Role of alveolar recruitment in lung inflation: influence on pressure-volume hysteresis

1983 ◽  
Vol 55 (4) ◽  
pp. 1321-1332 ◽  
Author(s):  
G. C. Smaldone ◽  
W. Mitzner ◽  
H. Itoh
Keyword(s):  
Lung Volume ◽  
Linear Dimension ◽  
Total Lung Capacity ◽  
Alveolar Recruitment ◽  
Rapid Cycling ◽  
Lung Inflation ◽  
Lung Capacity ◽  
History Of

The behavior of terminal lung units (alveoli) with changes in lung volume is controversial. For example, different investigators using similar techniques have suggested that alveoli expand homogeneously or, conversely, get smaller with increases in lung volume. We studied this problem by filling excised dog lobes with monodisperse aerosol and observing deposition at zero airflow. Under these conditions, the deposition of particles is inversely proportional to a mean alveolar linear dimension (ALD). With this technique, changes in ALD were assessed as the lung ventilated along its pressure-volume (PV) curve. PV curves were generated using a rapid cycling technique that minimized trapping and allowed reversible regulation of inflation-deflation hysteresis. Irreversible changes in PV hysteresis were assessed by rinsing the lung with Tween. With significant PV hysteresis, the ALD progressively decreased with inflation to total lung capacity (TLC). With deflation from TLC, the ALD was unchanged until low volumes were reached, when it decreased markedly. When PV hysteresis was minimized (reversibly or irreversibly), inflation and deflation ALD were superimposed. These data are consistent with progressive alveolar recruitment with inflation to TLC and derecruitment with deflation. The correlation between alveolar dimensions and PV hysteresis suggests that shifts in the PV curve can be accounted for by changes in the population of units. The number open at any given point is determined by the dynamic history of inflation.

Effect of volume and volume history of the lungs on pulmonary shunt flow

1964 ◽  
Vol 207 (1) ◽  
pp. 235-238 ◽  
Author(s):  
Nicholas R. Anthonisen
Keyword(s):  
Lung Volume ◽  
Total Lung Capacity ◽  
Full Range ◽  
Transpulmonary Pressure ◽  
Pulmonary Shunt ◽  
Shunt Flow ◽  
Lung Capacity ◽  
Surface Active Properties ◽  
History Of ◽  
Surface Active

Relative pulmonary shunt flow (Qs/Qt), was measured in denitrogenated open-chested cats during apnea over the full range of lung volumes. The particular lung volume and transpulmonary pressure were also measured. When completely collapsed lungs were inflated, Qs/Qt decreased sharply to 3% at total lung capacity (TLC). During deflation from TLC Qs/Qt was insensitive to changes in lung volume. Qs/Qt remained low during reinflation after deflation from TLC. These changes in shunt flow can be interpreted as due to either recruitment or collapse of gas exchange units during lung volume change. It appears that completely collapsed lungs inflate very unevenly but that deflation from TLC proceeds remarkably evenly. Reinflation after deflation from TLC also seems to proceed evenly, and the manifest pressure-volume hysteresis is most likely due to hysteresis of the surface-active properties of the alveolar lining material.

Airway response to deep inspiration: role of inflation pressure

2001 ◽  
Vol 91 (6) ◽  
pp. 2574-2578 ◽  
Author(s):  
Robert H. Brown ◽  
Wayne Mitzner
Keyword(s):  
Healthy Subjects ◽  
Total Lung Capacity ◽  
Qualitative Change ◽  
Intrinsic Properties ◽  
High Resolution Computed Tomography ◽  
Lung Inflation ◽  
Lung Capacity ◽  
Airway Caliber ◽  
Airway Response

Deep inspirations (DIs) have been shown to have both bronchoprotective and bronchodilator effects in healthy subjects; however, the bronchodilator effects of a DI appear to be impaired in asthmatic compared with healthy subjects. Because the ability to generate high transpulmonary pressures at total lung capacity depends on both the lung properties and voluntary effort, we wondered how the response of airways to DI might be altered if the maneuver were done with less than maximal inflation. The present work was undertaken to examine the effects of varying the magnitude of lung inflation during the DI maneuver on subsequent airway caliber. In five anesthetized and ventilated dogs during methacholine infusion, changes in airway size after DIs of increasing magnitude were measured over the subsequent 5-min period using high-resolution computed tomography. Results show that the magnitude of lung inflation is extremely important, leading to a qualitative change in the airway response. A large DI (45 cmH2O airway pressure) caused subsequent airway dilation, whereas smaller DIs (≤35 cmH2O) caused bronchoconstriction. The precise mechanism underlying these observations is uncertain, but it seems to be related to an interaction between intrinsic properties of the contracted airway smooth muscle and the response to mild stretch.

