Changes in regional lung impedance after intravenous histamine bolus in dogs: effects of lung volume

1995 ◽  
Vol 78 (3) ◽  
pp. 875-880 ◽  
Author(s):  
Z. Balassy ◽  
M. Mishima ◽  
J. H. Bates
Keyword(s):  
Lung Volume ◽  
Time Course ◽  
Lung Inflation ◽  
Lung Elastance ◽  
Airway Narrowing ◽  
Tracheal Pressure ◽  
Lung Resistance ◽  
Regional Lung ◽  
Before And After ◽  
Induced Changes

We measured the effect of lung volume on the time course of regional lung input impedance (ZA) after bolus intravenous administration of 2 mg of histamine in seven open-chest dogs using alveolar capsule oscillators. ZA (24–200 Hz) was obtained during apnea at constant lung volume every 2 s for 80 s at lung inflation pressures of 0.1, 0.2, 0.3, 0.5, 0.7, and 1.0 kPa. Local airway resistance (RA) and elastance of the local lung region were calculated by fitting a four-parameter model to the measured ZA. Total lung resistance and lung elastance were also calculated from tracheal pressure and flow measured during mechanical ventilation (0.3 Hz) just before and after each set of ZA measurements. We found the histamine-induced changes in both lung resistance and lung elastance to decrease with increasing lung volume. RA also showed a large negative dependency on lung volume, and the variation between different RA measurements became markedly increased as lung volume decreased. In contrast, local airway elastance was essentially unaffected by lung volume. These results support the idea that parenchymal tethering of the very distal airways impedes their narrowing during bronchoconstriction. They also indicate that reduced parenchymal tethering causes airway narrowing to become markedly more inhomogeneous.

Lung tissue distortion in response to methacholine in rats: effect of lung volume

1995 ◽  
Vol 79 (2) ◽  
pp. 533-538 ◽  
Author(s):  
M. Dolhnikoff ◽  
M. Dallaire ◽  
M. S. Ludwig
Keyword(s):  
Lung Volume ◽  
Freeze Substitution ◽  
Mechanically Ventilated ◽  
Airway Narrowing ◽  
Airway Lumen ◽  
Airway Constriction ◽  
Tracheal Pressure ◽  
Lung Resistance ◽  
Mean Linear Intercept ◽  
The Mean

We have previously shown that, after induced constriction, there is substantial distortion of the parenchymal tissues. In this study we investigated whether differences in parenchymal morphology occurred when the lung was constricted at different lung volumes. We measured tracheal pressure and calculated lung resistance in mechanically ventilated rats under control conditions and after aerosol administration of methacholine (256 mg/ml) at different positive end-expiratory pressures (PEEP = 7, 5, and 3 cmH2O). The lungs were frozen with liquid nitrogen at different PEEP levels and processed via freeze substitution. We measured airway constriction as the ratio of the airway lumen to the ideally relaxed area, alveolar size by measuring the mean linear intercept between alveolar walls, and tissue distortion as the standard deviation of the number of intercepts in the 40 fields sampled per lung. The increase in lung resistance was largest at PEEP = 3 cmH2O. Whereas airway constriction decreased and alveolar size increased at higher lung volume (PEEP = 7 cmH2O), tissue distortion did not change. These data suggest that parenchymal distortion after induced constriction was not attributable to airway narrowing and/or closure.

Methacholine-induced bronchoconstriction in dogs: effects of lung volume and O3 exposure

1988 ◽  
Vol 65 (6) ◽  
pp. 2679-2686 ◽  
Author(s):  
S. T. Kariya ◽  
S. A. Shore ◽  
W. A. Skornik ◽  
K. Anderson ◽  
R. H. Ingram ◽  
...  
Keyword(s):  
Lung Volume ◽  
Maximal Response ◽  
Maximal Effect ◽  
Response Curves ◽  
Lung Volumes ◽  
Before And After ◽  
Residual Capacity ◽  
Induced Changes ◽  
Conducting Airways ◽  
Concentration Response Curve

The maximal effect induced by methacholine (MCh) aerosols on pulmonary resistance (RL), and the effects of altering lung volume and O3 exposure on these induced changes in RL, was studied in five anesthetized and paralyzed dogs. RL was measured at functional residual capacity (FRC), and lung volumes above and below FRC, after exposure to MCh aerosols generated from solutions of 0.1-300 mg MCh/ml. The relative site of response was examined by magnifying parenchymal [RL with large tidal volume (VT) at fast frequency (RLLS)] or airway effects [RL with small VT at fast frequency (RLSF)]. Measurements were performed on dogs before and after 2 h of exposure to 3 ppm O3. MCh concentration-response curves for both RLLS and RLSF were sigmoid shaped. Alterations in mean lung volume did not alter RLLS; however, RLSF was larger below FRC than at higher lung volumes. Although O3 exposure resulted in small leftward shifts of the concentration-response curve for RLLS, the airway dominated index of RL (RLSF) was not altered by O3 exposure, nor was the maximal response using either index of RL. These data suggest O3 exposure does not affect MCh responses in conducting airways; rather, it affects responses of peripheral contractile elements to MCh, without changing their maximal response.

