Effect of intrathoracic pressure on pressure-volume characteristics of the lung in man

1975 ◽  
Vol 38 (3) ◽  
pp. 411-417 ◽  
Author(s):  
H. S. Goldberg ◽  
W. Mitzner ◽  
K. Adams ◽  
H. Menkes ◽  
S. Lichtenstein ◽  
...  
Keyword(s):  
Negative Pressure ◽  
Total Lung Capacity ◽  
Human Subjects ◽  
Ambient Pressure ◽  
Intrathoracic Pressure ◽  
Dynamic Compliance ◽  
Positive Pressure ◽  
Lung Capacity ◽  
Airway Opening ◽  
Volume Characteristics

Quasi-static pressure-volume (P-V) curves in normal seated human subjects were determined with pressure at the airway opening (Pa0) set below (negative pressure), above (positive pressure), or equal to ambient pressure. Dynamic compliance (Cdyn) during controlled continuous negative pressure breathing (CNPB) was also studied. Quasi-static P-V curves at negative pressure were decreased in slope, reflected a decrease in total lung capacity, and intersected the P-V curve obtained at ambient Pa0. At positive pressure the P-V curves showed an increase in slope and an increase in total lung capacity. During CNPB a fall in Cdyn was found. The fall in Cdyn was rapid and persisted for the duration of CNPB. Cdyn promptly returned to control levels when Pa0 was adjusted to ambient pressure.

Effect of continuous pressure breathing on right ventricular volumes

1967 ◽  
Vol 22 (6) ◽  
pp. 1053-1060 ◽  
Author(s):  
Maylene Wong ◽  
Edgardo E. Escobar ◽  
Gilberto Martinez ◽  
John Butler ◽  
Elliot Rapaport
Keyword(s):  
Right Ventricular ◽  
Negative Pressure ◽  
Atmospheric Pressure ◽  
Diastolic Pressure ◽  
Venous Pressure ◽  
Intrathoracic Pressure ◽  
Transmural Pressure ◽  
Positive Pressure ◽  
End Diastolic Volume ◽  
Negative Pressure Breathing

We measured the end-diastolic volume (EDV) and stroke volume (SV) in the right ventricle of anesthetized dogs during continuous pressure breathing and compared them to measurements taken during breathing at atmospheric pressure. During intratracheal positive-pressure breathing, EDV, and SV decreased and end-diastolic pressure became more positive relative to atmospheric pressure. During intratracheal negative-pressure breathing, EDV enlarged and SV tended to increase; end-diastolic pressure became more negative. During extrathoracic negative-pressure breathing SV decreased, EDV fell, though not significantly, and end-diastolic pressure rose, but insignificantly. Changes in EDV observed during intratracheal positive-pressure breathing and intratracheal negative-pressure breathing were associated with minor shifts in transmural pressure (end-diastolic pressure minus intrapleural pressure) in the expected directions, but during extrathoracic negative-pressure breathing a large increase in transmural pressure took place with the nonsignificant reduction in EDV. We believe that intrathoracic pressure influences right ventricular filling by changing the peripheral-to-central venous pressure gradient. The cause of the alteration in diastolic ventricular distensibility demonstrated during extra-thoracic negative-pressure breathing remains unexplained. positive-pressure breathing; negative-pressure breathing; extrathoracic negative-pressure breathing Submitted on August 16, 1966

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

1985 ◽  
Vol 59 (4) ◽  
pp. 1242-1248 ◽  
Author(s):  
J. D. Marks ◽  
J. M. Luce ◽  
N. M. Lazar ◽  
J. N. Wu ◽  
A. Lipavsky ◽  
...  
Keyword(s):  
Lung Volume ◽  
Negative Pressure ◽  
Ambient Pressure ◽  
Pressure Control ◽  
Positive Pressure ◽  
Healthy Humans ◽  
Human Lungs ◽  
Solute Uptake ◽  
Residual Capacity ◽  
Negative Pressure Breathing

To study the effect of increases in lung volume on solute uptake, we measured clearance of 99mTc-diethylenetriaminepentaacetic acid (Tc-DTPA) at different lung volumes in 19 healthy humans. Seven subjects inhaled aerosol (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.

