in conclusive. In this study we confirmed the convection effect and the volume change effect of the endolymph in horizontal semicircular canal following the caloric stimulation using pigeons ( Columba livia). Although the direction of the caloric nystagmus depended on the head position and the stimulus site of calorization, the caloric nystagmus disappeared after plugging of horizontal semicircular canal. On the other hand, the ampulla pressure increased by cold calorization and decreased by hot calorization and these pressure changes had no relation to the head position. These results show that the main role of the mechanisms of the caloric nystagmus under 1G is the convection effect but the volume change effect may act on the caloric nystagmus not only under 1G but also under microgravity.

Positive end expiratory pressure during one-lung ventilation: Selecting ideal patients and ventilator settings with the aim of improving arterial oxygenation

Directory of Open Access Journals (Sweden)

Hoftman Nir

2011-01-01

Full Text Available The efficacy of positive end-expiratory pressure (PEEP in treating intraoperative hypoxemia during one-lung ventilation (OLV remains in question given conflicting results of prior studies. This study aims to (1 evaluate the efficacy of PEEP during OLV, (2 assess the utility of preoperative predictors of response to PEEP, and (3 explore optimal intraoperative settings that would maximize the effects of PEEP on oxygenation. Forty-one thoracic surgery patients from a single tertiary care university center were prospectively enrolled in this observational study. After induction of general anesthesia, a double-lumen endotracheal tube was fiberoptically positioned and OLV initiated. Intraoperatively, PEEP = 5 and 10 cmH 2 O were sequentially applied to the ventilated lung during OLV. Arterial oxygenation, cardiovascular performance parameters, and proposed perioperative variables that could predict or enhance response to PEEP were analysed. T-test and c2 tests were utilized for continuous and categorical variables, respectively. Multivariate analyses were carried out using a classification tree model of binary recursive partitioning. PEEP improved arterial oxygenation by ≥20% in 29% of patients (n = 12 and failed to do so in 71% (n = 29; however, no cardiovascular impact was noted. Among the proposed clinical predictors, only intraoperative tidal volume per kilogram differed significantly between responders to PEEP and non-responders (mean 6.6 vs. 5.7 ml/kg, P = 0.013; no preoperative variable predicted response to PEEP. A multivariate analysis did not yield a clinically significant model for predicting PEEP responsiveness. PEEP improved oxygenation in a subset of patients; larger, although still protective tidal volumes favored a positive response to PEEP. No preoperative variables, however, could be identified as reliable predictors for PEEP responders.

ANALISIS SEGMENTASI, TARGETING, POSITIONING (STP TERHADAP PENINGKATAN VOLUME PENJUALAN PADA RUMAH GRIYA MULYA ASRI DI KOTA MAKASSAR

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Fitri _

2017-08-01

Full Text Available Volume at Griya Mulya Asri House In Makassar City. Guided by DR.Hj.Herminawati Abubakar., S.E., M.M and DR.Haeruddin Saleh., S.E., M.SiHome is a basic human need other than clothing and food. The increasing housing demand for Makassar residents encourages housing developers to provide more viable alternative housing solutions. Griya Mulya Asri Housing Estate is one of the best alternative choice for people who want a relaxed atmosphere amidst the urban bustle. Griya Mulya Asri Housing is very good for the habitable area in terms of price, facilities, comfort and location.This study aims to analyze the strategy of segmentation, targeting, positioning (STP applied by PT Hinda Assalam Brother to increase the sales volume of the house at Griya Mulya Asri. Analyzer used is multiple linear regression. Respondents of this research are Griya Mulya Asri resident. The result of analysis shows that segmentation, targeting, positioning strategy influence to the increase of sales volume.

Use of an iPad App to simulate pressure-volume loops and cardiovascular physiology.

Science.gov (United States)

Leisman, Staci; Burkhoff, Daniel

2017-09-01

The purpose of this laboratory exercise is to model the changes in preload, afterload, and contractility on a simulated pressure-volume loop and to correlate those findings with common measurements of clinical cardiovascular physiology. Once students have modeled these changes on a healthy heart, the students are asked to look at a simulated case of cardiogenic shock. Effects on preload, contractility, and afterload are explored, as well as the hemodynamic effects of a number of student-suggested treatment strategies. Copyright © 2017 the American Physiological Society.

Echocardiographic assessment of systolic pulmonary arterial pressure in HIV-positive patients.

Directory of Open Access Journals (Sweden)

Mehrnaz Rasoulinejad

2014-11-01

Full Text Available Pulmonary hypertension is rare but is one of the complications that occur due to HIV infection. Symptoms of HIV-associated pulmonary arterial hypertension are often non-specific but the main symptom of the disease is dyspnea. In this cross-sectional study, we measured systolic pulmonary arterial pressure (SPAP by echocardiographic methods among HIV-positive patients who received ART. This research is a descriptive, cross-sectional study of 170 HIV-positive patients that was conducted in Imam-Khomeini hospital, Tehran, Iran during 2011-2013. All patients regularly received antiretroviral therapy at least for recent 2 years. There were not any cardiopulmonary symptoms (cough, dyspnea, exertional fatigue and chest discomfort in these patients. All participants underwent echocardiography to estimate SPAP. The participants comprised 108 males (63.5% and 62 females (46.5%. The mean age of patients was 41 years old, and the mean duration of HIV infection was 5.5 years. The mean CD4 cell count was 401 cell/µl. The principal regimen of antiretroviral therapy included two nucleoside reverse transcriptase inhibitor (NRTI and one non-nucleoside reverse transcriptase inhibitor (NNRTI in the hospital. The mean of systolic pulmonary arterial pressure was 25 mmHg in the participants; 156 (93.4% of them had SPAP ≤ 30 mmHg (normal, six (3.6% had SPAP: 31-35 mmHg (borderline and five (3% had SPAP > 35 mmHg (pulmonary hypertension. Our results indicated a significant increase of pulmonary hypertension in asymptomatic HIV-positive patients that had no association with any other risk factor. Also, antiretroviral therapy was not a risk factor for pulmonary hypertension in this study.

[Comparison of different continuous positive airway pressure titration methods for obstructive sleep apnea hypopnea syndrome].

Science.gov (United States)

Li, Jingjing; Ye, Jingying; Zhang, Peng; Kang, Dan; Cao, Xin; Zhang, Yuhuan; Ding, Xiu; Zheng, Li; Li, Hongguang; Bian, Qiuli

2014-10-01

To explore whether there were differences between the results of automatic titration and the results of manual titration for positive airway pressure treatment in patients with obstructive sleep apnea hypopnea syndrome (OSAHS) and its influencing factors, the results might provide a theoretical basis for the rational use of two pressure titration methods. Sixty one patients with OSAHS were included in this study. All patients underwent a manual titration and an automatic titration within one week. The clinical informations, polysomnography data, and the results of both two titration of all patients were obtained for analysis. The overall apnea/hypopnea index was (63.1 ± 17.7)/h, with a range of 14.9/h to 110.4/h. The treatment pressure of manual titration was (8.4 ± 2.1) cmH(2)O, which was significantly lower than the treatment pressure of automatic titration, (11.5 ± 2.7) cmH(2)O (t = -9.797, P titration and manual titration), it was found that the pressure of automatic titration was significantly higher in patients with a ΔP > 3 cmH(2)O than in patients with a ΔP ≤ 3 cmH(2)O, which was (13.3 ± 2.3) cmH(2)O vs (10.0 ± 2.0) cmH(2)O (t = -6.159, P titration between these two groups, which was (8.6 ± 2.4) cmH(2)O vs (8.3 ± 2.0)cmH(2)O (P > 0.05). There was no significant difference in age, body mass index, neck circumference, abdomen circumference, apnea hypopnea index, and arterial oxygen saturation between these two groups. The treatment pressure of automatic titration is usually higher than that of manual titration. For patients with a high treatment pressure which is derived from automatic titration, a suggestion about manual titration could be given to decrease the potential treatment pressure of continuous positive airway pressure, which may be helpful in improving the comfortableness and the compliance of this treatment.

