Mechanism of reduced maximum expiratory flow in dogs with compensatory lung growth

1986 ◽  
Vol 60 (2) ◽  
pp. 441-448 ◽  
Author(s):  
H. W. Greville ◽  
M. E. Arnup ◽  
S. N. Mink ◽  
L. Oppenheimer ◽  
N. R. Anthonisen
Keyword(s):  
Control Flow ◽  
Sham Operation ◽  
Forced Expiration ◽  
Flow Limitation ◽  
Lung Growth ◽  
Lung Volumes ◽  
Flow Rates ◽  
Compensatory Lung Growth ◽  
Maximum Expiratory Flow ◽  
Expiratory Flow

We examined the mechanism of the reduced maximum expiratory flow rates (Vmax) in a dog model of postpneumonectomy compensatory lung growth. During forced expiration, a Pitot-static tube was used to locate the airway site of flow limitation, or choke point, and to measure dynamic intrabronchial pressures. The factors determining Vmax were calculated and the results analyzed in terms of the wave-speed theory of flow limitation. Measurements were made at multiple lung volumes and during ventilation both with air and with HeO2. Five of the puppies had undergone a left pneumonectomy at 10 wk of age, and 5 littermate controls had undergone a sham operation. All dogs were studied at 26 wk of age, at which time compensatory lung growth had occurred in the postpneumonectomy group. Vmax was markedly decreased in the postpneumonectomy group compared with control, averaging 42% of the control flow rates from 58 to 35% of the vital capacity (VC). At 23% of the VC, Vmax was 15% less than control. Choke points were more peripheral in the postpneumonectomy dogs compared with controls at all volumes. The total airway pressure was the same at the choke-point airway in the postpneumonectomy dogs as that in the same airway in the control dogs, suggesting that the airways of the postpneumonectomy dogs displayed different bronchial area-pressure behavior from the control dogs. Despite the decreased Vmax on both air and HeO2, the density dependence of flow was high in the postpneumonectomy dogs and the same as controls at all lung volumes examined.

Heterogeneity of maximal lobar emptying rates in dogs with compensatory lung growth

1989 ◽  
Vol 67 (3) ◽  
pp. 1164-1170 ◽  
Author(s):  
S. N. Mink ◽  
S. G. Holtby ◽  
D. J. Berenzanski ◽  
L. Oppenheimer ◽  
N. R. Anthonisen
Keyword(s):  
Vital Capacity ◽  
Sham Operation ◽  
Forced Expiration ◽  
Lung Growth ◽  
Lung Weight ◽  
Reduced Pressure ◽  
Lung Volumes ◽  
Maximum Expiratory Flow ◽  
Expiratory Flow ◽  
Left Pneumonectomy

Five dogs underwent left pneumonectomy at 10 wk of age, whereas four littermates underwent a sham operation. At 26 wk of age the postpneumonectomy dogs had total lung vital capacity (VC) and lung weight similar to controls, but maximum expiratory flow was reduced. Pressure capsules were glued to right lower (RLL) and right cardiac (RCL) lobes, and alveolar pressures (PA) were measured during forced expiration. In postpneumonectomy dogs RLL and RCL both emptied more slowly than in control dogs, and emptying was especially delayed in RCL, which underwent the most growth. When both lobes deflated together, PA in RCL and RLL were similar in control dogs, but in postpneumonectomy dogs PA in RCL exceeded that in RLL by approximately 3 cmH2O from 80 to 20% VC. Because the higher driving pressure in RCL compensated for the relatively high resistance of RCL, the pattern of lobar emptying was relatively uniform over these lung volumes. This result was compatible with interdependence of lobar maximum expiratory flows. In addition, at PA of 6–10 cmH2O in postpneumonectomy dogs, maximum emptying rates of RCL were less when RCL deflated alone than when RCL and RLL emptied together, again demonstrating interdependence of lobar maximum expiratory flow.