Pressure-volume characteristics of excised human lungs: effects of sex, age, and emphysema

1980 ◽  
Vol 49 (4) ◽  
pp. 558-565 ◽  
Author(s):  
N. Berend ◽  
C. Skoog ◽  
W. M. Thurlbeck
Keyword(s):  
Body Length ◽  
Total Lung Capacity ◽  
Transpulmonary Pressure ◽  
Lung Volumes ◽  
Lung Capacity ◽  
Human Lungs ◽  
Males And Females ◽  
Group 2 ◽  
Volume Characteristics

Static deflationary pressure-volume curves were obtained in 28 emphysema-free (18 male and 10 female) and 39 emphysematous excised human lungs inflated to a maximum transpulmonary pressure (Pl) of 30 cmH2O. In emphysema-free lungs, the lung volumes at Pl 30 cmH2O (V30) were significantly related to body length in males and were significantly larger than predicated total lung capacity in vivo. However, corrected for stature (V30/body length), there was no significant age correlation. In both males and females, highly significant correlations between the PL at 50--90% V30 and age were obtained. There were no significant differences in these regressions between males and females. The emphysematous lungs were divided into three groups with increasing emphysema grades. Progressive decreases in the PL at 50--90% V30 and increases in the V30 were seen in the groups with increasing degrees of emphysema. Significant changes occurred in these measurements even in group 2 with mild emphysema, suggesting that the lesions of emphysema are not directly responsible for these changes.

Tracking variations in airway caliber by using total respiratory vs. airway resistance in healthy and asthmatic subjects

2003 ◽  
Vol 95 (2) ◽  
pp. 511-518 ◽  
Author(s):  
L. D. Black ◽  
R. Dellacà ◽  
K. Jung ◽  
H. Atileh ◽  
E. Israel ◽  
...  
Keyword(s):  
Chest Wall ◽  
Airway Resistance ◽  
Total Lung Capacity ◽  
Recursive Least Squares ◽  
Effective Diameter ◽  
Tidal Breathing ◽  
Lung Capacity ◽  
Airway Caliber ◽  
Esophageal Balloon ◽  
Airway Opening

An index of airway caliber can be tracked in near-real time by measuring airway resistance (Raw) as indicated by lung resistance at 8 Hz. These measurements require the placing of an esophageal balloon. The objective of this study was to establish whether total respiratory system resistance (Rrs) could be used rather than Raw to track airway caliber, thereby not requiring an esophageal balloon. Rrs includes the resistance of the chest wall (Rcw). We used a recursive least squares approach to track Raw and Rrs at 8 Hz in seven healthy and seven asthmatic subjects during tidal breathing and a deep inspiration (DI). In both subject groups, Rrs was significantly higher than Raw during tidal breathing at baseline and postchallenge. However, at total lung capacity, Raw and Rrs became equivalent. Measured with this approach, Rcw appears volume dependent, having a magnitude of 0.5–1.0 cmH2O · l-1 · s during tidal breathing and decreasing to zero at total lung capacity. When resistances are converted to an effective diameter, Rrs data overestimate the increase in diameter during a DI. Simulation studies suggest that the decrease in apparent Rcw during a DI is a consequence of airway opening flow underestimating chest wall flow at increased lung volume. We conclude that the volume dependence of Rcw can bias the presumed net change in airway caliber during tidal breathing and a DI but would not distort assessment of maximum airway dilation.

Pulmonary function alterations after 3 wk of exposure to hypobaria and/or hypoxia in growing rats

1995 ◽  
Vol 78 (5) ◽  
pp. 1787-1792 ◽  
Author(s):  
H. S. Sekhon ◽  
J. L. Wright ◽  
W. M. Thurlbeck
Keyword(s):  
Lung Function ◽  
Forced Vital Capacity ◽  
Hypobaric Hypoxia ◽  
Vital Capacity ◽  
Total Lung Capacity ◽  
Ambient Pressure ◽  
Normobaric Hypoxia ◽  
Lung Growth ◽  
Lung Capacity ◽  
Expiratory Flow