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.

Role of expiratory flow limitation in determining lung volumes and ventilation during exercise

1999 ◽  
Vol 86 (4) ◽  
pp. 1357-1366 ◽  
Author(s):  
Steven R. McClaran ◽  
Thomas J. Wetter ◽  
David F. Pegelow ◽  
Jerome A. Dempsey
Keyword(s):  
Lung Volume ◽  
Dead Space ◽  
Maximal Exercise ◽  
Total Lung Capacity ◽  
Esophageal Pressure ◽  
Maximal Flow ◽  
Expiratory Flow Limitation ◽  
Lung Capacity ◽  
Flow Volume Loop

We determined the role of expiratory flow limitation (EFL) on the ventilatory response to heavy exercise in six trained male cyclists [maximal O2 uptake = 65 ± 8 (range 55–74) ml ⋅ kg−1 ⋅ min−1] with normal lung function. Each subject completed four progressive cycle ergometer tests to exhaustion in random order: two trials while breathing N2O2(26% O2-balance N2), one with and one without added dead space, and two trials while breathing HeO2 (26% O2-balance He), one with and one without added dead space. EFL was defined by the proximity of the tidal to the maximal flow-volume loop. With N2O2during heavy and maximal exercise, 1) EFL was present in all six subjects during heavy [19 ± 2% of tidal volume (Vt) intersected the maximal flow-volume loop] and maximal exercise (43 ± 8% of Vt), 2) the slopes of the ventilation (ΔV˙e) and peak esophageal pressure responses to added dead space (e.g., ΔV˙e/[Formula: see text], where [Formula: see text] is end-tidal[Formula: see text]) were reduced relative to submaximal exercise, 3) end-expiratory lung volume (EELV) increased and end-inspiratory lung volume reached a plateau at 88–91% of total lung capacity, and 4) Vt reached a plateau and then fell as work rate increased. With HeO2 (compared with N2O2) breathing during heavy and maximal exercise, 1) HeO2 increased maximal flow rates (from 20 to 38%) throughout the range of vital capacity, which reduced EFL in all subjects during tidal breathing, 2) the gains of the ventilatory and inspiratory esophageal pressure responses to added dead space increased over those during room air breathing and were similar at all exercise intensities, 3) EELV was lower and end-inspiratory lung volume remained near 90% of total lung capacity, and 4) Vt was increased relative to room air breathing. We conclude that EFL or even impending EFL during heavy and maximal exercise and with added dead space in fit subjects causes EELV to increase, reduces the Vt, and constrains the increase in respiratory motor output and ventilation.

Static Lung Volumes in Singers

1973 ◽  
Vol 82 (1) ◽  
pp. 89-95 ◽  
Author(s):  
Wilbur J. Gould ◽  
Hiroshi Okamura
Keyword(s):  
Lung Volume ◽  
Total Lung Capacity ◽  
The Other ◽  
Lung Volumes ◽  
Lung Capacity ◽  
Vocal Training ◽  
Professional Singers ◽  
Professional Singer ◽  
Singing Ability

It has long been assumed that the superior vocal ability of the trained professional singer arose from a higher than average breathing capacity and consequent above-normal ventilatory efficiency. However, until now, it has not been clear whether this presumed superior pulmonary capacity and breathing efficiency arose from training, from heredity, or from other factors. To clarify the role of training (and by inference that of other factors also) upon the capacity for singing, various indices reflecting static lung volumes, as distinguished from dynamic parameters measured during the act of singing, in trained professional singers, students of voice and subjects with no vocal training, were compared. Results indicated that contrary to reports by others, there were no significant differences in the total lung capacity (TLC) of the trained professional singer and that of the other two groups when allowances were made for age and sex; but when the ability to mobilize or utilize TLC was compared, it was found that the trained singer was much better able to do this than either of the other two groups. Specifically, it was found that the ratio of the residual lung volume (RV) (the amount of air remaining in the lungs at the end of a total voluntary expiration) to TLC was lower in the trained singer than in the students of voice, and that these students, in turn, had a lower RV/TLC ratio than the untrained subjects. These findings, therefore, suggest that the increased singing ability of the trained professional singer arises in large part from the ability to increase breathing efficiency by reducing the residual lung volume and, further, that this ability tends to improve with length of vocal training.

