Inhomogeneity during deflation of excised canine lungs. III. Single-breath O2 tests

1988 ◽  
Vol 65 (4) ◽  
pp. 1775-1781
Author(s):  
D. O. Warner ◽  
R. E. Hyatt ◽  
K. Rehder
Keyword(s):  
Dead Space ◽  
Vertical Gradient ◽  
Pleural Pressure ◽  
Phase Iii ◽  
Flow Limitation ◽  
Single Breath ◽  
Expired Gas ◽  
Expiratory Flow ◽  
Phase Iv

Both interregional and intraregional mechanisms may cause changes in N2 concentration of expired gas during the phases of the single-breath O2 test (SBO2) that follow dead-space washout. To evaluate the possible importance of each mechanism, we performed the SBO2 in excised canine lungs that were first suspended in air and then immersed in stable foams that simulated the vertical gradient of pleural pressure. The lungs were deflated at constant submaximal flows. The slope of phase III diminished with increasing expiratory flow and increased with foam immersion. The onset of phase IV depended on flow, and a terminal decrease in N2 concentration (phase V) was often observed. Simultaneously measured estimates of regional flows and volumes (J. Appl. Physiol. 65: 1764-1774, 1988) were used to further interpret these results. The onset of phase IV at flows greater than quasi-static signified the onset of flow limitation of dependent regions. The onset of phase V corresponded to flow limitation of nondependent regions.

Phase V of the single-breath washout test

1982 ◽  
Vol 52 (1) ◽  
pp. 34-43 ◽  
Author(s):  
G. M. Nichol ◽  
D. B. Michels ◽  
H. J. Guy
Keyword(s):  
Flow Rate ◽  
Flow Limitation ◽  
Tracer Gas ◽  
Flow Rates ◽  
Single Breath ◽  
Lower Lung ◽  
Expiratory Flow ◽  
The Difference ◽  
Expiratory Flow Rates ◽  
Phase Iv

A downward-deflecting phase V is often seen following the phase IV terminal rise in the single-breath N2 washout test (SB N2). This phase V was studied in eight normal nonsmoking subjects aged 27–41, using both the SB N2 test and single-breath washouts of boluses of inert tracer gas slowly inhaled from residual volume (RV). All of the subjects showed a distinct phase V in both tests. Expiratory flow rates between 0.1 and 2.0 1/s were used; at each flow rate phase V appeared shortly after expiration became flow limited. Thus the volume above RV at which phase V began increased with increasing expiratory flow rate. The difference between the exhaled volumes at which flow became limited and phase V appeared was shown to be approximately equal to the anatomic dead space. This behavior is predicted by a model of lung emptying in a gravitational field. As expiration proceeds, flow limitation occurs first in the (tracer-poor) lower lung regions and then progresses toward the (tracer-rich) upper lung regions causing phase IV. When all lung regions have finally become flow limited, the amount of flow from the upper regions decreases relative to that of the lower regions, thereby causing phase V.

Influence of expiratory flow rate on "closing volume" measurement

1979 ◽  
Vol 46 (5) ◽  
pp. 1011-1015 ◽  
Author(s):  
D. P. Osmanliev ◽  
P. K. Popov
Keyword(s):  
Flow Rate ◽  
Normal Subjects ◽  
Volume Measurement ◽  
Closing Volume ◽  
Flow Limitation ◽  
Airway Closure ◽  
Dynamic Flow ◽  
Expiratory Flow ◽  
Phase Iv

The influence of expiratory flow rate (VE) on the onset of phase IV was studied in 15 normal subjects. VE was controlled voluntarily and varied between 0.2 and 2.5 l/s. All subjects showed significantly higher values for CV/VC, % at expiratory flow rate of 1.0 and 1.5 l/s, compared to those estimated at 0.2 l/s. The correlation between CV and volume of flow limitation (VFL) was also studied. For most of the subjects a considerable disagreement between the two values at very low VE was found. At higher flows, however, CV and VFL agreed well. Our results indicate that CV measurement is markedly influenced by VE in the range 0.2--1.5 l/s. This finding gives further support to the hypothesis that CV is determined in part by dynamic flow-limiting properties of the lung as well as by true airway closure.