Noninvasive pulse pressure variation and stroke volume variation to predict fluid responsiveness at multiple thresholds : a prospective observational study

NARCIS (Netherlands)

Vos, Jaap Jan; Poterman, Marieke; Papineau Salm, Pieternel; Van Amsterdam, Kai; Struys, Michel M. R. F.; Scheeren, Thomas W. L.; Kalmar, Alain F.

2015-01-01

Pulse pressure variation (PPV) and stroke volume variation (SVV) are dynamic preload variables that can be measured noninvasively to assess fluid responsiveness (FR) in anesthetized patients with mechanical ventilation. Few studies have examined the effectiveness of predicting FR according to the

Estimation of lung volume and pressure from electrocardiogram

KAUST Repository

Elsayed, Gamal Eldin Fathy Amin

2011-05-01

The Electrocardiography (ECG) is a tool measuring the electrical excitation of the heart that is extensively used for diagnosis and monitoring of heart diseases. The ECG signal reflects not only the heart activity but also many other physiological processes. The respiratory activity is a prominent process that affects the ECG signal due to the close proximity of the heart and the lungs and, on the other hand, due to neural regulatory processes. In this paper, several means for the estimation of the respiratory process from the ECG signal are presented. The results show a strong correlation of the voltage difference between the R and S peak of the ECG and the lung\\'s volume and pressure. Correlation was also found for some features of the vector ECG, which is a two dimensional graph of two different ECG signals. The potential benefit of the multiparametric evaluation of the ECG signal is a reduction of the number of sensors connected to patients, which will increase the patients\\' comfort and reduce the costs associated with healthcare. In particular, it is relevant for sleep monitoring, where a reduction of the number of different sensors would facilitate a more natural sleeping environment and hence a higher sensitivity of the diagnosis. © 2011 IEEE.

Work of breathing using different interfaces in spontaneous positive pressure ventilation: helmet, face-mask, and endotracheal tube.

Science.gov (United States)

Oda, Shinya; Otaki, Kei; Yashima, Nozomi; Kurota, Misato; Matsushita, Sachiko; Kumasaka, Airi; Kurihara, Hutaba; Kawamae, Kaneyuki

2016-08-01

Noninvasive positive pressure ventilation (NPPV) using a helmet is expected to cause inspiratory trigger delay due to the large collapsible and compliant chamber. We compared the work of breathing (WOB) of NPPV using a helmet or a full face-mask with that of invasive ventilation by tracheal intubation. We used a lung model capable of simulating spontaneous breathing (LUNGOO; Air Water Inc., Japan). LUNGOO was set at compliance (C) = 50 mL/cmH2O and resistance (R) = 5 cmH2O/L/s for normal lung simulation, C = 20 mL/cmH2O and R = 5 cmH2O/L/s for restrictive lung, and C = 50 mL/cmH2O and R = 20 cmH2O/L/s for obstructive lung. Muscle pressure was fixed at 25 cmH2O and respiratory rate at 20 bpm. Pressure support ventilation and continuous positive airway pressure were performed with each interface placed on a dummy head made of reinforced plastic that was connected to LUNGOO. We tested the inspiratory WOB difference between the interfaces with various combinations of ventilator settings (positive end-expiratory pressure 5 cmH2O; pressure support 0, 5, and 10 cmH2O). In the normal lung and restrictive lung models, WOB decreased more with the face-mask than the helmet, especially when accompanied by the level of pressure support. In the obstructive lung model, WOB with the helmet decreased compared with the other two interfaces. In the mixed lung model, there were no significant differences in WOB between the three interfaces. NPPV using a helmet is more effective than the other interfaces for WOB in obstructive lung disease.

Control of positive end-expiratory pressure (PEEP for small animal ventilators

Directory of Open Access Journals (Sweden)

Leão Nunes Marcelo V

2010-07-01

Full Text Available Abstract Background The positive end-expiratory pressure (PEEP for the mechanical ventilation of small animals is frequently obtained with water seals or by using ventilators developed for human use. An alternative mechanism is the use of an on-off expiratory valve closing at the moment when the alveolar pressure is equal to the target PEEP. In this paper, a novel PEEP controller (PEEP-new and the PEEP system of a commercial small-animal ventilator, both based on switching an on-off valve, are evaluated. Methods The proposed PEEP controller is a discrete integrator monitoring the error between the target PEEP and the airways opening pressure prior to the onset of an inspiratory cycle. In vitro as well as in vivo experiments with rats were carried out and the PEEP accuracy, settling time and under/overshoot were considered as a measure of performance. Results The commercial PEEP controller did not pass the tests since it ignores the airways resistive pressure drop, resulting in a PEEP 5 cmH2O greater than the target in most conditions. The PEEP-new presented steady-state errors smaller than 0.5 cmH2O, with settling times below 10 s and under/overshoot smaller than 2 cmH2O. Conclusion The PEEP-new presented acceptable performance, considering accuracy and temporal response. This novel PEEP generator may prove useful in many applications for small animal ventilators.

Detecting Output Pressure Change of Positive-Displacement Pump by Phase Trajectory Method

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Jerzy Stojek

2010-06-01

Full Text Available The monitoring of hydraulic system condition change during its exploitation ran its complex problem. The main task is to identifyearly phase damage of hydraulic system elements (pumps, valves, ect. in order to take decision which can avoid hydraulic system breakdown. This paper presents the possibility of phase trajectories use in detecting output pressure change of hydraulic system causedby positive-displacement pump wear.

The impact of arm position and pulse pressure on the validation of a wrist-cuff blood pressure measurement device in a high risk population

Directory of Open Access Journals (Sweden)

Ali Reza Khoshdel

2010-03-01

Full Text Available Ali Reza Khoshdel1,2, Shane Carney2, Alastair Gillies21Faculty of Medicine, Aja University of Medical Science, Tehran, Iran; 2John Hunter Hospital, Faculty of Health, The University of Newcastle, Newcastle, NS W, AustraliaAbstract: Despite the increasing popularity of blood pressure (BP wrist monitors for self-BP measurement at home, device validation and the effect of arm position remains an issue. This study focused on the validation of the Omron HEM-609 wrist BP device, including an evaluation of the impact of arm position and pulse pressure on BP measurement validation. Fifty patients at high risk for cardiovascular disease were selected (age 65 ± 10 years. Each patient had two measurements with a mercury sphygmomanometer and three measurements with the wrist BP device (wrist at the heart level while the horizontal arm supported [HORIZONTAL], hand supported on the opposite shoulder [SHOULDER], and elbow placed on a desk [DESK], in random order. The achieved systolic BP (SBP and diastolic BP (DBP wrist-cuff readings were compared to the mercury device and the frequencies of the readings within 5, 10, and 15 mmHg of the gold standard were computed and compared with the British Hypertension Society (BHS and Association for the Advancement of Medical Instrumentation (AAMI protocols. The results showed while SBP readings with HORIZONTAL and SHOULDER positions were significantly different from the mercury device (mean difference = 7.1 and 13.3 mmHg, respectively; P < 0.05, the DESK position created the closest reading to mercury (mean difference = 3.8, P > 0.1. Approximately 71% of SBP readings with the DESK position were within ±10 mmHg, whereas it was 62.5% and 34% for HORIZONTAL and SHOULDER positions, respectively. Wrist DBP attained category D with BHS criteria with all three arm positions. Bland–Altman plots illustrated that the wrist monitor systematically underestimated SBP and DBP values. However a reading adjustment of 5 and 10 mm

Device for positioning ultrasonic probes and/or television cameras on the outer surface of reactor pressure vessels

International Nuclear Information System (INIS)

Zipser, R.; Dose, G.F.