Rib cage and abdominal restrictions have different effects on lung mechanics

1980 ◽  
Vol 49 (6) ◽  
pp. 946-952 ◽  
Author(s):  
C. A. Bradley ◽  
N. R. Anthonisen
Keyword(s):  
Lung Volume ◽  
Total Lung Capacity ◽  
Lung Mechanics ◽  
Elastic Recoil ◽  
Rib Cage ◽  
Lung Capacity ◽  
Single Breath ◽  
Restrictive Procedures ◽  
Maximum Expiratory Flow ◽  
Per Se

The effects of a variety of restrictive procedures on lung mechanics were studied in eight healthy subjects. Rib cage restriction decreased total lung capacity (TLC) by 43% and significantly increased elastic recoil and maximum expiratory flow (MEF). Subsequent immersion of four subjects with rib cage restriction resulted in no further change in either parameter; shifts of blood volume did not reverse recoil changes during rib cage restriction. Abdominal restriction decreased TLC by 40% and increased MEF and elastic recoil, but recoil was increased significantly less than was the case with rib cage restriction. Further, at a given recoil pressure, MEF was less during rib cage restriction than during either abdominal restriction or no restriction. Measurements of the unevenness of inspired gas distribution by the single-breath nitrogen technique showed increased unevenness during rib cage restriction, which was significantly greater than that during abdominal restriction. We conclude that lung volume restriction induces changes in lung function, but the nature of these changes depends on how the restriction is applied and therefore cannot be ascribed to low lung volume breathing per se.

Inspiratory muscles during exercise: a problem of supply and demand

1988 ◽  
Vol 64 (6) ◽  
pp. 2482-2489 ◽  
Author(s):  
P. Leblanc ◽  
E. Summers ◽  
M. D. Inman ◽  
N. L. Jones ◽  
E. J. Campbell ◽  
...  
Keyword(s):  
Lung Volume ◽  
Static Pressure ◽  
Total Lung Capacity ◽  
Supply And Demand ◽  
Normal Subjects ◽  
Esophageal Pressure ◽  
Maximum Exercise ◽  
Lung Capacity ◽  
Inspiratory Muscles ◽  
Residual Capacity

The capacity of inspiratory muscles to generate esophageal pressure at several lung volumes from functional residual capacity (FRC) to total lung capacity (TLC) and several flow rates from zero to maximal flow was measured in five normal subjects. Static capacity was 126 +/- 14.6 cmH2O at FRC, remained unchanged between 30 and 55% TLC, and decreased to 40 +/- 6.8 cmH2O at TLC. Dynamic capacity declined by a further 5.0 +/- 0.35% from the static pressure at any given lung volume for every liter per second increase in inspiratory flow. The subjects underwent progressive incremental exercise to maximum power and achieved 1,800 +/- 45 kpm/min and maximum O2 uptake of 3,518 +/- 222 ml/min. During exercise peak esophageal pressure increased from 9.4 +/- 1.81 to 38.2 +/- 5.70 cmH2O and end-inspiratory esophageal pressure increased from 7.8 +/- 0.52 to 22.5 +/- 2.03 cmH2O from rest to maximum exercise. Because the estimated capacity available to meet these demands is critically dependent on end-inspiratory lung volume, the changes in lung volume during exercise were measured in three of the subjects using He dilution. End-expiratory volume was 52.3 +/- 2.42% TLC at rest and 38.5 +/- 0.79% TLC at maximum exercise.

Costal diaphragm curvature in the dog

1993 ◽  
Vol 75 (2) ◽  
pp. 527-533 ◽  
Author(s):  
A. M. Boriek ◽  
S. Liu ◽  
J. R. Rodarte
Keyword(s):  
Mechanical Ventilation ◽  
Muscle Fiber ◽  
Lung Volume ◽  
Spontaneous Breathing ◽  
Total Lung Capacity ◽  
Muscle Fibers ◽  
Transdiaphragmatic Pressure ◽  
Lung Capacity ◽  
Principal Axes ◽  
Quadratic Surface