OBSTRUCTIVE DISEASE OF THE AIRWAYS IN CYSTIC FIBROSIS

PEDIATRICS ◽  
1968 ◽  
Vol 41 (3) ◽  
pp. 560-573
Author(s):  
Robert B. Mellins ◽  
O. Robert Levine ◽  
Roland H. Ingram ◽  
Alfred P. Fishman
Keyword(s):  
Cystic Fibrosis ◽  
Vital Capacity ◽  
Maximum Flow ◽  
Transpulmonary Pressure ◽  
Forced Expiration ◽  
Lung Volumes ◽  
Flow Rates ◽  
Maximum Expiratory Flow ◽  
Expiratory Flow ◽  
Expiratory Flow Rates

A study of the interrelationships of instantaneous air flow, lung volume, and transpulmonary pressure over the range of the vital capacity has demonstrated striking differences in the determinants of maximum expiratory flow in cystic fibrosis and asthma. At high lung volumes, maximum expiratory flow rates in asthma are limited by the mechanical characteristics of the lungs and airways, whereas in cystic fibrosis and in the normal they are dependent on effort. At lower lung volumes, maximum expiratory flow rates are relatively more reduced in cystic fibrosis than in asthma and pressures in excess of those required to produce maximum flow actually depress flow. Also, forced expiration is associated with a transient reversal in the slope of the single breath nitrogen curve in cystic fibrosis and not in asthma. From these studies it is concluded that: (1) airway obstruction is less uniform and involves larger airways in cystic fibrosis than in asthma, and (2) increased expiratory pressure is associated with collapse of some of the larger airways over most of the range of the vital capacity in cystic fibrosis. A major clinical implication of these studies is that the effectiveness of cough is impaired by large airway collapse in cystic fibrosis.

Flow-Volume Relationship at Low Lung Volumes in Healthy Term Newborn Infants

PEDIATRICS ◽  
1978 ◽  
Vol 61 (4) ◽  
pp. 636-640
Author(s):  
Saul M. Adler ◽  
Mary Ellen B. Wohl
Keyword(s):  
Newborn Infants ◽  
Chamber Pressure ◽  
Positive Pressure ◽  
Forced Expiration ◽  
Flow Volume ◽  
Convex Shape ◽  
Lung Volumes ◽  
Volume Relationship ◽  
Maximum Expiratory Flow ◽  
Expiratory Flow

To describe the maximum expiratory flow-volume relationship in newborn infants, we simulated forced expiration by transiently applying positive pressure in a chamber surrounding the infant's body. Maximum expiratory flows were reached at any given lung volume when increases in chamber pressure failed to produce increases in flow. Maximum expiratory flows were achieved in seven of nine healthy newborn infants at lung volumes equal to functional residual capacity (FRC) and in all infants at lung volumes below FRC. The volume expired below FRC (6.4 ml/kg) was roughly equivalent to previously calculated values of expiratory reserve volume in newborn infants (7 ml/kg). The maximum expiratory flow volume curves showed that the infants were able to increase expiratory flow rates well above those achieved during tidal breathing. The convex shape of the curves at low lung volumes is compatible with flow limitation occurring in peripheral airways.

Changes in regional emptying sequence need not change maximum expiratory flow

1986 ◽  
Vol 60 (6) ◽  
pp. 1834-1838 ◽  
Author(s):  
R. B. Filuk ◽  
N. R. Anthonisen
Keyword(s):  
Vital Capacity ◽  
Total Lung Capacity ◽  
Young Men ◽  
Forced Expiration ◽  
Flow Volume ◽  
Lung Volumes ◽  
Lung Capacity ◽  
Maximum Expiratory Flow ◽  
Expiratory Flow

Nine normal young men inhaled boluses of He at the onset of slow vital capacity (VC) inspirations. During the subsequent VC expirations, we measured expired flow, volume, and He concentrations. Expirations consisted of full or partial maximum expiratory flow-volume (MEFV) maneuvers. Full maneuvers were forced expirations from total lung capacity (TLC). Partial maneuvers were accomplished by expiring slowly from TLC to 70, 60, 50, and 40% VC and then initiating forced expiration. Expired He concentrations from full and partial maneuvers were compared with each other and with those resulting from slow expirations. At comparable volumes less than 50% VC, flow during partial and full MEFV maneuvers did not differ. Expired He concentrations were higher during partial maneuvers than during full ones; at the onset of partial maneuvers upper zone emptying predominated, whereas this was not the case at the same lung volumes during maneuvers initiated at TLC. We observed substantial differences in regional emptying sequence that did not influence maximum expiratory flow.