We studied lung growth in rats between 4 and 7 wk of age under different conditions. There were five groups, seven animals in each: 1) general controls (ambient pressure and room air, food ad libitum); 2) hypobaric normoxic [barometric pressure (PB) 410 mmHg, PO2 153 Torr]; 3) normobaric hypoxic (ambient pressure, PO2 80 Torr); 4) hypobaric hypoxic (PB 410 mmHg, PO2 80 Torr); and 5) weight-matched controls to hypobaric hypoxic. Residual volume, functional residual capacity, vital capacity, and total lung capacity grew 10–20% more in both hypoxic groups than in weight-matched and general controls. Expiratory flow rates corrected for forced vital capacity decreased, and specific airway resistance increased significantly. In addition, the ratio of forced expiratory volume in 0.1 s to %forced vital capacity, peak expiratory flow rate, and forced maximal midexpiratory flow were also lower in normobaric hypoxic animals compared with weight-matched controls. Above a transpulmonary pressure of 6 cmH2O, flows were reduced in both hypoxic groups. No differences were observed between hypobaric normoxic and general control groups for lung volume and lung function. In weight-matched animals, total lung capacity decreased but lung function remained unchanged. We conclude that accelerated lung growth in hypobaric hypoxia and normobaric hypoxia is dysanaptic. Lung growth in hypobaric hypoxia is primarily induced by low oxygen, but differences between hypobaric hypoxia and normobaric hypoxia suggest a beneficial effect of low pressure.

scholarly journals Vacuum-Actuated Bending for Grasping

Robotics ◽  
2018 ◽  
Vol 7 (4) ◽  
pp. 73
Author(s):  
Jay Miller ◽  
Nathan Wicks
Keyword(s):  
Negative Pressure ◽  
Atmospheric Pressure ◽  
Ambient Pressure ◽  
Positive Pressure ◽  
Cellular Solids ◽  
Pressure Application ◽  
Bending Actuator ◽  
Robotic Devices ◽  
Good Agreement

Soft robotic devices typically are actuated with the application of a positive pressure (compared to ambient pressure), but some exciting work has been done with negative pressure application, with advantages for safety and robustness. Here, we present a negative pressure bending actuator inspired by previous work by Yang et al., fabricated using rapid prototyping techniques and elastomeric polymers. We describe the mechanical behavior of the system from a cellular solids perspective, showing the steps needed for the analysis and characterization of future similar systems. We find good agreement between experimentally measured values of displacement and force generated in atmospheric pressure conditions.

scholarly journals Influence of lung volume on pulmonary microvascular pressure-volume characteristics

2000 ◽  
Vol 89 (4) ◽  
pp. 1591-1600 ◽  
Author(s):  
George P. Topulos ◽  
Richard E. Brown ◽  
James P. Butler
Keyword(s):  
Lung Volume ◽  
Total Lung Capacity ◽  
Lung Volumes ◽  
Vascular Volume ◽  
Lung Capacity ◽  
Transit Times ◽  
Wide Range ◽  
Residual Capacity ◽  
Volume Characteristics ◽  
Lung Microcirculation

The pressure-volume (P-V) characteristics of the lung microcirculation are important determinants of the pattern of pulmonary perfusion and of red and white cell transit times. Using diffuse light scattering, we measured capillary P-V loops in seven excised perfused dog lobes at four lung volumes, from functional residual capacity (FRC) to total lung capacity (TLC), over a wide range of vascular transmural pressures (Ptm). At Ptm 5 cmH2O, specific compliance of the microvasculature was 8.6%/cmH2O near FRC, decreasing to 2.7%/cmH2O as lung volume increased to TLC. At low lung volumes, the vasculature showed signs of strain stiffening (specific compliance fell as Ptm rose), but stiffening decreased as lung volume increased and was essentially absent at TLC. The P-V loops were smooth without sharp transitions, consistent with vascular distension as the primary mode of changes in vascular volume with changes in Ptm. Hysteresis was small (0.013) at all lung volumes, suggesting that, although surface tension may set basal capillary shape, it does not strongly affect capillary compliance.

