Density dependence of maximal flow is lung volume dependent during bronchoconstriction

1987 ◽  
Vol 62 (2) ◽  
pp. 691-705 ◽  
Author(s):  
H. W. Greville ◽  
M. E. Arnup ◽  
S. N. Mink
Keyword(s):  
Airway Obstruction ◽  
Density Dependence ◽  
Lung Volume ◽  
Wave Speed ◽  
Airflow Obstruction ◽  
Phosphate Solution ◽  
Flow Limitation ◽  
Peripheral Airway ◽  
Maximum Expiratory Flow ◽  
Expiratory Flow

We examined the changes in maximum expiratory flow (Vmax) and the density dependence of maximum expiratory flow (delta Vmax) during histamine-induced bronchoconstriction in dogs. Histamine acid phosphate solution was nebulized into the airways of six dogs to produce predominantly peripheral airway obstruction. Vmax air, Vmax with the dogs breathing 80% He-20% O2 (delta Vmax), and airway sites of flow limitation (choke points) were examined at four lung volumes (VL), which ranged from 51 to 23% of the control vital capacity (VC). The findings were interpreted in terms of the wave-speed theory of flow limitation. At all VL, Vmax air decreased during bronchoconstriction by approximately 30% compared with the control value. Resistances peripheral to a 0.3-cm-diam airway were increased about threefold with histamine, whereas resistances between 0.6-cm-diam bronchi and main-stem bronchi increased just slightly. Airway diameters were measured in the air-dried lung at 20 cmH2O transpulmonary pressure. Our results showed that only at 44% VC did delta Vmax decrease in all experiments after histamine to indicate peripheral obstruction (mean: 68.5 to 45%). At 23% VC, delta Vmax increased slightly, from 22 to 28%. At 23 and 36% VC, substantial differences in the wave-speed variables between air and HeO2 were present before bronchoconstriction, so that delta Vmax was low in some dogs, although peripheral airway obstruction was not evident. When bronchoconstriction was produced, delta Vmax at 23% VC could not be decreased further and even increased in four of six dogs. Thus changes in delta Vmax at given lung volume may not reflect the predominant site of airflow obstruction during bronchoconstriction.

Mechanisms of increased maximum expiratory flow during HeO2 breathing in dogs

1979 ◽  
Vol 47 (3) ◽  
pp. 490-502 ◽  
Author(s):  
S. Mink ◽  
M. Ziesmann ◽  
L. D. Wood
Keyword(s):  
Density Dependence ◽  
Wave Speed ◽  
Flow Limitation ◽  
Elastic Recoil ◽  
Expiratory Flow Limitation ◽  
Pressure Losses ◽  
Peripheral Airways ◽  
Catheter Technique ◽  
Maximum Expiratory Flow ◽  
Expiratory Flow

We used the retrograde-catheter technique to investigate the effect of a helium-oxygen gas mixture (HeO2) on resistance to maximum expiratory flow (Vmax) in airways subsegments between alveoli and the equal pressure point (EPP), and between EPP and the flow-limiting segment (FLS). FLS were found at the same site in main-stem bronchi on both air and HeO2 in most dogs studied. Static elastic recoil pressure (Pel = 7 +/- 1 cmH2O) and the lateral pressure at FLS (Ptm' = 11 +/- cmH2O) were not different on the two gases, and delta Vmax averaged 33 +/- 12%. EPP were located on HeO2 in segmental bronchi (7 +/- 2 mm ID), and EPP on air were always located more downstream. There was no density dependence of resistance between alveoli and EPP on HeO2, and delta Vmax was due to the marked density dependence of the pressure losses of convective acceleration in the short airway segment between EPP HeO2 and FLS. Assuming that FLS is the “choke point,” these findings are consistent with wave-speed theory of flow limitation modified to account for viscous pressure losses in peripheral airways. These results and conclusions question previous interpretations of delta Vmax as an index of peripheral airways obstruction, and demonstrate the utility of wave-speed theory in explaining complicated mechanisms of expiratory flow limitation.

