Regional ventilation in excised lobes exposed to a transpulmonary pressure gradient

1988 ◽  
Vol 64 (2) ◽  
pp. 771-780 ◽  
Author(s):  
D. O. Warner ◽  
R. E. Hyatt ◽  
K. Rehder
Keyword(s):  
Pressure Gradient ◽  
Lung Volume ◽  
Inflection Point ◽  
Transpulmonary Pressure ◽  
Accurate Estimate ◽  
Airway Closure ◽  
Single Breath ◽  
Lower Lung ◽  
The Relationship ◽  
Phase Iv

We performed the quasi-static single-breath oxygen test (SBO2) in 16 excised canine lower lung lobes while the lobes were first suspended in air and then later immersed in stable foams that provided a vertical transpulmonary pressure gradient. In lobes suspended in air, an approximately linear alveolar plateau (AP) was obtained. The AP during foam immersion was markedly curvilinear, with phase IV seen at end expiration. The observed AP during foam immersion could be predicted by a mathematical model that assumed a homogeneous transpulmonary pressure-regional volume relationship equal to the overall pressure-volume (PV) relationship measured with the lobe suspended in air. The accuracy of this model was further confirmed by measuring the washout of nitrogen injected into different lung regions through alveolar capsules. We also used the model to examine the relationship between the onset of dependent airway closure and two of its proposed indicators: the onset of phase IV and the inflection point of the overall PV relationship. In most lobes, the lung volume at the onset of phase IV was less than the modeled lung volume at dependent airway closure. The lung volume at the inflection point was always less than the modeled lung volume at dependent airway closure. We show that the overall PV relationship measured in lobes suspended in air provides an accurate estimate of regional PV relationships during foam immersion.

Comparison of airway closure measured in vivo and from single-breath washout curve

1981 ◽  
Vol 50 (3) ◽  
pp. 587-596 ◽  
Author(s):  
H. Susskind ◽  
H. L. Atkins ◽  
J. F. Klopper ◽  
A. N. Ansari ◽  
P. Richards
Keyword(s):  
Excellent Agreement ◽  
Normal Subjects ◽  
Scintillation Camera ◽  
Airway Closure ◽  
Single Breath ◽  
Health And Disease ◽  
Limiting Case ◽  
The Relationship ◽  
Phase Iv

The volume of air trapped (Vat) in alveoli subtended by airways closed at residual volume (RV) was correlated with the volume of air left in the lungs at the start of airway closure (CC) in a clinical study of 13 patients with a variety of pulmonary disorders and 5 normal subjects. Vat was quantitated at RV from the in vivo distribution differences between 127Xe inspired as a bolus and again after equilibrium; CC was measured from the inflection point on the single-breath washout curve at the onset of phase IV. 127Xe activity was measured with a scintillation camera, and activity profiles were obtained for 28-45 consecutive 6.5-mm horizontal lung slices between base and apex. Three well-defined regions were found: A, in the upper lung, all of whose airways remained completely open; B, located above the base and containing both open and closed airways; and C, above the base, all of whose airways were closed. Of the Vat of 0.43 liter for the normals, 41% was located in region C. For the patients, the values were 59% of 0.59 liter. The relationship between the onset of phase IV and regional airway closure was confirmed for normals as well as patients. A statistically significant increase in closure was found for the patients over the normals. Excellent agreement was obtained between Vat/TLC (total lung capacity) and CC/TLC (r = 0.79, P less than 0.001) for normals as well as patients, and CC appears to reflect regional airway closure in both health and disease. Similar excellent agreement was obtained for the normals between lung height with closed airways and CC/TLC (r = 0.88, P less than 0.001). Vat appears to be the most important physiological determinant of phase IV, the value at RV representing the limiting case.