1977-01-01

The device makes possible periodical in-service inspections of welding seams and material of a reactor pressure vessel without local human presence. A 'support ring' encloses the pressure vessel in a horizontal plane with free space. It is vertically moved up and down in the space between pressure vessel and thermal shield by means of tackles. At a control desk placed in a protected area its movement is controlled and its vertical position is indicated. A 'rotating track' with its own drive is rotating remote-controlled on the 'support ring'. By a combination of the vertical with the rotating movement, an ultrasonic probe placed removably on the 'rotating hack', or a television camera will be brought to any position on the cylindrical circumference of the pressure vessel. Special devices extend the radius of action, in upward direction for inspecting the welding seams of the coolant nozzles, and in downward direction for the inspection of welds on the hemispherical bottom of the pressure vessel or on the outlet pipe nozzle placed there. The device remains installed during reactor operation, but is moved down to the lower horizontal surface of the thermal shield. Parts which are sensible to radiation like probes or television cameras and special devices will then be removed respectively mounted before beginning an inspection compaign. This position may be reached by the lower access in the biological shield and through an opening in the horizontal surface of the thermal shield. (HP) [de

Spontaneous breathing during lung-protective ventilation in an experimental acute lung injury model: high transpulmonary pressure associated with strong spontaneous breathing effort may worsen lung injury.

Science.gov (United States)

Yoshida, Takeshi; Uchiyama, Akinori; Matsuura, Nariaki; Mashimo, Takashi; Fujino, Yuji

2012-05-01

We investigated whether potentially injurious transpulmonary pressure could be generated by strong spontaneous breathing and exacerbate lung injury even when plateau pressure is limited to ventilation, each combined with weak or strong spontaneous breathing effort. Inspiratory pressure for low tidal volume ventilation was set at 10 cm H2O and tidal volume at 6 mL/kg. For moderate tidal volume ventilation, the values were 20 cm H2O and 7-9 mL/kg. The groups were: low tidal volume ventilation+spontaneous breathingweak, low tidal volume ventilation+spontaneous breathingstrong, moderate tidal volume ventilation+spontaneous breathingweak, and moderate tidal volume ventilation+spontaneous breathingstrong. Each group had the same settings for positive end-expiratory pressure of 8 cm H2O. Respiratory variables were measured every 60 mins. Distribution of lung aeration and alveolar collapse were histologically evaluated. Low tidal volume ventilation+spontaneous breathingstrong showed the most favorable oxygenation and compliance of respiratory system, and the best lung aeration. By contrast, in moderate tidal volume ventilation+spontaneous breathingstrong, the greatest atelectasis with numerous neutrophils was observed. While we applied settings to maintain plateau pressure at ventilation+spontaneous breathingstrong, transpulmonary pressure rose >33 cm H2O. Both minute ventilation and respiratory rate were higher in the strong spontaneous breathing groups. Even when plateau pressure is limited to mechanical ventilation, transpulmonary pressure and tidal volume should be strictly controlled to prevent further lung injury.

Is aerobic workload positively related to ambulatory blood pressure?

DEFF Research Database (Denmark)

Korshøj, Mette; Clays, Els; Lidegaard, Mark

2016-01-01

workload and ambulatory blood pressure (ABP) are lacking. The aim was to explore the relationship between objectively measured relative aerobic workload and ABP. METHODS: A total of 116 cleaners aged 18-65 years were included after informed consent was obtained. A portable device (Spacelabs 90217......) was mounted for 24-h measurements of ABP, and an Actiheart was mounted for 24-h heart rate measurements to calculate relative aerobic workload as percentage of relative heart rate reserve. A repeated-measure multi-adjusted mixed model was applied for analysis. RESULTS: A fully adjusted mixed model...... of measurements throughout the day showed significant positive relations (p ABP and 0.30 ± 0.04 mmHg (95 % CI 0.22-0.38 mmHg) in diastolic ABP. Correlations between...

The volume dependence of thermal pressure in perovskite and other minerals

Science.gov (United States)

Anderson, Orson L.

1999-04-01

This is a review paper concerning the thermal pressure, PTH, of solids and the conditions under which it is independent of volume. When PTH is independent of V, the general equation of state (EoS) reduces from P(V,T)=P 1(V,0)+P TH(V,T) to P(V,T)=P 1(V,0)+P THV 0,T , and thus is separated into two independent mathematical functions. P1( V,0) is the isothermal EoS. Four tests of thermoelastic data are shown to determine the T and V range in which PTH is independent of volume. Eighteen solids are examined. Most of these are minerals, but two metals, three alkali metals and three noble gases are also included. The focus is on three lower mantle minerals, MgSiO 3, MgO, and CaSiO 3. For these three minerals (∂ PTH/∂ V) T vanishes at conditions of the lower mantle, but PTH is a function of V at ambient conditions. However, for most solids, (∂ PTH/∂ V) T becomes zero at high temperature. The behavior of (∂ PTH/∂ V) T is apparently not correlated with such properties as crystal class, chemical composition, bonding type, and anharmonicity. The vanishing of (∂ PTH/∂ V) T is strictly a high temperature property of solids.

Effect of volume loading on the Frank-Starling relation during reductions in central blood volume in heat-stressed humans

DEFF Research Database (Denmark)

Bundgaard-Nielsen, Morten; Wilson, T E; Seifert, Thomas

2010-01-01

During reductions in central blood volume while heat stressed, a greater decrease in stroke volume (SV) for a similar decrease in ventricular filling pressure, compared to normothermia, suggests that the heart is operating on a steeper portion of a Frank-Starling curve. If so, volume loading...... of heat-stressed individuals would shift the operating point to a flatter portion of the heat stress Frank-Starling curve thereby attenuating the reduction in SV during subsequent decreases in central blood volume. To investigate this hypothesis, right heart catheterization was performed in eight males...... from whom pulmonary capillary wedge pressure (PCWP), central venous pressure and SV (via thermodilution) were obtained while central blood volume was reduced via lower-body negative pressure (LBNP) during normothermia, whole-body heating (increase in blood temperature 1 degrees C), and during whole...

[Treatment of acute respiratory distress syndrome using pressure and volume controlled ventilation with lung protective strategy].

Science.gov (United States)

Ge, Ying; Wan, Yong; Wang, Da-qing; Su, Xiao-lin; Li, Jun-ying; Chen, Jing

2004-07-01

To investigate the significance and effect of pressure controlled ventilation (PCV) as well as volume controlled ventilation (VCV) by lung protective strategy on respiratory mechanics, blood gas analysis and hemodynamics in patients with acute respiratory distress syndrome (ARDS). Fifty patients with ARDS were randomly divided into PCV and VCV groups with permissive hypercapnia and open lung strategy. Changes in respiratory mechanics, blood gas analysis and hemodynamics were compared between two groups. Peak inspiration pressure (PIP) in PCV group was significantly lower than that in VCV group, while mean pressure of airway (MPaw) was significantly higher than that in VCV after 24 hours mechanical ventilation. After 24 hours mechanical ventilation, there were higher central venous pressure (CVP) and slower heart rate (HR) in two groups, CVP was significantly higher in VCV compared with PCV, and PCV group had slower HR than VCV group, the two groups had no differences in mean blood pressure (MBP) at various intervals. All patients showed no ventilator-induced lung injury. Arterial blood oxygenations were obviously improved in two groups after 24 hours mechanical ventilation, PCV group had better partial pressure of oxygen in artery (PaO2) than VCV group. Both PCV and VCV can improve arterial blood oxygenations, prevent ventilator-induced lung injury, and have less disturbance in hemodynamic parameters. PCV with lung protective ventilatory strategy should be early use for patients with ARDS.