Gravitational independence of single-breath washout tests in recumbent dogs

1988 ◽  
Vol 64 (2) ◽  
pp. 642-648 ◽  
Author(s):  
S. Tomioka ◽  
S. Kubo ◽  
H. J. Guy ◽  
G. K. Prisk
Keyword(s):  
Prone Position ◽  
Regional Distribution ◽  
Transpulmonary Pressure ◽  
Phase Iii ◽  
Closing Volume ◽  
Body Rotation ◽  
Single Breath ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Phase Iv

To examine the mechanisms of lung filling and emptying, Ar-bolus and N2 single-breath washout tests were conducted in 10 anesthetized dogs (prone and supine) and in three of those dogs with body rotation. Transpulmonary pressure was measured simultaneously, allowing identification of the lung volume above residual volume at which there was an inflection point in the pressure-volume curve (VIP). Although phase IV for Ar was upward, phase IV for N2 was small and variable, especially in the prone position. No significant prone to supine differences in closing capacity for Ar were seen, indicating that airway closure was generated at the same lung volumes. The maximum deflections of phase IV for Ar and N2 from extrapolated phase III slopes were smaller in the prone position, suggesting more uniform tracer gas concentrations across the lungs. VIP was smaller than the closing volume for Ar, which is consistent with the effects of well-developed collateral ventilation in dogs. Body rotation tests in three dogs did not generally cause an inversion of phase III or IV. We conclude that in recumbent dogs regional distribution of ventilation is not primarily determined by the effect of gravity, but by lung, thorax, and mediastinum interactions and/or differences in regional mechanical properties of the lungs.

Inhomogeneity of pulmonary ventilation during sustained microgravity as determined by single-breath washouts

1994 ◽  
Vol 76 (4) ◽  
pp. 1719-1729 ◽  
Author(s):  
H. J. Guy ◽  
G. K. Prisk ◽  
A. R. Elliott ◽  
R. A. Deutschman ◽  
J. B. West
Keyword(s):  
Vital Capacity ◽  
Normal Gravity ◽  
Parabolic Flight ◽  
Pulmonary Ventilation ◽  
Phase Iii ◽  
Single Breath ◽  
Relative Contribution ◽  
Cardiogenic Oscillations ◽  
Expiratory Flow Rates ◽  
Phase Iv

Gravity is known to cause inhomogeneity of ventilation. Nongravitational factors are also recognized, but their relative contribution is not understood. We therefore studied ventilatory inhomogeneity during sustained microgravity during the 9-day flight of Spacelab SLS-1. All seven crew members performed single-breath nitrogen washouts. They inspired a vital capacity breath of 100% oxygen with a bolus of argon at the start of inspiration, and the inspiratory and expiratory flow rates were controlled at 0.5 l/s. Control measurements in normal gravity (1 G) were made pre- and postflight in the standing and supine position. Compared with the standing 1-G measurements, there was a marked decrease in ventilatory inhomogeneity during microgravity, as evidenced by the significant reductions in cardiogenic oscillations, slope of phase III, and height of phase IV for nitrogen and argon. However, argon phase IV volume was not reduced, and considerable ventilatory inhomogeneity remained. For example, the heights of the cardiogenic oscillations during microgravity for nitrogen and argon were 44 and 24%, respectively, of their values at 1 G, whereas the slopes of phase III for nitrogen and argon were 78 and 29%, respectively, of those at 1 G. The presence of a phase IV in microgravity is strong evidence that airway closure still occurs in the absence of gravity. The results were qualitatively similar to those found previously during short periods of 0 G in parabolic flight.

