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.

Influence of collateral ventilation on single-breath washout curves

1988 ◽  
Vol 64 (1) ◽  
pp. 429-434 ◽  
Author(s):  
S. Tomioka ◽  
S. Kubo ◽  
H. J. Guy ◽  
G. K. Prisk
Keyword(s):  
Transpulmonary Pressure ◽  
Phase Iii ◽  
Closing Volume ◽  
Single Breath ◽  
Age Related ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Washout Curves ◽  
Collateral Ventilation ◽  
Phase Iv

To examine the relationship between airway closure and collateral ventilation, Ar bolus single-breath washout tests were performed in the supine position in 10 mature dogs (animals with a well-developed collateral ventilation). Transpulmonary pressure was measured simultaneously to obtain the volume above residual volume of the inflection point in the pressure-volume curve (VIP). In pigs, closing volume (CV/VC%, mean 27.4%, where VC is vital capacity) equaled the volume of inflection (VIP/VC%, mean 35.1%) when the dead space (0.07 liter) was accounted for, indicating simultaneous onset. In dogs, closing volume (CV/VC%, mean 48.1%) was greater than the volume of inflection (VIP/VC%, mean 27%). Furthermore, as closing volume increased, so did the volume exhaled between closing volume and the volume of inflection [(CV-VIP)/VC%]. These increases were strongly age related, with the oldest dogs showing the greatest differences between closing volume and volume of inflection. These results support the previous suggestion that this difference is a measure of the degree of collateral ventilation. We defined a concavity index (CI) of phase IV by measuring the ratio of the end-to-mid phase IV height above extrapolated phase III (no concavity implies CI = 2). Whereas pigs had a low CI (mean 3.3), dogs had a high CI (mean 10.6). In dogs, the CI correlated well with closing volume (CV/VC%) and the volume exhaled between closing volume and volume of inflection [(CV-VIP)/VC%]. Again, this relationship was strongly dependent on age, suggesting that the CI is also a valid indication of the degree of collateral ventilation.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

scholarly journals Acute effects of long-acting bronchodilators on small airways detected in COPD patients by single-breath N2 test and lung P-V curve

2017 ◽  
Vol 123 (5) ◽  
pp. 1266-1275 ◽  
Author(s):  
Matteo Pecchiari ◽  
Pierachille Santus ◽  
Dejan Radovanovic ◽  
Edgardo DʼAngelo
Keyword(s):  
Chronic Obstructive Pulmonary Disease ◽  
Pulmonary Disease ◽  
Phase Iii ◽  
Chronic Obstructive ◽  
Closing Volume ◽  
Small Airways ◽  
Acute Effects ◽  
Obstructive Pulmonary Disease ◽  
Single Breath ◽  
Volume Curve

Small airways represent the key factor of chronic obstructive pulmonary disease (COPD) pathophysiology. The effect of different classes of bronchodilators on small airways is still poorly understood and difficult to assess. Hence the acute effects of tiotropium (18 µg) and indacaterol (150 µg) on closing volume (CV) and ventilation inhomogeneity were investigated and compared in 51 stable patients (aged 70 ± 7 yr, mean ± SD; 82% men) with moderate to very severe COPD. Patients underwent body plethysmography, arterial blood gas analysis, tidal expiratory flow limitation (EFL), dyspnea assessment, and simultaneous recording of single-breath N2 test and transpulmonary pressure-volume curve (PL-V), before and 1 h after drug administration. The effects produced by indacaterol on each variable did not differ from those caused by tiotropium, independent of the severity of disease, assessed according to the Global Initiative for Chronic Obstructive Pulmonary Disease (GOLD) scale and the presence of EFL. Bronchodilators significantly decreased the slope of phase III and CV (−5 ± 4 and −2.5 ± 2.1%, respectively, both P < 0.001), with an increase in both slope and height of phase IV and of the anatomical dead space. Arterial oxygen pressure and saturation significantly improved (3 ± 3 mmHg and 2 ± 2%, respectively, both P < 0.001); their changes negatively correlated with those of phase III slope ( r = −0.659 and r = −0.454, respectively, both P < 0.01). The vital capacity (VC) increased substantially, but the PL-V/VC curve above CV was unaffected. In conclusion, bronchodilators reduce the heterogeneity of peripheral airway mechanical properties and the extent of their closure, with minor effects on critical closing pressure. This should lessen the risk of small-airway damage and positively affect gas exchange. NEW & NOTEWORTHY This is the first study investigating in stable chronic obstructive pulmonary disease patients the acute effects of two long-acting bronchodilators, a β-agonist and a muscarinic antagonist, on peripheral airways using simultaneous lung pressure-volume curve and single-breath N2 test. By lessening airway mechanical property heterogeneity, both drugs similarly reduced ventilation inhomogeneity and extent of small-airway closure, as indicated by the decrease of phase III slope, increased oxygen saturation, and fall of closing volume, often below expiratory reserve volume.

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.