Relationship between pre-extubation positive endexpiratory pressure and oxygenation after coronary artery bypass grafting

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Reijane Oliveira Lima

2015-08-01

Full Text Available Abstract Introduction After removal of endotracheal tube and artificial ventilation, ventilatory support should be continued, offering oxygen supply to ensure an arterial oxygen saturation close to physiological. Objective: The aim of this study was to investigate the effects of positive-end expiratory pressure before extubation on the oxygenation indices of patients undergoing coronary artery bypass grafting. Methods: A randomized clinical trial with seventy-eight patients undergoing coronary artery bypass grafting divided into three groups and ventilated with different positive-end expiratory pressure levels prior to extubation: Group A, 5 cmH2O (n=32; Group B, 8 cmH2O (n=26; and Group C, 10 cmH2O (n=20. Oxygenation index data were obtained from arterial blood gas samples collected at 1, 3, and 6 h after extubation. Patients with chronic pulmonary disease and those who underwent off-pump, emergency, or combined surgeries were excluded. For statistical analysis, we used Shapiro-Wilk, G, Kruskal-Wallis, and analysis of variance tests and set the level of significance at P<0.05. Results Groups were homogenous with regard to demographic, clinical, and surgical variables. There were no statistically significant differences between groups in the first 6 h after extubation with regard to oxygenation indices and oxygen therapy utilization. Conclusion: In this sample of patients undergoing coronary artery bypass grafting, the use of different positive-end expiratory pressure levels before extubation did not affect gas exchange or oxygen therapy utilization in the first 6 h after endotracheal tube removal.

Effects of body position and extension of the neck and extremities on lung volume measured via computed tomography in red-eared slider turtles (Trachemys scripta elegans).

Science.gov (United States)

Mans, Christoph; Drees, Randi; Sladky, Kurt K; Hatt, Jean-Michel; Kircher, Patrick R

2013-10-15

To determine the effects of body position and extension of the neck and extremities on CT measurements of ventilated lung volume in red-eared slider turtles (Trachemys scripta elegans). Prospective crossover-design study. 14 adult red-eared slider turtles. CT was performed on turtles in horizontal ventral recumbent and vertical left lateral recumbent, right lateral recumbent, and caudal recumbent body positions. In sedated turtles, evaluations were performed in horizontal ventral recumbent body position with and without extension of the neck and extremities. Lung volumes were estimated from helical CT images with commercial software. Effects of body position, extremity and neck extension, sedation, body weight, and sex on lung volume were analyzed. Mean ± SD volume of dependent lung tissue was significantly decreased in vertical left lateral (18.97 ± 14.65 mL), right lateral (24.59 ± 19.16 mL), and caudal (9.23 ± 12.13 mL) recumbent positions, compared with the same region for turtles in horizontal ventral recumbency (48.52 ± 20.08 mL, 50.66 ± 18.08 mL, and 31.95 ± 15.69 mL, respectively). Total lung volume did not differ among positions because of compensatory increases in nondependent lung tissue. Extension of the extremities and neck significantly increased total lung volume (127.94 ± 35.53 mL), compared with that in turtles with the head, neck, and extremities withdrawn into the shell (103.24 ± 40.13 mL). Vertical positioning of red-eared sliders significantly affected lung volumes and could potentially affect interpretation of radiographs obtained in these positions. Extension of the extremities and neck resulted in the greatest total lung volume.

[Reduction of pressure sores during prone positioning of ventilated intensive care patients by the prone-head support system: a pilot study].

Science.gov (United States)

Prebio, Michael; Katz-Papatheophilou, Elfriede; Heindl, Werner; Gelbmann, Herbert; Burghuber, Otto C

2005-02-01

Prone positioning in patients with adult respiratory distress syndrome is a well-known method to improve oxygenation. The aim of our study was to evaluate a new device for prone positioning, the prone-head support system (PHS system), with regard to reduction of cutaneous pressure sores. In a pilot study we randomized 8 patients with ARDS in two groups: 180 degrees standard prone positioning (group without mask) and prone positioning with the PHS system (group with mask). The PHS system consists of a facemask support, which is connected to an adapted air suspension bed. The patients of both groups were intermittently proned for several days. We evaluated the pressure sores on head and neck before turning the patients prone for the first time and after each period of prone positioning. We documented the quantity, the size, the type and the localization of the pressure sores. There was no significant difference in the mean duration of prone positioning (27.1+/-14.7 hours in the group with mask versus 24.5+/-18.7 h in the group without mask). In the group with mask there were 1.5+/-0.8 new pressure sores by each proning, whereas in the group without mask there were 2.37+/-1.6 new pressure sores, which was lower, but not significantly. The overall area of pressure sores (798 mm2 versus 3184 mm2, p=0.004), the area of pressure sores per patient (199.5+/-104.7 mm2 versus 796+/-478 mm2, p=0.03) and the increase of the area of pressure sores per proning (79.8+/-52.0 mm2 versus 398.0+/-214.3 mm2, p=0.004) were significantly lower in the group with mask in comparison to the group without mask. The lips were the most effected localization in both groups. The pressure sores in the group with mask were less severe and showed a homogenous distribution in comparison to the group without mask. Blisters dominated in the group with mask in comparison to erosions, necrosis and ulcers in the group without mask. The PHS system with its face mask is able to reduce the extent and the

Choking under Pressure: When an Additional Positive Stereotype Affects Performance for Domain Identified Male Mathematics Students

Science.gov (United States)

Rosenthal, Harriet E. S.; Crisp, Richard J.

2007-01-01

This research aimed to establish if the presentation of two positive stereotypes would result in choking under pressure for identified male mathematics students. Seventy-five 16 year old men, who had just commenced their AS-level study, were either made aware of their gender group membership (single positive stereotype), their school group…

Randomized trial of prongs or mask for nasal continuous positive airway pressure in preterm infants.

LENUS (Irish Health Repository)

Kieran, Emily A

2012-11-01

To determine whether nasal continuous positive airway pressure (NCPAP) given with nasal prongs compared with nasal mask reduces the rate of intubation and mechanical ventilation in preterm infants within 72 hours of starting therapy.

Reduced local immune response with continuous positive airway pressure during one-lung ventilation for oesophagectomy

NARCIS (Netherlands)

Verhage, R. J. J.; Boone, J.; Rijkers, G. T.; Cromheecke, G. J.; Kroese, A. C.; Weijs, T. J.; Borel Rinkes, I. H. M.; van Hillegersberg, R.

2014-01-01

Background. Transthoracic oesophagectomy requires prolonged one-lung ventilation causing systemic and local inflammatory responses. Application of continuous positive airway pressure (CPAP) to the collapsed lung potentially reduces pulmonary damage, hypoxia, and consequent inflammation. This

Effect of head rotation on cerebral blood velocity in the prone position

DEFF Research Database (Denmark)

Højlund, Jakob; Sandmand, Marie; Sonne, Morten

2012-01-01

for cerebral blood flow. We tested in healthy subjects the hypothesis that rotating the head in the prone position reduces cerebral blood flow. Methods. Mean arterial blood pressure (MAP), stroke volume (SV), and CO were determined, together with the middle cerebral artery mean blood velocity (MCA V...... V(mean) ~10% in spite of an elevated MAP. Prone positioning with rotated head affects both CBF and cerebrovenous drainage indicating that optimal brain perfusion requires head centering....