Regional distribution of ventilation at residual volume in induced bronchospasm

1982 ◽  
Vol 53 (2) ◽  
pp. 361-366
Author(s):  
L. Delaunois ◽  
R. Boileau ◽  
J. Diodatti ◽  
J. Gauthier ◽  
R. R. Martin
Keyword(s):  
Lung Volume ◽  
Regional Distribution ◽  
Phase Iii ◽  
Residual Volume ◽  
Single Breath ◽  
Airway Opening ◽  
Collateral Pathways ◽  
Total Lung Resistance ◽  
Downward Slope ◽  
Phase Iv

The regional distribution of a bolus of gas inhaled at residual volume (RV) is attributed to regional airway closure and is responsible for the phase IV of the single-breath washout during the following deflation. As bronchospasm increases the range of airway opening pressures through the lung, the regional distribution of the bolus could change with effects on the shape of the single-breath washout. We investigated the regional distribution of boluses inhaled at RV and their single-breath washouts during methacholine-induced bronchospasm in prone dogs. With increasing total lung resistance (RL) we first observed in five out of eight animals a preferential “redistribution” of the bolus to the upper caudal regions of the lung, which could be partially attributed to the increased lung volume at RV. When maximal RL was attained, the bolus was evenly distributed through all regions of the lung in these animals with disappearance of phase IV and increased slope of phase III, and a final decrease of tracer concentration at low lung volumes was observed. We conclude from these data that increased bronchomotor tone in dogs results in a less homogeneous intraregional distribution of the bolus with increased slope of phase III and in a more even interregional distribution leading to disappearance of phase IV. In severe bronchospasm the downward slope at low lung volume suggests intraregional closed lung units emptying through collateral pathways into still open neighboring units.

Single-breath nitrogen test in excised human lungs

1981 ◽  
Vol 51 (6) ◽  
pp. 1568-1573 ◽  
Author(s):  
N. Berend ◽  
C. Skoog ◽  
W. M. Thurlbeck
Keyword(s):  
Transpulmonary Pressure ◽  
Phase Iii ◽  
Peripheral Airways ◽  
Single Breath ◽  
Human Lungs ◽  
Peripheral Airway ◽  
Normal Lungs ◽  
Airway Dimensions ◽  
Phase Iv

Pressure-volume curves and simulated single-breath nitrogen tests were performed on 32 excised left human lungs and the slope of phase III, and phase IV plus minimal volume, expressed as percent of the lung volume at a transpulmonary pressure of 30 cmH2O (closing capacity), was calculated. The lungs were graded as to the degree of emphysema and degree of peripheral airways disease. Peripheral airway dimensions were also measured. The closing capacity expressed as percent predicted in vivo was significantly correlated with the total pathological scores (P less than 0.01) and inflammation scores (P less than 0.01) as well as the transpulmonary pressures at the onset of phase IV (P less than 0.01). Correlations with the emphysema grade were not significant. The slopes of phase III were highly variable even among normal lungs and could not be shown to correlate with airways disease or emphysema.

Effect of posture on the single-breath oxygen test in normal subjects

1976 ◽  
Vol 41 (4) ◽  
pp. 474-479 ◽  
Author(s):  
D. A. Cortese ◽  
J. R. Rodarte ◽  
K. Rehder ◽  
R. E. Hyatt
Keyword(s):  
Prone Position ◽  
Normal Subjects ◽  
Standing Position ◽  
Phase Iii ◽  
Linear Gradient ◽  
Considerable Similarity ◽  
Single Breath ◽  
Normal People ◽  
Lateral Decubitus ◽  
Phase Iv