Breathing at low lung volumes and chest strapping: a comparison of lung mechanics

1981 ◽  
Vol 50 (3) ◽  
pp. 650-657 ◽  
Author(s):  
N. J. Douglas ◽  
G. B. Drummond ◽  
M. F. Sudlow
Keyword(s):  
Lung Volume ◽  
Maximum Flow ◽  
Normal Subjects ◽  
Lung Mechanics ◽  
Lung Volumes ◽  
Flow Rates ◽  
Recoil Pressure ◽  
Forced Expiratory Flow ◽  
Expiratory Flow ◽  
Expiratory Flow Rates

In six normal subjects forced expiratory flow rates increased progressively with increasing degrees of chest strapping. In nine normal subjects forced expiratory flow rates increased with the time spent breathing with expiratory reserve volume 0.5 liters above residual volume, the increase being significant by 30 s (P less than 0.01), and flow rates were still increasing at 2 min, the longest time the subjects could breathe at this lung volume. The increase in flow after low lung volume breathing (LLVB) was similar to that produced by strapping. The effect of LLVB was diminished by the inhalation of the atropinelike drug ipratropium. Quasistatic recoil pressures were higher following strapping and LLVB than on partial or maximal expiration, but the rise in recoil pressure was insufficient to account for all the observed increased in maximum flow. We suggest that the effects of chest strapping are due to LLVB and that both cause bronchodilatation.

scholarly journals Viscoelasticity of the trachea and its effects on flow limitation

2006 ◽  
Vol 100 (2) ◽  
pp. 384-389 ◽  
Author(s):  
Nikolai Aljuri ◽  
Jose G. Venegas ◽  
Lutz Freitag
Keyword(s):  
Wave Speed ◽  
Mathematical Representation ◽  
Forced Expiration ◽  
Flow Limitation ◽  
Time Dependency ◽  
Cross Sectional ◽  
Elastic Tubes ◽  
Forced Expiratory Flow ◽  
Expiratory Flow ◽  
The Relationship

To test the hypothesis that peak expiratory flow is determined by the wave-speed-limiting mechanism, we studied the time dependency of the trachea and its effects on flow limitation. For this purpose, we assessed the relationship between transmural pressure and cross-sectional area [the tube law (TL)] of six excised human tracheae under controlled conditions of static (no flow) and forced expiratory flow. We found that TLs of isolated human tracheae followed quite well the mathematical representation proposed by Shapiro (Shapiro AH. J Biomech Eng 99: 126–147, 1977) for elastic tubes. Furthermore, we found that the TL measured at the onset of forced expiratory flow was significantly stiffer than the static TL. As a result, the stiffer TL measured at the onset of forced expiratory flow predicted theoretical maximal expiratory flows far greater than those predicted by the more compliant static TL, which in all cases studied failed to explain peak expiratory flows measured at the onset of forced expiration. We conclude that the observed viscoelasticity of the tracheal walls can account for the measured differences between maximal and “supramaximal” expiratory flows seen at the onset of forced expiration.

Variability of the configuration of maximum expiratory flow-volume curves

1979 ◽  
Vol 46 (3) ◽  
pp. 565-570 ◽  
Author(s):  
Y. K. Tien ◽  
E. A. Elliott ◽  
J. Mead
Keyword(s):  
Normal Subjects ◽  
Flow Limitation ◽  
Residual Volume ◽  
Flow Volume ◽  
Maximum Difference ◽  
Slope Ratio ◽  
Computer Technique ◽  
Volume Increment ◽  
Maximum Expiratory Flow ◽  
Expiratory Flow

With a computer technique variability of the configuration of maximum expiratory flow-volume (MEFV) curves was studied in terms of slope ratio, SR. SR = dV/dV divided by V/V, where V is the instantaneous flow and V is the volume increment above residual volume.) Approximately four SR-V curves, each based on three to five smoothed and averaged MEFV curves, were derived for each of 20 normal subjects (aged 23–55 yr) on a single occasion, and again at least 1 wk later. Individual curves were largely reproducible, the maximum difference in SR at most volumes being 0.3–1 U, but frequently showed substantial yet reproducible fluctuations with volume. These corresponeded to hitherto unrecognized irregularities of maximum expiratory flow that may reflect sudden changes in the location of flow limitation.