Pressure outside the extrapulmonary airway in dogs

1978 ◽  
Vol 45 (3) ◽  
pp. 437-441 ◽  
Author(s):  
S. G. Spiro ◽  
B. H. Culver ◽  
J. Butler
Keyword(s):  
Lung Volume ◽  
Standing Position ◽  
Pleural Pressure ◽  
Positive Pressure ◽  
Anterior Surface ◽  
Lung Inflation ◽  
Airway Narrowing ◽  
Thin Fluid ◽  
Airway Pressures ◽  
Anesthetized Dogs

We have measured the static and dynamic transmural pressures of extrapulmonary airways during positive pressure lung inflation in anesthetized dogs suspended in the standing position. Thin, fluid-filled catheters measured pressures within and on the anterior surface of the airways in the mediastinum and neck. The change from mediastinal to cervical static extra-airway pressures (Pea) was not abrupt but occurred through the thoracic outlet and the root of the neck. The static Pea in the mediastinum was more positive than pleural pressure when lung volume was increased with positive pressures. During forced deflation equal pressure points (EPP) were in labor bronchi from which airway narrowing extended towards the mouth. Under these conditions, the dynamic mediastinal Pea mouthward of the EPP remained close to pleural pressures even at high volumes. This suggested that forces of restitution generated in the surrounding tissues by the narrowing of the airways did have a small effect in reducing the pressure affecting their anterior surface.

Temporal dynamics of pulmonary response to intravenous histamine in dogs: effects of dose and lung volume

1994 ◽  
Vol 76 (2) ◽  
pp. 616-626 ◽  
Author(s):  
J. H. Bates ◽  
A. M. Lauzon ◽  
G. S. Dechman ◽  
G. N. Maksym ◽  
T. F. Schuessler
Keyword(s):  
Time Course ◽  
Temporal Dynamics ◽  
Oscillation Period ◽  
Recursive Least Squares ◽  
Positive End Expiratory Pressure ◽  
Elastic Recoil ◽  
Ventilation Inhomogeneity ◽  
Tracheal Pressure ◽  
Lung Resistance ◽  
Time Courses

We measured tracheal pressure (Ptr) and tracheal flow (V) in open-chest anesthetized paralyzed dogs. The lungs were maintained at a fixed volume (initial positive end-expiratory pressure 0.5 kPa) for 80 s while small-amplitude oscillations in V at 1 and 6 Hz were applied simultaneously at the tracheal opening. A bolus of histamine was given intravenously at the start of the oscillation period. The time course of lung elastic recoil pressure (Pel) was obtained by passing a running average over Ptr to smooth out its oscillations. The oscillations themselves were separated into their 1- and 6-Hz components, as were those in V. By fitting models to the 1- and 6-Hz components of Ptr and V by recursive least squares, we obtained time courses of lung resistance at 6 Hz (RL6), dynamic lung elastance at 1 Hz (EL1), and the difference between dynamic lung resistance at 1 and 6 Hz (RL1-RL6). In four dogs we studied the effects of histamine doses of 0.05, 1.0, and 20 mg. We found that Pel increased quickly and plateaued, RL6 continued to increase throughout the oscillation period, and EL1 exhibited features of both Pel and RL6. Furthermore, the ratio of RL1-RL6 to EL1 was qualitatively similar in time course to Pel. We explain these varied time courses in terms of the development of regional ventilation inhomogeneity throughout the lung as the reaction to histamine develops. In four dogs we also studied the effects of reducing the initial positive end-expiratory pressure by 0.25 kPa and found that the changes in RL6, EL1, and RL1-RL6 were greatly magnified, presumably because of the reduced forces of parenchymal interdependence.

The Interpretation of Different Measurements of Airways Obstruction in the Presence of Lung Volume Changes in Bronchial Asthma

1978 ◽  
Vol 54 (3) ◽  
pp. 313-321
Author(s):  
K. B. Saunders ◽  
M. Rudolf
Keyword(s):  
Lung Volume ◽  
Time Course ◽  
Forced Expiratory Volume ◽  
Specific Conductance ◽  
Volume Changes ◽  
Lung Volumes ◽  
Bronchodilator Response ◽  
Before And After ◽  
Residual Capacity ◽  
Airways Resistance

