Influence of antigen challenge on density dependence of maximal expiratory flow and nitrogen washout curves in extrinsic bronchial asthma

The effect of carbachol-induced central bronchoconstriction on density dependence of maximal expiratory flow (MEF) was assessed in five dogs. MEFs were measured on air and an 80% He-20% O2 mixture before and after local application of carbachol to the trachea. Airway pressures were measured using a pitot-static probe, from which central airway areas were estimated. At lower concentrations of carbachol the flow-limiting site remained in the trachea over most of the vital capacity (VC), and tracheal area and compliance decreased in all five dogs. In four dogs, decreases in choke point area predominated and produced decreases in flows. In one dog the increase in airway “stiffness” apparently offset the fall in area to account for an increase in MEF. Density dependence measured as the ratio of MEF on HeO2 to MEF on air at 50% of VC increased in all five dogs. Increases in density dependence appeared to be related to increases in airway stiffness at the choke point rather than decreases in gas-related airway pressure differences. Lower concentrations produced a localized decrease in tracheal area and extended the plateau of the flow-volume curve to lower lung volumes. Higher concentrations caused further reductions in tracheal area and greater longitudinal extension of bronchoconstriction, resulting in upstream movement of the site of flow limitation at higher lung volumes. Density dependence increased if the flow-limiting sites remained in the trachea at mid-VC but fell if the flow-limiting site had moved upstream by that volume.

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Parenteral vs. inhaled atropine: density dependence of maximal expiratory flow

Journal of Applied Physiology ◽

10.1152/jappl.1982.53.2.392 ◽

1982 ◽

Vol 53 (2) ◽

pp. 392-396 ◽

Cited By ~ 14

Author(s):

J. W. Weiss ◽

E. R. McFadden ◽

R. H. Ingram

Keyword(s):

Density Dependence ◽

Vital Capacity ◽

Human Subjects ◽

Atropine Sulfate ◽

Parenteral Administration ◽

Elastic Recoil ◽

Maximal Expiratory Flow ◽

Parenteral Dose ◽

Before And After ◽

Expiratory Flow

Using forced vital capacity maneuvers, we measured maximal expiratory flow rates (Vmax) and static elastic recoil pressures of the lung [Pst(L)] using quasi-static maneuvers in normal nonsmoking human subjects who were breathing air and after a washing of 80% helium-20% oxygen before and after both inhaled and intravenously administered atropine sulfate. By both routes there were equivalent increases in Vmaxair but different effects on density dependence (DD) of Vmax (DD = ratio of VmaxHeO2 to Vmaxair) and on Pst(L). At 30% of vital capacity, DD decreased from an average of 1.47 to 1.32 (P less than 0.01, paired t test) after inhaled drug and did not change after parenteral administration [1.44 vs. 1.48 (P greater than 0.2)]. After inhalation Pst(L) did not change, but after parenteral administration Pst(L) significantly decreased. We interpret these findings to indicate a predominantly large-airway effect with the inhalation route and a more uniform dilatation after the parenteral dose. These results contrast with beta-adrenergic dilatation following which small-airway effects predominate regardless of route of administration.

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Effect of Smoking a Cigarette on the Density Dependence of Maximal Expiratory Flow

Respiration ◽

10.1159/000194492 ◽

1982 ◽

Vol 43 (4) ◽

pp. 258-262 ◽

Cited By ~ 3

Author(s):

Angelo M. Taveira Da Silva ◽

Paul Hamosh

Keyword(s):

Density Dependence ◽

Maximal Expiratory Flow ◽

Expiratory Flow

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

Clinical Science ◽

10.1042/cs0510133 ◽

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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Bronchodilatation, lung recoil, and density dependence of maximal expiratory flow

Journal of Applied Physiology ◽

10.1152/jappl.1982.52.4.874 ◽

1982 ◽

Vol 52 (4) ◽

pp. 874-878 ◽

Cited By ~ 4

Author(s):

J. W. Weiss ◽

E. R. McFadden ◽

R. H. Ingram

Keyword(s):