Lung volumes after an increase in lung distension in pneumonectomized ferrets

1989 ◽  
Vol 67 (4) ◽  
pp. 1418-1421 ◽  
Author(s):  
J. T. McBride
Keyword(s):  
Lung Resection ◽  
Transpulmonary Pressure ◽  
Tissue Growth ◽  
Lung Growth ◽  
Lung Volumes ◽  
Compensatory Lung Growth ◽  
Rubber Balloon ◽  
Residual Capacity ◽  
The Right

To investigate the role of lung distension in compensatory lung growth, the right lung of each of 21 adult male ferrets was replaced with a silicone rubber balloon filled with mineral oil. Three to thirteen weeks after surgery, the oil was removed through a subcutaneous port. Lung volumes were measured serially until 3–6 wk after balloon deflation. With pneumonectomy the total lung capacity (TLC) decreased to less than 50% of the preoperative value and remained essentially unchanged while the balloon was inflated. At balloon deflation, TLC and vital capacity did not change immediately, whereas functional residual capacity increased by 44%, indicating a change of 2–3 cmH2O in end-expiratory transpulmonary pressure. TLC increased by 10% within 3 days and continued to increase over the subsequent 3–5 wk by a total of 25% over TLC at balloon deflation. There was little difference in this response between animals whose balloons were deflated 3 wk after surgery and those in which deflation was delayed up to 13 wk. After pneumonectomy in the adult ferret, the remaining lung increases in volume in response to an increase in lung distension even weeks or months after surgery. The extent to which this volume increase involves lung tissue growth or depends on previous lung resection is at present unknown. This model may be useful for studies of the mechanisms by which lung distension influences lung volume and compensatory lung growth.

Density-Dependence of Maximal Expiratory Flow Rates before and after Bronchodilators in Patients with Obstructive Airways Disease

1976 ◽  
Vol 51 (2) ◽  
pp. 133-139
Author(s):  
J. J. Wellman ◽  
E. R. McFadden ◽  
R. H. Ingram
Keyword(s):  
Density Dependence ◽  
Lung Volumes ◽  
Flow Rates ◽  
Maximal Expiratory Flow ◽  
Before And After ◽  
Group A ◽  
Obstructive Airways Disease ◽  
Expiratory Flow ◽  
Group B ◽  
Expiratory Flow Rates

1. Gas-density-dependence of maximal expiratory flow rates (V̇max), defined as the ratio of V̇max while breathing helium/oxygen (80:20) to V̇max. while breathing air at the same lung volume, was examined in relation to other measurements of airways obstruction in patients with obstructive airways disease before and after administration of bronchodilators. 2. Seventeen patients showed a 45% or greater increase in specific conductance(sGaw) after bronchodilator therapy (group A) and thirteen patients demonstrated a lesser response (group B). 3. Before the administration of bronchodilators, the degree of obstruction in the two groups was not different as measured by lung volumes, sGaw, forced expiratory volume in 1 s, and flow rates high in the vital capacity; yet the maximal mid-expiratory flow rate and the degree of density-dependence were significantly lower in group B. 4. After bronchodilators, both groups of patients showed significant improvements in sGaw flow rates and lung volumes. However, group A patients showed a significant increase in density-dependence whereas group B patients did not. 5. Increased density-dependence after bronchodilators in the group A patients was associated with an increase in the computed resistance of the upstream segment with air and a decrease in resistance with helium/oxygen. These changes could be explained by a more mouthward movement of equal pressure points, and therefore a further increase in the relative contribution of the larger density-dependent airways to limitation of flow. 6. The fact that density-dependence was not altered after bronchodilators in the group B patients suggests that the site of limitation of flow did not change appreciably. The shift in the pressure—flow curve for the upstream airways was such that the computed resistance of these airways fell. Thus it appears that the airways comprising the upstream segment were dilated.

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