An analysis of system pressure and temperature distribution in self-pressurizer of SMART and calculation of sizing of wet thermal insulator and pressurizer cooler

Energy Technology Data Exchange (ETDEWEB)

Kang, Yeon Moon; Lee, Doo Jeong; Yoon, Ju Hyun; Kim, Hwan Yeol [Korea Atomic Energy Research Institute, Taejon (Korea)

1999-03-01

To evaluate the amount of heat transfer from coolant to gas in reactor vessel heat transfer through the structure of pressurizer and evaporation/condensation on surface of liquid pool should be considered. And, also the heat exchange by pressurizer cooler and heat transfer to upper plate of reactor vessel should be considered. Thus, overall examinations on design variables which affect the heat transfer from coolant to gas are needed to maintain the pressurizer conditions at designed value for normal operation through heatup process. The major design variables, which affect system pressure and gas temperature during heatup, and the sizes of wet thermal insulator and pressurizer cooler, and volume of gas cylinder connected to pressurizer. A computer program is developed for the prediction of system pressure and temperature of pressurizer gas region with considering volume expansion of coolant and heat transfer from coolant to gas during heatup. Using the program, this report suggests the optimized design values of wet thermal insulator, pressurizer cooler, and volume of gas cylinder to meet the target conditions for normal operation of SMART. (author). 6 refs., 17 figs., 5 tabs.

Stroke volume variation compared with pulse pressure variation and cardiac index changes for prediction of fluid responsiveness in mechanically ventilated patients

Directory of Open Access Journals (Sweden)

Randa Aly Soliman

2015-04-01

Conclusions: Baseline stroke volume variation ⩾8.15% predicted fluid responsiveness in mechanically ventilated patients with acute circulatory failure. The study also confirmed the ability of pulse pressure variation to predict fluid responsiveness.

A Computational Model of Hydraulic Volume Displacement Drive

Directory of Open Access Journals (Sweden)

V. N. Pil'gunov

2014-01-01

Full Text Available The paper offers a computational model of industrial-purpose hydraulic drive with two hydraulic volume adjustable working chamber machines (pump and motor. Adjustable pump equipped with the pressure control unit can be run together with several adjustable hydraulic motors on the principle of three-phase hydraulic socket-outlet with high-pressure lines, drain, and drainage system. The paper considers the pressure-controlled hydrostatic transmission with hydraulic motor as an output link. It shows a possibility to create a saving hydraulic drive using a functional tie between the adjusting parameters of the pump and hydraulic motor through the pressure difference, torque, and angular rate of the hydraulic motor shaft rotation. The programmable logic controller can implement such tie. The Coulomb and viscous frictions are taken into consideration when developing a computational model of the hydraulic volume displacement drive. Discharge balance considers external and internal leakages in equivalent clearances of hydraulic machines, as well as compression loss volume caused by hydraulic fluid compressibility and deformation of pipe walls. To correct dynamic properties of hydraulic drive, the paper offers that in discharge balance are included the additional regulated external leakages in the open circuit of hydraulic drive and regulated internal leakages in the closed-loop circuit. Generalized differential equations having functional multipliers and multilinked nature have been obtained to describe the operation of hydraulic positioning and speed drive with two hydraulic volume adjustable working chamber machines. It is shown that a proposed computational model of hydraulic drive can be taken into consideration in development of LS («Load-Sensing» drives, in which the pumping pressure is tuned to the value required for the most loaded slave motor to overcome the load. Results attained can be used both in designing the industrial-purpose heavy

A finite volume study for pressure waves propagation in a straight section of pipeline with caviation

Directory of Open Access Journals (Sweden)

C Silva

2016-09-01

Full Text Available The main objective of this research was to study the pressure waves propagation generated by a sudden closure of a valve in a straight pipe. The physical model consisted of a head tank that can be pressurized with air, and a copper pipe with a fast-closing ball valve on the downstream end of the line. The cavitation and fluid-structure interaction phenomena were integrated analytically into the one-dimensional continuity and momentum equations, by assuming that the fluid density and the flow area vary with pressure. These equations were solved through a high resolution finite volume method, in combination with others numerical methods such as Taylor series expansion, Newton method, Simpson's Rule and quadratic interpolation. Due to the complexity of the solution procedure, a computational code in FORTRAN 95 language was developed in order to obtain numerical solutions. Several discretizations of the computational grid were achieved to assess their impact on the solution. The model was validated with experimental data and analytic results obtained by other researchers. Several pressure values, in different points of pipe, were compared, and an excellent agreement was found for both cases.

Partial molar volumes of organic solutes in water. XXVII. Two aliphatic polyethers (triglyme, tetraglyme) at temperatures T = 298–573 K and pressures up to 30 MPa

International Nuclear Information System (INIS)

Cibulka, Ivan

2016-01-01

Highlights: • Standard molar volumes of two linear aliphatic polyethers in water are presented. • Data were obtained in the range T from (298 to 573) K and p up to 30 MPa. • Data combined with those obtained previously are analyzed and compared with standard molar volumes of cyclic ethers. - Abstract: Densities of dilute aqueous solutions of two linear aliphatic polyethers: 2,5,8,11-tetraoxadodecane (triethylene glycol dimethyl ether, triglyme) and 2,5,8,11,14-pentaoxapentadecane (tetraethylene glycol dimethyl ether, tetraglyme), measured in the temperature range from (298 to 573) K and at pressures up to 30 MPa using an automated flow vibrating-tube densimeter are reported. Standard molar volumes were evaluated from the measured data. The present values complement previous measurements performed for the title polyethers at atmospheric pressure in the temperature range from (278 to 343) K and extend the knowledge to temperature and pressure ranges in which the data on standard molar volumes for lower members of the homologous series (monoglyme, diglyme) are already available.

Densities and apparent molar volumes of HClO{sub 4}(aq) and Yb(ClO{sub 4}){sub 3}(aq) at elevated temperatures and pressures

Energy Technology Data Exchange (ETDEWEB)

Hakin, Andrew W. E-mail: hakin@uleth.ca; Lukacs, Michael J.; Jin Lianliu

2004-09-01

Relative densities have been measured for acidified aqueous solutions of ytterbium perchlorate {l_brace}Yb(ClO{sub 4}){sub 3}{r_brace} at approximately T=(348.15, 373.15, 398.15, and 423.15) K and p=(10.0, 20.0, and 30.0) MPa over the concentration range 0.01624{<=}m{sub 2}/(mol {center_dot} kg{sup -1}) {<=} 0.2531 using an optically coupled vibrating tube densimeter (OCVTD). Experimental apparent molar volumes have been calculated from the density measurements, and apparent molar volumes for the aqueous perchlorate salt have been calculated using Young's rule. The application of Young's rule requires apparent molar volumes for aqueous perchloric acid (HClO{sub 4}) solutions over extended temperature and pressure ranges. These values were calculated from densities for aqueous HClO{sub 4} solutions that were measured using the OCVTD at the same temperatures and pressures as those used to investigate the density surface of the acidified aqueous Yb(ClO{sub 4}){sub 3} solutions. The temperature, pressure, and composition surfaces of the apparent molar volumes for Yb(ClO{sub 4}){sub 3}(aq) and HClO{sub 4}(aq) have been modelled using Pitzer ion-interaction equations. Apparent molar volumes at infinite dilution obtained from these models have been compared to those which can be calculated using the semi-empirical Helgeson, Kirkham, and Flowers equations of state. Values for the apparent molar volume at infinite dilution of the ytterbium trivalent cation have also been calculated using simple additivity principles.

Alveolar Tidal recruitment/derecruitment and Overdistension During Four Levels of End-Expiratory Pressure with Protective Tidal Volume During Anesthesia in a Murine Lung-Healthy Model.