Expiratory flow limitation and regulation of end-expiratory lung volume during exercise

1993 ◽  
Vol 74 (5) ◽  
pp. 2552-2558 ◽  
Author(s):  
R. Pellegrino ◽  
V. Brusasco ◽  
J. R. Rodarte ◽  
T. G. Babb
Keyword(s):  
Lung Volume ◽  
Breathing Pattern ◽  
Airflow Obstruction ◽  
Forced Expiratory Volume ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Reflex Mechanism ◽  
Forced Expiratory Flow ◽  
Expiratory Flow ◽  
The Impact

To investigate the impact of expiratory flow limitation (FL) on breathing pattern and end-expiratory lung volume (EELV), we imposed a small expiratory threshold load for a few breaths during exercise in nine volunteers (29–62 yr): six were healthy and three had mild-to-moderate airflow obstruction (67–71% predicted forced expiratory volume in 1 s). Six subjects showed evidence of FL, i.e., tidal expiratory flow impinging on maximal forced expiratory flow, at one or more exercise levels. Whenever an expiratory threshold load was imposed, mean expiratory flow decreased (P < 0.02) in association with an increased expiratory time (TE; P < 0.05). When the load was imposed during non-FL conditions, TE increased less than expiratory flow decreased and EELV tended to increase. In contrast, during FL, with the load, TE increased more than expiratory flow decreased, subjects did not achieve maximal expiratory flow until a lower volume, and EELV decreased (P < 0.001). Under both FL and no-FL conditions, unloading reversed the changes associated with loading. These data indicate that the increase in EELV during exercise is linked to the occurrence of FL. We suggest that compression of airways downstream from the flow-limiting segment may elicit a reflex mechanism that influences breathing pattern by terminating expiration prematurely, thus increasing EELV.

Forced expiration and HeO2 response in canine peripheral airway obstruction

1985 ◽  
Vol 58 (6) ◽  
pp. 1788-1801 ◽  
Author(s):  
C. Jadue ◽  
H. Greville ◽  
J. J. Coalson ◽  
S. N. Mink
Keyword(s):  
Airway Obstruction ◽  
Wave Speed ◽  
Vital Capacity ◽  
Gas Mixtures ◽  
Relative Reduction ◽  
Forced Expiration ◽  
Flow Limitation ◽  
Measuring Device ◽  
Peripheral Airway ◽  
Group B

We examined the effect of peripheral airway obstruction on parameters of maximum expiratory flow (Vmax) in a canine model of bronchiolitis obliterans (B). B was produced by the repeated intrabronchial instillations of a 1% nitric acid solution in seven dogs (group B). In seven control dogs (group C), a normal saline solution was used. During forced vital capacity deflation, Vmax on air, the relative increase in Vmax on 80% He-20% O2 (delta Vmax), and airway sites of flow limitation “choke points” (CP) were determined at multiple lung volumes (VL). The findings were interpreted in terms of the wave-speed theory of flow limitation. Wave-speed parameters were identified with a pressure-measuring device positioned in the airway. Compared with the findings for group C, Vmax decreased substantially at the lower VL (less than 50% vital capacity) in group B, whereas there were no changes in delta Vmax at any VL. CP were identified in central airways in both groups but were slightly more upstream in group B. Our analysis indicated that the reduction in Vmax in group B was due to an increase in upstream frictional pressure losses (Pfr) that caused a relative reduction in the pressure head, so that choking occurred in slightly upstream airways. delta Vmax did not change in group B because with CP identified in central airways, Pfr were density dependent, and significant differences in head loss on the two gas mixtures did not occur. Choking therefore occurred with similar wave-speed variables on the two gas mixtures, and delta Vmax was maintained.

Insensitivity of maximum expiratory flow to bronchodilation in normal dogs

1990 ◽  
Vol 68 (5) ◽  
pp. 2006-2012 ◽  
Author(s):  
J. Eng ◽  
A. Gomez ◽  
S. Mink
Keyword(s):  
Wave Speed ◽  
Vital Capacity ◽  
Lower Lobe ◽  
Pressure Head ◽  
Complex Interaction ◽  
Base Line ◽  
Flow Limitation ◽  
Maximum Expiratory Flow ◽  
Expiratory Flow ◽  
The Right

We examined the effects of the inhaled parasympatholytic agent atropine and the sympathomimetic agent salbutamol on partitioned frictional pressure (Pfr) losses to the site of flow limitation (choke point, CP) in dogs to see how changes brought about by these agents would affect maximum expiratory flow (Vmax) and response to breathing 80% He-20% O2 (delta Vmax) in terms of wave-speed theory of flow limitation. In open-chest dogs, a Pitot-static tube was advanced down the right lower lobe to locate CP, to determine CP lateral and end-on pressures (PE), and to partition the airway into peripheral (alveoli to sublobar) and central (sublobar to CP) segments. Measurements were obtained at approximately 50% vital capacity. After inhalation, CP locations were unchanged with both bronchodilating agents. After atropine inhalation, Pfr central was decreased by one-half compared with base line. Despite the decrease in Pfr central, however, Vmax failed to increase after atropine because of altered bronchial area pressure (BAP) behavior at the CP site. After salbutamol inhalation, Pfr peripheral was reduced by about one-half compared with base line. However, Vmax failed to increase, because this reduction was too small to significantly increase the CP pressure head (i.e., PE). delta Vmax was also insensitive to these agents. Our results show mechanisms by which small changes in Pfr, as well as the complex interaction of changes in Pfr and BAP, may limit the use of Vmax in detecting bronchodilation at different airway sites.