1. We measured changes in peak expiratory flow rate (PEFR), forced expiratory volume in 1 s (FEV1·0), airways resistance (Raw), specific conductance (sGaw), residual volume (RV), functional residual capacity (FRC) and total lung capacity (TLC) in 44 patients with asthma. 2. When asthma was induced by exercise in five patients there were large changes in volumes, but these did not obscure changes in PEFR, which adequately defined the time course of the response. 3. In 70 comparisons before and after inhalation of bronchodilator drug in 33 asthmatic subjects, the responses were classified by the size of the change in lung volumes, which showed a concordant improvement, or no change, in 61 comparisons. Despite these lung volume changes, measurement of both PEFR and FEV1·0, would have detected a bronchodilator response in all but two cases. 4. In 81 comparisons in 23 subjects over time intervals varying from 1 day to 11 months, lung volumes changed in concordance with PEFR and FEV1·0 in 59. In eight of these comparisons, measurement of lung volumes would have altered our interpretation of the changes in PEFR and FEV1·0. 5. In the same 81 comparisons changes in airways resistance were concordant with changes in PEFR and FEV1·0 on 44 occasions, with minor discordant changes in 19. We could not explain the remaining 18 cases showing major discordance between these two types of measurement of airway calibre. 6. We conclude that both FEV1·0, and PEFR should be used for detection of a bronchodilator response, and that measurement of lung volumes will rarely contribute to the interpretation. Over longer periods, lung volumes should be measured if possible. We found no practical use for routine measurement of airways resistance in patients with asthma.

Effects of lung volume, volume history, and methacholine on lung tissue viscance

1989 ◽  
Vol 66 (2) ◽  
pp. 977-982 ◽  
Author(s):  
S. T. Kariya ◽  
L. M. Thompson ◽  
E. P. Ingenito ◽  
R. H. Ingram
Keyword(s):  
Lung Tissue ◽  
Volume Change ◽  
Lung Volume ◽  
Airway Resistance ◽  
Base Line ◽  
Lung Volumes ◽  
Lung Resistance ◽  
Before And After ◽  
The Subject ◽  
Volume History

We examined the effects of lung volume change and volume history on lung resistance (RL) and its components before and during induced constriction. Eleven subjects, including three current and four former asthmatics, were studied. RL, airway resistance (Raw), and, by subtraction, tissue viscance (Vtis) were measured at different lung volumes before and after a deep inhalation and were repeated after methacholine (MCh) aerosols up to maximal levels of constriction. Vtis, which average 9% of RL at base line, was unchanged by MCh and was not changed after deep inhalation but increased directly with lung volume. MCh aerosols induced constriction by increasing Raw, which was reversed by deep inhalation in inverse proportion to responsiveness. such that the more responsive subjects reversed less after a deep breath. Responsiveness correlated directly with the degree of maximal constriction, as more responsive subjects constricted to a greater degree. These results indicate that in humans Vtis comprises a small fraction of overall RL, which is clearly volume-dependent but unchanged by MCh-induced constriction and unrelated to the degree of responsiveness of the subject.

scholarly journals Mechanical properties of lung parenchyma during bronchoconstriction

1999 ◽  
Vol 86 (2) ◽  
pp. 496-502 ◽  
Author(s):  
Mitsushi Okazawa ◽  
Yulia D’Yachkova ◽  
Peter D. Paré
Keyword(s):  
Mechanical Properties ◽  
Lung Volume ◽  
Indentation Test ◽  
Lung Parenchyma ◽  
Shear Moduli ◽  
Slow Oscillations ◽  
Airway Narrowing ◽  
Major Mechanism ◽  
Volume Ventilation ◽  
Before And After

Interdependence between airways and the lung parenchyma is thought to be a major mechanism preventing excessive airway narrowing during bronchoconstriction. Because the elastance of the lung increases during bronchoconstriction, the lung’s tethering force could also increase, further attenuating bronchoconstriction. We hypothesized that the bulk (κ) and shear moduli (μ) of the lung increase similarly during bronchoconstriction. To test this hypothesis, we excised rabbit lungs and measured the lung volume, pulmonary elastance, κ, and μ at transpulmonary pressures of 4, 6, 8, 12, and 16 cmH2O using pressure-volume curves, slow oscillations of the lung, and an indentation test. Bronchoconstriction was induced by nebulizing carbachol by using small tidal-volume ventilation to prevent hyperinflation. The measurement of κ and μ was repeated after carbachol treatment. After carbachol treatment, the increase in κ was significantly greater than that in μ. The estimated value for μ was ∼0.5 × transpulmonary pressureboth before and after carbachol treatment. These data suggest that the tethering effect of the lung parenchyma, which serves to attenuate bronchoconstriction, is not significantly increased during carbachol administration unless there is hyperinflation.