Science.gov (United States)

Soares, Joao Henrique Neves; Carvalho, Alysson Roncally; Bergamini, Bruno Curty; Gress, Maria Alice Kuster; Jandre, Frederico Caetano; Zin, Walter Araujo; Giannella-Neto, Antonio

2018-06-01

We compared respiratory mechanics between the positive end-expiratory pressure of minimal respiratory system elastance (PEEP minErs ) and three levels of PEEP during low-tidal-volume (6 mL/kg) ventilation in rats. Twenty-four rats were anesthetized, paralyzed, and mechanically ventilated. Airway pressure (P aw ), flow (F), and volume (V) were fitted by a linear single compartment model (LSCM) P aw (t) = E rs  × V(t) + R rs  × F(t) + PEEP or a volume- and flow-dependent SCM (VFDSCM) P aw (t) = (E 1  + E 2  × V(t)) × V(t) + (K 1  + K 2  × |F(t)|) × F(t) + PEEP, where E rs and R rs are respiratory system elastance and resistance, respectively; E 1 and E 2 × V are volume-independent and volume-dependent E rs , respectively; and K 1 and K 2  × F are flow-independent and flow-dependent R rs , respectively. Animals were ventilated for 1 h at PEEP 0 cmH 2 O (ZEEP); PEEP minErs ; 2 cmH 2 O above PEEP minErs (PEEP minErs+2 ); or 4 cmH 2 O above PEEP minErs (PEEP minErs+4 ). Alveolar tidal recruitment/derecruitment and overdistension were assessed by the index %E 2  = 100 × [(E 2  × V T )/(E 1  + |E 2 | × V T )], and alveolar stability by the slope of E rs (t). %E 2 varied between 0 and 30% at PEEP minErs in most respiratory cycles. Alveolar Tidal recruitment/derecruitment (%E 2   30) were predominant in the absence of PEEP and in PEEP levels higher than PEEP minErs , respectively. The slope of E rs (t) was different from zero in all groups besides PEEP minErs+4 . PEEP minErs presented the best compromise between alveolar tidal recruitment/derecruitment and overdistension, during 1 h of low-V T mechanical ventilation.

Mechanical ventilation with lower tidal volumes and positive end-expiratory pressure prevents alveolar coagulation in patients without lung injury

NARCIS (Netherlands)

Choi, Goda; Wolthuis, Esther K.; Bresser, Paul; Levi, Marcel; van der Poll, Tom; Dzoljic, Misa; Vroom, Margreeth B.; Schultz, Marcus J.

2006-01-01

BACKGROUND: Alveolar fibrin deposition is a hallmark of acute lung injury, resulting from activation of coagulation and inhibition of fibrinolysis. Previous studies have shown that mechanical ventilation with high tidal volumes may aggravate lung injury in patients with sepsis and acute lung injury.

Pressure correction schemes for compressible flows

International Nuclear Information System (INIS)

Kheriji, W.

2011-01-01

This thesis is concerned with the development of semi-implicit fractional step schemes, for the compressible Navier-Stokes equations; these schemes are part of the class of the pressure correction methods. The chosen spatial discretization is staggered: non conforming mixed finite elements (Crouzeix-Raviart or Rannacher-Turek) or the classic MA C scheme. An upwind finite volume discretization of the mass balance guarantees the positivity of the density. The positivity of the internal energy is obtained by discretizing the internal energy balance by an upwind finite volume scheme and b y coupling the discrete internal energy balance with the pressure correction step. A special finite volume discretization on dual cells is performed for the convection term in the momentum balance equation, and a renormalisation step for the pressure is added to the algorithm; this ensures the control in time of the integral of the total energy over the domain. All these a priori estimates imply the existence of a discrete solution by a topological degree argument. The application of this scheme to Euler equations raises an additional difficulty. Indeed, obtaining correct shocks requires the scheme to be consistent with the total energy balance, property which we obtain as follows. First of all, a local discrete kinetic energy balance is established; it contains source terms winch we somehow compensate in the internal energy balance. The kinetic and internal energy equations are associated with the dual and primal meshes respectively, and thus cannot be added to obtain a total energy balance; its continuous counterpart is however recovered at the limit: if we suppose that a sequence of discrete solutions converges when the space and time steps tend to 0, we indeed show, in 1D at least, that the limit satisfies a weak form of the equation. These theoretical results are comforted by numerical tests. Similar results are obtained for the baro-tropic Navier-Stokes equations. (author)

Density measurements under pressure for the binary system 1-propanol plus toluene

DEFF Research Database (Denmark)

Zeberg-Mikkelsen, Claus Kjær; Andersen, Simon Ivar

2005-01-01

and seven isobars up to 30 MPa. The uncertainty of the reported densities is less than 0.05%. The measured data has been used to study the influence of temperature, pressure, and composition on the isothermal compressibility and the isobaric thermal expansivity as well as the excess molar volume, which...... shows a complex sigmoid behavior involving both positive and negative values. This complex behavior has been interpreted as the result of changes in the free volume due to volume expansion and compressibility as a result of the breaking of hydrogen bonds of the self-associating alcohol molecules...

Infinite dilution partial molar volumes of platinum(II) 2,4-pentanedionate in supercritical carbon dioxide.

Science.gov (United States)

Kong, Chang Yi; Siratori, Tomoya; Funazukuri, Toshitaka; Wang, Guosheng

2014-10-03

The effects of temperature and density on retention of platinum(II) 2,4-pentanedionate in supercritical fluid chromatography were investigated at temperatures of 308.15-343.15K and pressure range from 8 to 40MPa by the chromatographic impulse response method with curve fitting. The retention factors were utilized to derive the infinite dilution partial molar volumes of platinum(II) 2,4-pentanedionate in supercritical carbon dioxide. The determined partial molar volumes were small and positive at high pressures but exhibited very large and negative values in the highly compressible near critical region of carbon dioxide. Copyright © 2014 Elsevier B.V. All rights reserved.

Estimation of vapour pressure and partial pressure of subliming ...

Indian Academy of Sciences (India)

Administrator

conditions of (total) pressure by using thermogravimetry under those conditions. Further, from the partial pressure P, it is possible to determine the number of moles of material in the vapour phase using the ideal gas equation, PV = nRT, where P is the partial pressure, V the volume, n number of moles (of the vapour), R the ...

Understanding the use of continuous oscillating positive airway pressure (bubble CPAP) to treat neonatal respiratory disease: an engineering approach.

Science.gov (United States)

Manilal-Reddy, P I; Al-Jumaily, A M

2009-01-01

A continuous oscillatory positive airway pressure with pressure oscillations incidental to the mean airway pressure (bubble CPAP) is defined as a modified form of traditional continuous positive airway pressure (CPAP) delivery where pressure oscillations in addition to CPAP are administered to neonates with lung diseases. The mechanical effect of the pressure oscillations on lung performance is investigated by formulating mathematical models of a typical bubble CPAP device and a simple representation of a neonatal respiratory system. Preliminary results of the respiratory system's mechanical response suggest that bubble CPAP may improve lung performance by minimizing the respiratory system impedance and that the resonant frequency of the respiratory system may be a controlling factor. Additional steps in terms of clinical trials and a more complex respiratory system model are required to gain a deeper insight into the mechanical receptiveness of the respiratory system to pressure oscillations. However, the current results are promising in that they offer a deeper insight into the trends of variations that can be expected in future extended models as well as the model philosophies that need to be adopted to produce results that are compatible with experimental verification.

Dew point, internal gas pressure, and chemical composition of the gas within the free volume of DWPF canistered waste forms

International Nuclear Information System (INIS)

Harbour, J.R.; Herman, D.T.; Crump, S.; Miller, T.J.; McIntosh, J.

1996-01-01

The Defense Waste Processing Facility (DWPF) produced 55 canistered waste forms containing simulated waste glass during the four Waste Qualification campaigns of the DWPF Startup Test Program. Testing of the gas within the free volume of these canisters for dew point, internal gas pressure, and chemical composition was performed as part of a continuing effort to demonstrate compliance with the Waste Acceptance Product Specifications. Results are presented for six glass-filled canisters. The dew points within the canisters met the acceptance criterion of < 20 degrees C for all six canisters. Factors influencing the magnitude of the dew point are presented. The chemical composition of the free volume gas was indistinguishable from air for all six canisters. Hence, no foreign materials were present in the gas phase of these canisters. The internal gas pressures within the sealed canisters were < 1 atm at 25 degrees C for all six canisters which readily met the acceptance criterion of an internal gas pressure of less than 1.5 atm at 25 degrees C. These results provided the evidence required to demonstrate compliance with the Waste Acceptance Product Specifications

Comparison of manual versus automatic continuous positive airway pressure titration and the development of a predictive equation for therapeutic continuous positive airway pressure in Chinese patients with obstructive sleep apnoea.