The effect of posture on phase III (alveolar nitrogen plateau) and phase IV (closing capacity) of the single-breath oxygen test was examined in 10 normal people. In part 1 of the study, subjects inspired and expired in the standing, supine, prone, and right lateral decubitus positions; there was no effect of posture on phase IV but slopes of phase III were higher when subjects were in the supine and lateral positions. In part 2, subjects inspired in the standing position and expired in one of the recumbent positions. Phase IV occurred infrequently except in the prone position (6 of 10 subj); slopes of phase III in part 2 were not consistently altered by changing posture. It is difficult to explain the failure of posture to alter phase IV solely on a model requiring a linear gradient of pleural pressure. The slope of phase III appears to depend more on the emptying patterns of small regions with widely varying volume-to-ventilation ratios than on gravity-dependent sequences of emptying. Finally, the data suggest a considerable similarity between the upright and prone positions in terms of lung filling and emptying.

Pulmonary Function Abnormalities in Thalassemia Patients on a Hypertransfusion Program

PEDIATRICS ◽  
1980 ◽  
Vol 65 (5) ◽  
pp. 1013-1017
Author(s):  
Thomas G. Keens ◽  
Margaret H. O'Neal ◽  
Jorge A. Ortega ◽  
Carol B. Hyman ◽  
Arnold C.G. Platzker
Keyword(s):  
Carbon Monoxide ◽  
Pulmonary Function ◽  
Total Lung Capacity ◽  
Small Airway ◽  
Phase Iii ◽  
Diffusing Capacity ◽  
Lung Capacity ◽  
Nitrogen Washout ◽  
Single Breath ◽  
Expiratory Flow

Pulmonary function tests were performed in 12 thalassemia patients on a hypertransfusion program (age 18.4 ± 2.6 SEM years) to determine the presence of any abnormalities of lung function. These included spirometry, expiratory flow rates, body plethysmography, single-breath nitrogen washout, single breath carbon monoxide diffusing capacity, and arterial blood gases. Only one patient had normal pulmonary function. Arterial hypoxemia was present in ten of 12 patients at rest. The total lung capacity (TLC) was normal. The residual volume was abnormally increased in five of 12 patients. The slope of phase III of single breath nitrogen washout curve was abnormal in five of 12 patients, but the closing volume was normal. The maximal expiratory flow rate at 60% total lung capacity was decreased in four of 12 patients, suggesting the presence of small airway disease. The single breath carbon monoxide diffusing capacity was normal in all patients. These pulmonary function abnormalities did not correlate with age or the cumulative amount of iron via blood transfused. The small airway obstruction, hyperinflation; and hypoxemia observed in thalassemia patients on a hypertransfusion program may result from the basic disease, iron deposition in the lungs, or other factors.

Influence of expiratory flow on closing capacity at low expiratory flow rates

1975 ◽  
Vol 39 (1) ◽  
pp. 60-65 ◽  
Author(s):  
J. R. Rodarte ◽  
R. E. Hyatt ◽  
D. A. Cortese
Keyword(s):  
Lung Volume ◽  
Normal Subjects ◽  
Closing Volume ◽  
Residual Volume ◽  
Dependent Lung ◽  
Flow Rates ◽  
Single Breath ◽  
Expiratory Flow ◽  
Expiratory Flow Rates ◽  
Phase Iv

Single-breath oxygen (SBO2) tests at expiratory flow rates of 0.2, 0.5, and 1.01/s were performed by 10 normal subjects in a body plethysmograph. Closing capacity (CC)--the absolute lung volume at which phase IV began--increased significantly with increases in flow. Five subjects were restudied with a 200-ml bolus of 100% N2 inspired from residual volume after N2 washout by breathing 100% O2 and similar results were obtained. An additional five subjects performed SBO2 tests in the standing, supine, and prone positions; closing volume (CV)--the lung volume above residual volume at which phase IV began--also increased with increases of expiratory flow. The observed increase in CC with increasing flow did not appear to result from dependent lung regions reaching some critical “closing volume” at a higher overall lung volume. In normal subjects, the phase IV increase in NI concentration may be caused by the asynchronous onset of flow limitation occurring initially in dependent regions.

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