Improved measurements of shear modulus and pleural membrane tension of the lung

1979 ◽  
Vol 47 (1) ◽  
pp. 175-181 ◽  
Author(s):  
M. A. Hajji ◽  
T. A. Wilson ◽  
S. J. Lai-Fook
Keyword(s):  
Shear Modulus ◽  
Transpulmonary Pressure ◽  
Elastic Half Space ◽  
Concentrated Force ◽  
Membrane Area ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Pressure Independent ◽  
Work Done ◽  
The Continuum

The continuum solution for the deformation of an elastic half space covered by a membrane is used to interpret measurements of the indentation of lung lobes under a column of fluid. The shear modulus mu of the underlying parenchyma is found to be approximately 0.7 times transpulmonary pressure, independent of species size. The tension in the pleural membrane T increases rapidly with increasing membrane area. For dog lungs, the value of T is 10(3) to 10(4) dyn/cm. For the larger species tested, pigs and horses, T is larger. The continuum solution shows that a concentrated force applied to the pleural surface is distributed over a distance T/mu as it is transmitted across the pleural membrane. The membrane is important in determining the displacement produced by forces that act within a region that is small compared to this distance, approximately 2 cm for dog lungs. By comparing the tension-area curve of the pleural membrane with the pressure-volume curve of the lobe, it is found that the pleural membrane contributes about 20% of the work done by the lung during deflation.

Evidence for increased intrathoracic fluid volume in man at high altitude

1979 ◽  
Vol 47 (4) ◽  
pp. 670-676 ◽  
Author(s):  
J. J. Jaeger ◽  
J. T. Sylvester ◽  
A. Cymerman ◽  
J. J. Berberich ◽  
J. C. Denniston ◽  
...  
Keyword(s):  
Pulmonary Edema ◽  
High Altitude ◽  
Transpulmonary Pressure ◽  
Fluid Volume ◽  
Pulmonary Mechanics ◽  
Volume Curve ◽  
Extravascular Fluid ◽  
Pressure Volume Curve ◽  
Transthoracic Electrical Impedance ◽  
Extravascular Fluid Volume

To determine if subclinical pulmonary edema occurs commonly at high altitude, 25 soldiers participated in two consecutive 72-h field exercises, the first at low altitude (200–875 m) and the second at high altitude (3,000–4,300 m). Various aspects of ventilatory function and pulmonary mechanics were measured at 0, 36, and 72 h of each exercise. Based on physical examination and chest radiographs there was no evidence of pulmonary edema at high altitude. There was, however, an immediate and sustained decrease in vital capacity and transthoracic electrical impedance as well as a clockwise rotation of the transpulmonary pressure-volume curve. In contrast, closing capacity and residual volume did not change immediately upon arrival at high altitude but did increase later during the exposure. These observations are consistent with an abrupt increase in thoracic intravascular fluid volume upon arrival at high altitude followed by a more gradual increase in extravascular fluid volume in the peribronchial spaces of dependent lung regions.

Series distribution of airway collapsibility in dogs

1981 ◽  
Vol 50 (2) ◽  
pp. 325-333 ◽  
Author(s):  
M. Nakamura ◽  
H. Sasaki ◽  
K. Sekizawa ◽  
M. Ishii ◽  
T. Takishima ◽  
...  
Keyword(s):  
Transpulmonary Pressure ◽  
Forced Expiration ◽  
Peripheral Airways ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Airway Collapsibility

We studied the series distribution of collapsibility in four different-sized airways in dogs. The trachea and the extrapulmonary main bronchi in situ were isolated from the rest of the lungs by glued beads of 6-12 mm OD. In excised dog lungs, the intrapulmonary large and small bronchi were isolated from the rest of the lung by glued beads of 1-9 mm OD. Pressure-volume relationships were measured directly in the trachea and in the extrapulmonary bronchi; those of the intrapulmonary bronchi were derived from orthogonal bronchograms. Airway collapsibility, defined as the slope of the pressure-volume curve, was found to increase in all airways as transpulmonary pressure (PL) decreased. At PL 30 cmH2O there was little difference of airway collapsibility among the different sized airways; but, as PL decreased, the peripheral airways became more collapsible than the central airways. It is concluded that the tissues surrounding the trachea provided as much or more stiffness than did the lung tissues that surrounded the intrapulmonary airways. The larger collapsibility in the peripheral airways. The larger collapsibility in the peripheral airways relative to that of the central airways at lower PL may account for the peripheral migration of the flow-limiting segment during forced expiration.

Xenon and nitrogen single-breath washout curves in patients with airway obstruction

1976 ◽  
Vol 41 (2) ◽  
pp. 185-190 ◽  
Author(s):  
M. Demedts ◽  
M. de Roo ◽  
J. Cosemans ◽  
L. Billiet ◽  
K. P. van de Woestijne
Keyword(s):  
Airway Obstruction ◽  
Chronic Obstructive Lung Disease ◽  
Chronic Obstructive ◽  
Closing Volume ◽  
Residual Volume ◽  
Time Constants ◽  
Single Breath ◽  
Volume Curve ◽  
Washout Curves ◽  
Severe Airway Obstruction

In patients with chronic obstructive lung disease, we determined single-breath N2 and 133 Xe washout curves, and regional distributions of volumes (Vr) and of 133Xe boluses inhaled at residual volume (VIRV). Patients suffering from emphysema with minimal airway obstruction demonstrated large closing volumes and apicobasal distribution gradients, apparently because of a steep pulmonary recoil pressure-volume curve. In one subject with basal small airway disease there was no vertical gradient in regional residual volume; closing volume was increased with the 133Xe technique but almost absent with the N2 technique. Patients with moderate-to-severe airway obstruction had upward-sloping alveolar plateaus without distinct phase IV, and small apicobasal differences in Vr and VIRV. The latter resulted probably from increased regional differences in time constants counteracting the influence of gravity. Finally, patients with severe airway obstruction and basal emphysema demonstrated a rising N2 but a descending 133Xe plateau; the gradient for VIRV was normal, and reversed for Vr. This pattern was attributed to nongravitational differences in time constants causing a first in-first out distribution.

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