The curvature of the midcostal region of the diaphragm in seven dogs was determined at functional residual capacity (FRC) and end inspiration during spontaneous breathing and mechanical ventilation and at total lung capacity in the prone and supine positions. Metallic markers were attached to muscle fibers on the abdominal surface of the diaphragm, and the dog was allowed to recover from surgery. The three-dimensional positions of the markers were determined by biplane videofluoroscopy. A quadratic surface was fit to the bead positions. The principal axes of the quadratic surface lie nearly along and perpendicular to the muscle fibers. In both the supine and prone positions, the values of the principal curvatures were similar at FRC and end inspiration during spontaneous breathing, when muscle tension and transdiaphragmatic pressure both increase with increasing lung volume, and during mechanical ventilation and passive inflation to total lung capacity, when both decrease relative to their magnitude at FRC. No abrupt change of curvature, which might be expected at the edge of the zone of apposition, was apparent. The curvature along the muscle fiber was 0.35 +/- 0.07 cm-1; the curvature perpendicular to the muscle fiber was much smaller, 0.06 +/- 0.01 cm-1. The costal region of the diaphragm displaces and shortens as lung volume increases, but its shape, as described by its curvatures, does not change substantially.

Elastic properties of the lung in acute induced asthma

1983 ◽  
Vol 54 (1) ◽  
pp. 152-158 ◽  
Author(s):  
D. Rodenstein ◽  
D. C. Stanescu
Keyword(s):  
Lung Volume ◽  
Static Pressure ◽  
Total Lung Capacity ◽  
Esophageal Pressure ◽  
Elastic Recoil ◽  
Rapid Loss ◽  
Asthmatic Patients ◽  
Clear Cut ◽  
Lung Capacity ◽  
Significant Change

In acute induced asthma, plethysmographic total lung capacity (TLCm) was reported to increase and lung elastic recoil [Pst(L)] to decrease. The increase in TLC is spurious (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 52: 939–954, 1982), so that the rapid loss in Pst(L) could be due to errors in lung volume. We studied seven asthmatic patients before and during an induced bronchospasm. TLC was derived simultaneously from mouth and esophageal pressure vs. plethysmographic volume plots (TLCm and TLCes, respectively). Before bronchospasm, TLCm and TLCes were similar. During bronchospasm average TLCm increased, from 7.30 +/- 1.34 (SD) to 8.12 +/- 1.49 liters (P less than 0.001), whereas TLCes did not (P greater than 0.60). Static pressure-volume curves, derived from TLCes (P-Ves), were superimposed on prechallenge curves or only slightly shifted to the left, whereas those derived from TLCm (P-Vm) showed a clear-cut parallel shift to the left. At 70% of control TLC there was no significant change in Pst(L) measured from P-Ves curves (7.3 +/- 3.1 cmH2O before bronchospasm; 6.7 +/- 2.3 cmH2O during bronchospasm, P greater than 0.10), whereas Pst(L) measured from P-Vm curves decreased from 7.3 +/- 3.1 to 5.1 +/- 2.4 cmH2O (P less than 0.01). No significant change in Pst(L) at TLC was observed during bronchospasm. We conclude that in our patients acute decrease in Pst(L) during induced asthma was artifactual, secondary to lung volume overestimation by body plethysmography.

Factors determining degree of inflation in intratracheally fixed rat lungs

1980 ◽  
Vol 48 (2) ◽  
pp. 389-393 ◽  
Author(s):  
G. Hayatdavoudi ◽  
J. D. Crapo ◽  
F. J. Miller ◽  
J. J. O'Neil
Keyword(s):  
Slow Rate ◽  
Total Lung Capacity ◽  
Formaldehyde Solution ◽  
Initial Flow ◽  
Lung Inflation ◽  
Lung Capacity ◽  
Final Degree ◽  
Low Rate

The total lung capacity (TLC) of rats was measured in vivo and was compared to the displacement volume of the lungs following intratracheal fixation with glutaraldehyde or formaldehyde solution. When glutaraldehyde was used the speed of infusion of the fixative was an important factor in the final degree of lung inflation achieved. With a low rate of fixative infusion and a final pressure of 20 cm of fixative the glutaraldehyde-fixed lungs inflated to 55% TLC. With a high initial flow of glutaraldehyde and a final pressure of 20 cm of fixative the lungs inflated to 84% TLC. Fixation of lungs inside the intact chest wall was found to result in a higher degree of inflation. With a reservoir height of 20 cm and a low rate of fixative infusion lungs fixed in situ reached 74% TLC, whereas lungs fixed in situ, but from animals that have been exsanguinated prior to fixation, inflated to only 58% TLC. This suggests that the volume of the blood in the lungs prior to infusion of glutaraldehyde influences the degree of inflation achieved. Formaldehyde-fixed lungs required 72 h to be completely fixed and they were inflated to 90% TLC when a reservoir height of 20 cm was used. Because of the slow rate of fixation using with formaldehyde solution the rate of infusion was found not to limit the degree of inflation that could be achieved.

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