Effect of inflation on microvascular pressures in lungs of young rabbits

1987 ◽  
Vol 252 (1) ◽  
pp. H80-H84 ◽  
Author(s):  
J. U. Raj ◽  
P. Chen ◽  
L. Navazo
Keyword(s):  
Vascular Resistance ◽  
Lung Volume ◽  
Total Lung Capacity ◽  
Important Variable ◽  
Longitudinal Distribution ◽  
Positive Pressure ◽  
Lung Inflation ◽  
Lung Capacity ◽  
Pulmonary Arterial ◽  
Lung Blood Flow

We have examined the effect of positive pressure inflation on the longitudinal distribution of vascular resistance and intravascular pressures in isolated blood-perfused lungs of 3- to 4-wk-old rabbits. Lungs were perfused in zone 3 at airway inflation pressures (P airway) of 6, 14, and 19 cmH2O (pleural pressure, atmospheric) corresponding to 60, 80, and 90% of total lung capacity. We measured microvascular pressures by the micropipette servo-nulling technique in 20- to 50-microns diameter subpleural arterioles and venules. Pulmonary arterial and left atrial pressures were also measured. Lung blood flow was kept constant at 145 +/- 18 ml X kg body wt-1 X min-1. We found that at P airway of 6 cmH2O, approximately 55% of the total pressure drop was in arteries, approximately 23% in microvessels, and approximately 22% in veins. With increasing P airway and lung volume, there was a significant decrease in arterial and venous resistance, but an increase in resistance in microvessels. We conclude that lung inflation significantly alters the distribution of segmental vascular resistance, and therefore lung volume is an important variable that should be considered during estimation of capillary filtration pressure.

Flow Dependence of the Intrapulmonary Distribution of Inspired Boluses of 133Xe in Smokers and Non-Smokers

1972 ◽  
Vol 43 (3) ◽  
pp. 319-329 ◽  
Author(s):  
R. R. Martin ◽  
N. R. Anthonisen ◽  
M. Zutter
Keyword(s):  
Vital Capacity ◽  
Total Lung Capacity ◽  
Dynamic Compliance ◽  
Flow Rates ◽  
Time Constants ◽  
Peripheral Airways ◽  
Lung Capacity ◽  
Flow Dependence ◽  
Young Smokers ◽  
Older Subjects

1. Starting at 50% vital capacity, boluses of 133Xe were inhaled either at very low or maximal flow rates, the inspiration terminating at total lung capacity (TLC). Flow-dependent changes in bolus distribution were examined by measuring regional radioctivity and computing regional time-constants, and also by recording alveolar plateaux during the subsequent vital capacity expiration. Regional residual volumes, as a fraction of regional total lung capacities, were also calculated. Three groups of subjects were studied: young non-smokers, young cigarette smokers, and older non-smokers. 2. All three groups gave similar results in terms of regional time-constants though there was less variation in the results for young non-smokers. 3. Regional residual volumes also gave similar results in all groups although again there was less variation in young non-smokers. In young smokers, residual volumes in some regions depended on the flow rate used in their measurement, which indicated intraregional inhomogeneity of function. 4. In young non-smokers alveolar plateaux after slow and fast bolus inspirations differed little; this was not the case either in older subjects or in smokers. The increased flow-dependence of the alveolar plateau is analogous with the increased frequency-dependence of dynamic compliance and probably indicates obstruction of small peripheral airways.

Absence of effects of hypoxia on small airway function in humans

1979 ◽  
Vol 47 (2) ◽  
pp. 251-256 ◽  
Author(s):  
R. S. Goldstein ◽  
N. Zamel ◽  
A. S. Rebuck
Keyword(s):  
Total Lung Capacity ◽  
Human Subjects ◽  
Small Airway ◽  
Healthy Human ◽  
Lung Capacity ◽  
Airway Function ◽  
Healthy Human Subjects ◽  
Maximum Expiratory Flow ◽  
Gas Dilution ◽  
Hypoxic Mixtures

We measured the effects of sustained isocapnic hypoxia (PAO2 = 40--50 Torr; PACO2 = 38--42 Torr) on tests sensitive to small airway function in healthy human subjects. Maximum expiratory flow-volume curves on air, nitrogen-hypoxic, helium-normoxic, and helium-hypoxic mixtures as well as closing volumes while subjects breathed air and a hypoxic mixture were obtained. We then measured total lung capacity (TLC), both plethysmographically and by inert gas dilution, and used the nonplethysmographic method to measure the effects of hypoxia on TLC. In none of these tests were there any statistically significant changes when values obtained during hypoxia were compared with those during normoxia. It is suggested that previous reports that indicated that TLC was increased by hypoxia might have arisen from a plethysmographic artifact.

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