Science.gov (United States)

Luo, Jiaying; Xiao, Sichang; Qiu, Zhihui; Song, Ning; Luo, Yuanming

2013-04-01

Whether the therapeutic nasal continuous positive airway pressure (CPAP) derived from manual titration is the same as derived from automatic titration is controversial. The purpose of this study was to compare the therapeutic pressure derived from manual titration with automatic titration. Fifty-one patients with obstructive sleep apnoea (OSA) (mean apnoea/hypopnoea index (AHI) = 50.6 ± 18.6 events/h) who were newly diagnosed after an overnight full polysomnography and who were willing to accept CPAP as a long-term treatment were recruited for the study. Manual titration during full polysomnography monitoring and unattended automatic titration with an automatic CPAP device (REMstar Auto) were performed. A separate cohort study of one hundred patients with OSA (AHI = 54.3 ± 18.9 events/h) was also performed by observing the efficacy of CPAP derived from manual titration. The treatment pressure derived from automatic titration (9.8 ± 2.2 cmH(2)O) was significantly higher than that derived from manual titration (7.3 ± 1.5 cmH(2)O; P titration (54.3 ± 18.9 events/h before treatment and 3.3 ± 1.7 events/h after treatment; P titration pressure derived from REMstar Auto is usually higher than the pressure derived from manual titration. © 2013 The Authors. Respirology © 2013 Asian Pacific Society of Respirology.

Radio-nuclide angiocardiography combined with Swan-Ganz catheter for the estimation of volume-pressure curves of the pulmonary ''venous'' system in man

International Nuclear Information System (INIS)

Gotoh, K.; Hirakawa, S.; Suzuki, T.; Fujiwara, H.; Ohsumi, Y.; Yagi, Y.

1983-01-01

Short segments of volume-pressure (V-P) curves of the pulmonary ''venous'' (P''V'') system, consisting of the pulmonary veins and left atrium, were estimated in 31 patients. Pulmonary blood volume (PBV) was estimated by our new method, using RN-angiocardiography. Increments in PBV and mean pulmonary artery wedge (PAW) pressure, that occur during passive-elevation of both legs, were clues to the estimation of the compliance (ΔV/ΔP) of this system. Sublingual administration of nitroglycerin (NTG) caused the short segments of V-P curves to shift to the left almost horizontally but slightly downwards, associated with a considerable increase in ΔV/ΔP. It is suggested that NTG causes, among other things, relaxation of the walls of P''V'' system

Clinical predictors of central sleep apnea evoked by positive airway pressure titration

OpenAIRE

Bianchi, Matt; Gannon,Karen; Lovell,Kathy; Merlino,Margaret; Mojica,James; Moro,Marilyn

2016-01-01

Marilyn Moro,1 Karen Gannon,1 Kathy Lovell,1 Margaret Merlino,1 James Mojica,2 Matt T Bianchi,1,3 1Neurology Department, 2Pulmonary and Critical Care Medicine, Massachusetts General Hospital, Boston, MA, USA; 3Division of Sleep Medicine, Harvard Medical School, Boston, MA, USA Purpose: Treatment-emergent central sleep apnea (TECSA), also called complex apnea, occurs in 5%–15% of sleep apnea patients during positive airway pressure (PAP) therapy, but the clinical predictors are not w...

Body Composition Response to Lower Body Positive Pressure Training in Obese Children

OpenAIRE

Basant H. El-Refay; Nabeel T. Faiad

2014-01-01

Background: The high prevalence of obesity in Egypt has a great impact on the health care system, economic and social situation. Evidence suggests that even a moderate amount of weight loss can be useful. Aim of the study: To analyze the effects of lower body positive pressure supported treadmill training, conducted with hypocaloric diet, on body composition of obese children. Methods: Thirty children aged between 8 and 14 years, were randomly assigned into two groups: intervention group (15 ...

Pressure support ventilation vs Continuous positive airway pressure for treating of acute cardiogenic pulmonary edema: A pilot study.

Science.gov (United States)

Pagano, Antonio; Numis, Fabio G; Rosato, Valerio; Russo, Teresa; Porta, Giovanni; Bosso, Giorgio; Serra, Claudia; Masarone, Mario; Visone, Giuseppe; Paladino, Fiorella

2018-04-24

Non-invasive ventilation is usually adopted as a support to medical therapy in patients with acute pulmonary edema, but which modality between Pressure Support Ventilation (PSV) and Continuous Positive Airway Pressure (CPAP) has better favourable effects is not been yet well known. Aim of this observational study was to provide data on these different non-invasive ventilation modalities in the management of acute cardiogenic pulmonary edema. One-hundred-fifty-three patients consecutively admitted to the Emergency Room of two different Center were enrolled and randomly assigned to CPAP or PSV. Data relative to mortality, need of endotracheal intubation, sequential blood gas analysis were compared. Furthermore, there were no significant differences regarding mortality in the two groups, but patients treated with PSV had a significant lower rate of endotracheal intubation and a higher improvement of blood gas analyses parameters. In conclusion, our data support only a slight advantage in favour to PSV versus CPAP. Copyright © 2018 Elsevier B.V. All rights reserved.

High resolution gas volume change sensor

International Nuclear Information System (INIS)

Dirckx, Joris J. J.; Aernouts, Jef E. F.; Aerts, Johan R. M.

2007-01-01

Changes of gas quantity in a system can be measured either by measuring pressure changes or by measuring volume changes. As sensitive pressure sensors are readily available, pressure change is the commonly used technique. In many physiologic systems, however, buildup of pressure influences the gas exchange mechanisms, thus changing the gas quantity change rate. If one wants to study the gas flow in or out of a biological gas pocket, measurements need to be done at constant pressure. In this article we present a highly sensitive sensor for quantitative measurements of gas volume change at constant pressure. The sensor is based on optical detection of the movement of a droplet of fluid enclosed in a capillary. The device is easy to use and delivers gas volume data at a rate of more than 15 measurements/s and a resolution better than 0.06 μl. At the onset of a gas quantity change the sensor shows a small pressure artifact of less than 15 Pa, and at constant change rates the pressure artifact is smaller than 10 Pa or 0.01% of ambient pressure

Effects of respiratory rate, plateau pressure, and positive end-expiratory pressure on PaO2 oscillations after saline lavage.

Science.gov (United States)

Baumgardner, James E; Markstaller, Klaus; Pfeiffer, Birgit; Doebrich, Marcus; Otto, Cynthia M

2002-12-15

One of the proposed mechanisms of ventilator-associated lung injury is cyclic recruitment of atelectasis. Collapse of dependent lung regions with every breath should lead to large oscillations in PaO2 as shunt varies throughout the respiratory cycle. We placed a fluorescence-quenching PO2 probe in the brachiocephalic artery of six anesthetized rabbits after saline lavage. Using pressure-controlled ventilation with oxygen, ventilator settings were varied in random order over three levels of positive end-expiratory pressure (PEEP), respiratory rate (RR), and plateau pressure minus PEEP (Delta). Dependence of the amplitude of PaO2 oscillations on PEEP, RR, and Delta was modeled by multiple linear regression. Before lavage, arterial PO2 oscillations varied from 3 to 22 mm Hg. After lavage, arterial PO2 oscillations varied from 5 to 439 mm Hg. Response surfaces showed markedly nonlinear dependence of amplitude on PEEP, RR, and Delta. The large PaO2 oscillations observed provide evidence for cyclic recruitment in this model of lung injury. The important effect of RR on the magnitude of PaO2 oscillations suggests that the static behavior of atelectasis cannot be accurately extrapolated to predict dynamic behavior at realistic breathing frequencies.