Airway closure and reopening assessed by the alveolar capsule oscillation technique

1996 ◽  
Vol 80 (6) ◽  
pp. 2077-2084 ◽  
Author(s):  
D. R. Otis ◽  
F. Petak ◽  
Z. Hantos ◽  
J. J. Fredberg ◽  
R. D. Kamm
Keyword(s):  
Lung Volume ◽  
Input Impedance ◽  
Transpulmonary Pressure ◽  
Closing Volume ◽  
Airway Closure ◽  
Breathing Cycle ◽  
Abrupt Increase ◽  
Consistent Effect ◽  
Peripheral Airways

An alveolar capsule oscillation technique was used to determine 1) the lobe pressure and volume at which airways close and reopen, 2) the effect of expiration rate on closing volume and pressure, 3) the phase in the breathing cycle at which airway closure occurs, and 4) the site of airway closure. Experiments were conducted in excised dog lobes; closure was detected by an abrupt increase in the input impedance of surfacemounted alveolar capsules. Mean transpulmonary pressure (Ptp) at closure was slightly less than zero (Ptp = -2.3 cmH2O); the corresponding mean reopening pressure was Ptp = 14 cmH2O. The expiration rate varied between 1 and 20% of total lobe capacity per second and had no consistent effect on the closing volume and pressure. When lung volume was cycled up to frequencies of 0.2 Hz, closure generally occurred on expiration rather than inspiration. These observations support the conclusion that mechanical collapse, rather than meniscus formation, is the most likely mechanism producing airway closure in normal excised dog lungs. Analysis of measured acoustic impedances and reopening pressures suggests that closure occurs in the most peripheral airways. Reopening during inspiration was often observed to consist of a series of stepwise decreases in capsule impedance, indicating a sequence of opening events.

Inflection point on transpulmonary pressure-volume curves and closing volume

1975 ◽  
Vol 38 (2) ◽  
pp. 228-235 ◽  
Author(s):  
M. Demedts ◽  
J. Clement ◽  
D. C. Stanescu ◽  
K. P. van de Woestijne
Keyword(s):  
Inflection Point ◽  
Vital Capacity ◽  
Transpulmonary Pressure ◽  
Bronchial Obstruction ◽  
Closing Volume ◽  
Lung Volumes ◽  
Nitrogen Washout ◽  
Single Breath ◽  
Space Effect ◽  
Washout Curves

In 20 healthy subjects and 18 patients with bronchial obstruction, closing volume (CV) on single-breath nitrogen washout curves and inflection point (IP) on transpulmonary pressure-volume curves were recorded simultaneously during slow expiratory vital capacity maneuvers. IP and CV did not occur at identical lung volumes, IP being systematically larger than CV for small CV values. This discrepancy could not be attributed to an esophageal or mediastinal artifact. It is suggested that, though CV and IP both express “airway closure,” their sensitivity to closure may differ: CV underestimates closure because of a dead space effect; the latter may vary individually. On the other hand, IP may not reflect the true beginning of closure, particularly when it occurs at higher lung volumes.

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.

Airway closure and closing volume

1979 ◽  
Vol 46 (1) ◽  
pp. 24-30 ◽  
Author(s):  
L. Forkert ◽  
S. Dhingra ◽  
N. R. Anthonisen
Keyword(s):  
Blood Flow ◽  
Lung Volume ◽  
Regional Perfusion ◽  
Phase Iii ◽  
Breath Hold ◽  
Closing Volume ◽  
Residual Volume ◽  
Airway Closure ◽  
Lung Volumes ◽  
Phase Iv

Using boluses of radioactive Xe we compared regional N2O uptake with regional perfusion distribution during open glottis breath hold in five seated men. Measurements were made near residual volume, at closing volume (CV), above CV and when possible, between CV and residual volume (RV). At low lung volumes basal N2O uptake was small whereas basal blood flow was not. This discrepancy was interpreted as evidence of airway closure and was quantitated. All subjects showed extensive basal closure near RV. At closing volume four of five subjects demonstrated closure and some closure was evident in these subjects at volumes in excess of CV. The increase in airway closure with decreasing lung volume was much greater below CV than above it. Conventional CV tracings were obtained using helium boluses; the height of phase IV was positively correlated with the change in airway closure between CV and RV as assessed by the N2O technique. The slope of phase III did not correlate with the amount of airway closure measured at CV. We concluded that the conventionally measured CV is not the volume at which airway closure begins but that the onset of phase IV reflects an increase in basal airway closure and the height of phase IV reflects the amount of basal closure between CV and RV.

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.