Flow-Volume Curves in Infants with Lung Disease

PEDIATRICS ◽  
1983 ◽  
Vol 72 (4) ◽  
pp. 517-522
Author(s):  
S. Godfrey ◽  
E. Bar-Yishay ◽  
I. Arad ◽  
L. I. Landau ◽  
L. M. Taussig
Keyword(s):  
Lung Disease ◽  
Airway Obstruction ◽  
Lung Volume ◽  
Airway Resistance ◽  
Whole Body ◽  
Small Airways ◽  
Forced Expiration ◽  
Flow Volume ◽  
Complete Evaluation ◽  
Expiratory Flow

Partial expiratory flow-volume maneuvers have been performed on nine occasions on six infants with a variety of pulmonary problems using a new tech nique for thoracic compression. The infants were placed within an inflatable bag that was, itself, within a canvas bag. By sudden controlled inflation of the inner bag at end inspiration, partial expiratory flow-volume curves were generated and recorded by means of a face mask and pneumotachograph. By comparing these flow results with those airway resistance and lung volume measurements obtained from the infants in whole body plethysmography and by noting the effect of inhaling a helium/oxygen gas mixture, it was possible to partition the airway obstruction between large and small airways. The presence of small airway obstruction was noted in the absence of changes in airway resistance or lung volume in several instances. A complete evaluation of airway function should include this test of forced expiration for greater understanding and treatment of lung disease in infancy.

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.

Expiratory flow limitation during exercise in prepubescent boys and girls: prevalence and implications

2010 ◽  
Vol 108 (5) ◽  
pp. 1267-1274 ◽  
Author(s):  
Katherine E. Swain ◽  
Sara K. Rosenkranz ◽  
Bethany Beckman ◽  
Craig A. Harms
Keyword(s):  
Body Composition ◽  
Oxygen Saturation ◽  
Tidal Volume ◽  
Lean Body Mass ◽  
Lung Volume ◽  
Arterial Oxygen Saturation ◽  
Arterial Oxygen ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Expiratory Flow

The purpose of this study was to compare the prevalence and implications of expiratory flow limitation (EFL) during exercise in boys and girls. Forty healthy, prepubescent boys (B; n = 20) and girls (G; n = 20) were tested. Subjects completed pulmonary function tests and an incremental cycle maximal oxygen uptake (V̇o2max) test. EFL was recorded at the end of each exercise stage using the % tidal volume overlap method. Ventilatory and metabolic data were recorded throughout exercise. Arterial oxygen saturation (SpO2) was determined via pulse oximetry. Body composition was determined using dual-energy X-ray absorptiometry. There were no differences ( P > 0.05) in height, weight, or body composition between boys and girls. At rest, boys had significantly higher lung volumes (total lung capacity, B = 2.6 ± 0.5 liters, G = 2.1 ± 0.5 liters) and peak expiratory flow rates (B = 3.6 ± 0.6 l/s; G = 1.6 ± 0.3 l/s). Boys also had significantly higher V̇o2max (B = 46.9 ± 5.9 ml·kg lean body mass−1·min−1, G = 41.7 ± 6.6 ml·kg lean body mass−1·min−1) and maximal ventilation (B = 49.8 ± 8.8 l/min, G = 41.2 ± 8.3 l/min) compared with girls. There were no sex differences ( P > 0.05) at V̇o2max in VE /Vco2, end-tidal Pco2, heart rate, respiratory exchange ratio, or SpO2. The prevalence (B = 19/20 vs. G = 18/20) and severity (B = 58 ± 7% vs. G = 43 ± 8% tidal volume) of EFL was not significantly different in boys compared with girls at V̇o2max. A significant relationship existed between % EFL at V̇o2max and the change in end-expiratory lung volume from rest to maximal exercise in boys ( r = 0.77) and girls ( r = 0.75). In summary, our data suggests that EFL is highly and equally prevalent in prepubescent boys and girls during heavy exercise, which led to an increased end-expiratory lung volume but not to decreases in arterial oxygen saturation.

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.

Influence of airway geometry on expiratory flow limitation and density dependence

1983 ◽  
Vol 52 (1) ◽  
pp. 113-123 ◽  
Author(s):  
Ronald J. Knudson ◽  
Robert C. Schroter ◽  
Dwyn E. Knudson ◽  
Stuart Sugihara
Keyword(s):  
Density Dependence ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Expiratory Flow

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.

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