Regional and temporal variation in canine peripheral lung responses to dry air

1989 ◽  
Vol 67 (5) ◽  
pp. 1727-1733 ◽  
Author(s):  
A. N. Freed
Keyword(s):  
Base Line ◽  
Airway Narrowing ◽  
Dry Air ◽  
Percent Change ◽  
Peripheral Lung ◽  
Lung Resistance ◽  
Before And After ◽  
Lung Periphery ◽  
Resting Tone ◽  
Collateral System

Variation in dry airflow-induced broncho-constriction (AIB) in the canine lung periphery was examined using a wedged bronchoscope technique. Collateral system resistance (Rcs) was measured before and after dry-air challenge. Base-line Rcs was similar throughout the lung periphery, between dogs, and over time. Increasing base-line Rcs was correlated with increasing maximum Rcs 5 min postchallenge (Rcs5), increasing change in Rcs (dRcs5), and decreasing percent change in Rcs above base line (%Rcs5). In contrast to repeated challenge in which base-line Rcs was similar, the magnitude of AIB associated with consecutive challenges with unequal base lines depended on the parameter used to evaluate the response (i.e., Rcs5, dRcs5, or %Rcs5). Peripheral lung resistance then increased to a stimulus specific maximum regardless of base-line Rcs, although data expressed as %Rcs5 or dRcs5 may obscure this observation. Although a change in peripheral lung resistance does not necessarily imply airway narrowing, it is consistent with the idea that changes in Rcs are independent of the collateral system's resting tone.

Effect of lung volume on collateral ventilation in the dog

1980 ◽  
Vol 49 (1) ◽  
pp. 9-15 ◽  
Author(s):  
J. Kaplan ◽  
R. C. Koehler ◽  
P. B. Terry ◽  
H. A. Menkes ◽  
R. J. Traystman
Keyword(s):  
Lung Volume ◽  
Transpulmonary Pressure ◽  
Relative Increase ◽  
Small Airways ◽  
Lung Inflation ◽  
Before And After ◽  
Collateral Pathways ◽  
Flow Through ◽  
Collateral Ventilation

We studied the effect of lung volume on resistance through collateral pathways (Rcoll) and small airways (Rsaw) before and after the injection of methacholine into obstructed segments of intact dogs. Before methacholine, Rcoll decreased 15.0 ± 4.9 (SE)% per cmH2O increase in transpulmonary pressure (Ptp) and Rsaw decreased 5.1 ± 7.0 (SE)% per cmH2O increase in Ptp. Following methacholine, lung inflation resulted in similar decreases in Rcoll and Rsaw. The fall in Rcoll was significantly greater than the fall in Rsaw. When pressure in an obstructed segment (Ps) was increased with constant Ptp (nonhomogeneous inflation), Rcoll fell approximately half as much for each cmH2O increase in pressure compared to when Ptp was increased (homogeneous inflation). We conclude 1) that increases in lung volume have small effects on Rsaw so that there is a relative increase in flow through collateral channels serving obstructed poritons of lung and 2) that Rcoll is a function of the size of the obstructed segment that increases more under homogeneous than nonhomogeneous conditions.

Heart-lung interactions determined by electron beam X-ray CT in laterally recumbent rabbits

1995 ◽  
Vol 78 (2) ◽  
pp. 417-427 ◽  
Author(s):  
L. E. Olson ◽  
E. A. Hoffman
Keyword(s):  
Electron Beam ◽  
Lung Volume ◽  
Lateral Position ◽  
Lung Inflation ◽  
X Ray ◽  
Air Content ◽  
Gravitational Gradients ◽  
Tracheal Pressure ◽  
The Right ◽  
Lateral Recumbency

Electron beam X-ray computed tomography (CT) was used to measure lung air content and its distribution within the lung as well as lung shape and heart position in rabbits in right and left lateral recumbency. Sham-operated control (S) rabbits and left-pneumonectomized rabbits with wax plombage were studied at functional residual capacity (FRC) and total lung capacity. Results were obtained for both lungs and for the right lung only of S rabbits. FRC of both lungs and the right lung only of the S rabbits and of the remaining right lung of the pneumonectomized rabbits was smaller in rabbits in right lateral recumbency than in those in left lateral recumbency. The reduction in right lung volume at FRC was accompanied by an overall reduction in lung size, although the lung shape remained similar, and was accompanied by movement of the heart centroid toward the dependent chest and spine. Application of a positive tracheal pressure of 25 cmH2O increased lung volume and reduced the dependency of lung volume and shape on posture. Lung inflation in the right lateral position was accompanied by movement of the heart centroid away from the dependent chest and spine. Gravitational gradients in regional air content did not differ between the cranial half of the lung, which was in contact with the heart, and the caudal half of the right lung, which was not in contact with the heart. Likewise, the cephalocaudal gradient in regional air content was similar when the right lung was dependent and nondependent. The location of the heart in the cranial half of the thorax does not appear to induce differences in regional air content between the cranial and caudal lung halves.

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