Collateral ventilation in excised human lungs

1981 ◽  
Vol 50 (5) ◽  
pp. 927-930 ◽  
Author(s):  
N. Berend ◽  
C. Skoog ◽  
W. M. Thurlbeck
Keyword(s):  
Airway Closure ◽  
Single Breath ◽  
Human Lungs ◽  
Inflection Points ◽  
Total Lack ◽  
The Difference ◽  
Collateral Ventilation ◽  
Phase Iv

Pressure-volume (PV) curves and single-breath nitrogen (SBN) washout traces were obtained in 32 excised human lungs. Comparison of the volumes at the onset of phage IV of the SBN traces (V phase IV) and the volumes at the inflection points (VIP) of the PV curves revealed V phase IV to be significantly larger than VIP. We postulated that V phase IV was caused by bulk airway closure and that the difference between V phase IV and VIP was due to collateral ventilation. To test this we correlated V phas IV -- VIP with age and emphysema grades of the lungs. Significant correlations were obtained, demonstrating that with increasing age and emphysema grade V phase IV -- VIP also increased. This is consistent with the documented evidence for decreased resistance to collateral ventilation with increasing age and emphysema. In addition, in a total of 86 lungs we demonstrated that with increasing age and emphysema there is an increasing incidence of total lack of sigmoid deviation in the PV curve.

Airway closure with methacholine-induced bronchoconstriction

1987 ◽  
Vol 63 (6) ◽  
pp. 2223-2230 ◽  
Author(s):  
R. B. Filuk ◽  
D. J. Berezanski ◽  
N. R. Anthonisen
Keyword(s):  
Lung Volume ◽  
Total Lung Capacity ◽  
Relative Increase ◽  
Pulmonary Perfusion ◽  
Airway Closure ◽  
Lung Capacity ◽  
Single Breath ◽  
Washout Curves

We examined airway closure with methacholine-induced bronchoconstriction in eight normal seated adults at a mean lung volume of 39% total lung capacity. Closure was evaluated in two ways. Regional closure was examined by comparing the regional distributions of 133Xe boluses distributed according to N2O uptake with those distributed by pulmonary perfusion; regions that exhibited less N2O uptake than perfusion were interpreted as having airway closure. In addition, we measured single-breath washouts of the same boluses; differences between the washouts indicated closure that was not necessarily regional. Basal airway closure increased with methacholine inhalation from 21 +/- 3 to 46 +/- 4% (means +/- SE; P less than 0.001). This was due to both decreased basal N2O uptake and a relative increase of basal perfusion. Washout curves of boluses distributed by perfusion did not change with bronchoconstriction. Before bronchoconstriction, washouts of boluses distributed by N2O uptake did not differ significantly from those distributed by perfusion. During bronchoconstriction, single-breath washouts of boluses distributed by N2O uptake showed increased concentration differences (P less than 0.015) that were significantly greater than those resulting from boluses delivered by perfusion. Changes in basal closure did not correlate with washout changes. We conclude that methacholine inhalation induced bronchoconstriction-increased basal airway closure and also increased airway closure in other lung regions in a way that did not relate to basal closure.

Characteristics of inspiratory inhibition by phasic volume feedback in cats

1978 ◽  
Vol 45 (1) ◽  
pp. 80-86 ◽  
Author(s):  
M. K. Younes ◽  
J. E. Remmers ◽  
J. Baker
Keyword(s):  
Lung Volume ◽  
Time Dependent ◽  
Inspiratory Time ◽  
Reversible Inhibition ◽  
Single Breath ◽  
Inspiratory Phase ◽  
Inspiratory Activity ◽  
The Relationship ◽  
Obvious Relation ◽  
Volume Range

The dependence of phrenic efferent discharge on vagal-volume feedback was examined in barbiturate-anesthetized, paralyzed cats ventilated by a phrenic-driven servo respirator. The characteristics of the respiratory were altered for a single breath, and the resulting change in phrenic activity was quantitated by comparison with phrenic activity without phasic volume feedback. The relation between volume feedback and phrenic inhibition was determined both when inspiratory termination occurred during the rising phase of phrenic discharge and during the plateau observed with barbiturate-induced apneusis. Inhibition of inspiratory activity occurred only when lung volume exceeded a time-dependent threshold. Above this threshold, andextending over a substantial volume range, volume feedback caused graded and reversible inhibition of phrenic discharge. The threshold for graded inhibition declined progressively during the inspiratory phase, showing no obvious relation to the level of inspiratory activity. At any particular time, the relation between volume and phrenic inhibition was convex to the volume axis, and the slope of the relationship increased with inspiratory time. The results indicate that a) volume feedback inhibits inspiration in a graded manner, b) partial inhibition of phrenic activity renders it more susceptible to additional inhibition, and c) inhibitory effectiveness of volume feedback increases with time.

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