[Clinical research of using optimal compliance to determine positive end-expiratory pressure].

Science.gov (United States)

Xu, Lei; Feng, Quan-sheng; Lian, Fu; Shao, Xin-hua; Li, Zhi-bo; Wang, Zhi-yong; Li, Jun

2012-07-01

To observe the availability and security of optimal compliance strategy to titrate the optimal positive end-expiratory pressure (PEEP), compared with quasi-static pressure-volume curve (P-V curve) traced by low-flow method. Fourteen patients received mechanical ventilation with acute respiratory distress syndrome (ARDS) admitted in intensive care unit (ICU) of Tianjin Third Central Hospital from November 2009 to December 2010 were divided into two groups(n = 7). The quasi-static P-V curve method and the optimal compliance titration were used to set the optimal PEEP respectively, repeated 3 times in a row. The optimal PEEP and the consistency of repeated experiments were compared between groups. The hemodynamic parameters, oxygenation index (OI), lung compliance (C), cytokines and pulmonary surfactant-associated protein D (SP-D) concentration in plasma before and 2, 4, and 6 hours after the experiment were observed in each group. (1) There were no significant differences in gender, age and severity of disease between two groups. (2)The optimal PEEP [cm H(2)O, 1 cm H(2)O=0.098 kPa] had no significant difference between quasi-static P-V curve method group and the optimal compliance titration group (11.53 ± 2.07 vs. 10.57 ± 0.87, P>0.05). The consistency of repeated experiments in quasi-static P-V curve method group was poor, the slope of the quasi-static P-V curve in repeated experiments showed downward tendency. The optimal PEEP was increasing in each measure. There was significant difference between the first and the third time (10.00 ± 1.58 vs. 12.80 ± 1.92, P vs. 93.71 ± 5.38, temperature: 38.05 ± 0.73 vs. 36.99 ± 1.02, IL-6: 144.84 ± 23.89 vs. 94.73 ± 5.91, TNF-α: 151.46 ± 46.00 vs. 89.86 ± 13.13, SP-D: 33.65 ± 8.66 vs. 16.63 ± 5.61, MAP: 85.47 ± 9.24 vs. 102.43 ± 8.38, CCI: 3.00 ± 0.48 vs. 3.81 ± 0.81, OI: 62.00 ± 21.45 vs. 103.40 ± 37.27, C: 32.10 ± 2.92 vs. 49.57 ± 7.18, all P safety and usability.

High pressure apparatus for hydrogen isotopes to pressures of 345 MPa (50,000 psi) and temperatures of 12000C

International Nuclear Information System (INIS)

Lakner, J.F.

1977-01-01

A functional new high pressure, high temperature apparatus for hydrogen isotopes uses an internally heated pressure vessel within a larger pressure vessel. The pressure capability is 345 MPa (50 K psi) at 1200 0 C. The gas pressure inside the internal vessel is balanced with gas pressure in the external vessel. The internal vessel is attached to a closure and is also the sample container. Our design allows thin-walled internal vessel construction and keeps the sample from ''seeing'' the furnace or other extraneous environment. The sample container together with the closure can easily be removed and loaded under argon using standard glove-box procedures. The small volume of the inner vessel permits small volumes of gas to be used, thus increasing the sensitivity during pressure-volume-temperature (PVT) work

Pressure-induced positive electrical resistivity coefficient in Ni-Nb-Zr-H glassy alloy

Science.gov (United States)

Fukuhara, M.; Gangli, C.; Matsubayashi, K.; Uwatoko, Y.

2012-06-01

Measurements under hydrostatic pressure of the electrical resistivity of (Ni0.36Nb0.24Zr0.40)100-xHx (x = 9.8, 11.5, and 14) glassy alloys have been made in the range of 0-8 GPa and 0.5-300 K. The resistivity of the (Ni0.36Nb0.24Zr0.40)86H14 alloy changed its sign from negative to positive under application of 2-8 GPa in the temperature range of 300-22 K, coming from electron-phonon interaction in the cluster structure under pressure, accompanied by deformation of the clusters. In temperature region below 22 K, the resistivity showed negative thermal coefficient resistance by Debye-Waller factor contribution, and superconductivity was observed at 1.5 K.

Related factors to semi-recumbent position compliance and pressure ulcers in patients with invasive mechanical ventilation: An observational study (CAPCRI study).

Science.gov (United States)

Llaurado-Serra, Mireia; Ulldemolins, Marta; Fernandez-Ballart, Joan; Guell-Baro, Rosa; Valentí-Trulls, Teresa; Calpe-Damians, Neus; Piñol-Tena, Angels; Pi-Guerrero, Mercedes; Paños-Espinosa, Cristina; Sandiumenge, Alberto; Jimenez-Herrera, María F

2016-09-01

Semi-recumbent position is recommended to prevent ventilator-associated pneumonia. Its implementation, however, is below optimal. We aimed to assess real semi-recumbent position compliance and the degree of head-of-bed elevation in Spanish intensive care units, along with factors determining compliance and head-of-bed elevation and their relationship with the development of pressure ulcers. Finally, we investigated the impact that might have the diagnosis of pressure ulcers in the attitude toward head-of-bed elevation. We performed a prospective, multicenter, observational study in 6 intensive care units. Inclusion criteria were patients ≥18 years old and expected to remain under mechanical ventilator for ≥48h. Exclusion criteria were patients with contraindications for semi-recumbent position from admission, mechanical ventilation during the previous 7 days and prehospital intubation. Head-of-bed elevation was measured 3 times/day for a maximum of 28 days using the BOSCH GLM80(®) device. The variables collected related to patient admission, risk of pressure ulcers and the measurements themselves. Bivariate and multivariate analyses were carried out using multiple binary logistic regression and linear regression as appropriate. Statistical significance was set at preplacement therapy, nursing shift, open abdomen, abdominal vacuum therapy and agitation. Twenty-five patients (9.1%) developed a total of 34 pressure ulcers. The diagnosis of pressure ulcers did not affect the head-of-bed elevation. In the multivariate analysis, head-of-bed elevation was not identified as an independent risk factor for pressure ulcers. Semi-recumbent position compliance is below optimal despite the fact that it seems achievable most of the time. Factors that affect semi-recumbent position include the particular intensive care unit, abdominal conditions, renal replacement therapy, agitation and bed type. Head-of-bed elevation was not related to the risk of pressure ulcers. Efforts

Osmosis-Based Pressure Generation: Dynamics and Application

Science.gov (United States)

Li, Suyi; Billeh, Yazan N.; Wang, K. W.; Mayer, Michael

2014-01-01

This paper describes osmotically-driven pressure generation in a membrane-bound compartment while taking into account volume expansion, solute dilution, surface area to volume ratio, membrane hydraulic permeability, and changes in osmotic gradient, bulk modulus, and degree of membrane fouling. The emphasis lies on the dynamics of pressure generation; these dynamics have not previously been described in detail. Experimental results are compared to and supported by numerical simulations, which we make accessible as an open source tool. This approach reveals unintuitive results about the quantitative dependence of the speed of pressure generation on the relevant and interdependent parameters that will be encountered in most osmotically-driven pressure generators. For instance, restricting the volume expansion of a compartment allows it to generate its first 5 kPa of pressure seven times faster than without a restraint. In addition, this dynamics study shows that plants are near-ideal osmotic pressure generators, as they are composed of many small compartments with large surface area to volume ratios and strong cell wall reinforcements. Finally, we demonstrate two applications of an osmosis-based pressure generator: actuation of a soft robot and continuous volume delivery over long periods of time. Both applications do not need an external power source but rather take advantage of the energy released upon watering the pressure generators. PMID:24614529