Density Dependence ◽

Vital Capacity ◽

Human Subjects ◽

Beta Agonist ◽

Elastic Recoil ◽

Maximal Expiratory Flow ◽

Before And After ◽

Normal Human ◽

Expiratory Flow ◽

Expiratory Flow Rates

Using normal human subjects we have measured maximal expiratory flow rates with air (Vmaxair) and after a washin of 80% He-20% O2 (VmaxHeO2) and static elastic recoil pressures of the lung [Pst(L)] both before and after administration of a beta-agonist, terbutaline. The effects of inhaled drug were compared with those of the subcutaneously administered agent, each given in doses to produce maximal bronchodilatation as assessed by increases in Vmaxair in the mid-vital capacity. Although there was a significant yet modest decrease in Pst(L) only after injection of the agent, density dependence (DD), assessed as the ratio of VmaxHeO2 to Vmaxair, increased significantly and comparably after either route of administration. A modest decrease in Pst(L), therefore, did not affect the changes in DD.

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Density-Dependence of Maximal Expiratory Flow and Its Correlation with Small Airway Disease in Smokers

American Review of Respiratory Disease ◽

10.1164/arrd.1985.131.4.521 ◽

1985 ◽

Vol 131 (4) ◽

pp. 521-526 ◽

Cited By ~ 10

Author(s):

P. D. Paré ◽

L. A. Brooks ◽

C. A. Coppin ◽

J. L. Wright ◽

S. Kennedy ◽

...

Keyword(s):

Density Dependence ◽

Airway Disease ◽

Small Airway ◽

Small Airway Disease ◽

Maximal Expiratory Flow ◽

Expiratory Flow

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Concave Pattern of a Maximal Expiratory Flow-Volume Curve: A Sign of Airflow Limitation in Adult Bronchial Asthma

Pulmonary Medicine ◽

10.1155/2012/797495 ◽

2012 ◽

Vol 2012 ◽

pp. 1-6 ◽

Cited By ~ 11

Author(s):

Akihiko Ohwada ◽

Kazuhisa Takahashi

Keyword(s):

Bronchial Asthma ◽

Airflow Limitation ◽

Flow Volume ◽

Maximal Expiratory Flow ◽

Volume Curve ◽

Flow Volume Curve ◽

Expiratory Flow

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Determinants of maximal expiratory flow and density dependence in normal humans

Journal of Applied Physiology ◽

10.1152/jappl.1980.49.5.897 ◽

1980 ◽

Vol 49 (5) ◽

pp. 897-904 ◽

Cited By ~ 26

Author(s):

R. G. Castile ◽

R. E. Hyatt ◽

J. R. Rodarte

Keyword(s):

Density Dependence ◽

Vital Capacity ◽

Peripheral Resistance ◽

Lung Mechanics ◽

Large Variability ◽

Maximal Expiratory Flow ◽

Normal Humans ◽

Expiratory Flow ◽

Normal Males ◽

Relationship Of

There is a large variability in maximal expiratory flow (V) and density dependence (DD) in normal humans. Lung mechanics and flow-volume curves were obtained in 40 normal males while they breathed air or helium-oxygen (80%-20%). Static lung recoil (Pst) at 50% vital capacity, total lung capacity, and pulmonary resistance each correlated (P < 0.05) with airflow at 50% vital capacity. The relationship of V and Pst was described by Pst = 1/2 p V2/A2 + RV, where p is gas density, A is the critical area at the flow-limiting site, and R is peripheral resistance. At constant Pst and R, this simplified equation predicts an inverse relation between DD and airflow, which was found at recoil pressures of 8 and 7 cmH2O (P < 0.05). If peripheral losses are small, subjects with smaller flow-limiting airways would have lower airflows but higher DD than subjects with larger airways. Our findings are consistent with concept of dysanaptic growth and suggest that the central airways play a significant role in determining V and DD in normal humans.

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Inhalation patterns and predominant site of bronchoconstriction in healthy subjects

Journal of Applied Physiology ◽

10.1152/jappl.1981.50.3.575 ◽

1981 ◽

Vol 50 (3) ◽

pp. 575-579 ◽

Cited By ~ 4

Author(s):

K. P. Strohl ◽

C. F. O'Cain ◽

R. H. Ingram ◽

M. A. Yanta ◽

W. D. Kaplan ◽

...

Keyword(s):

Density Dependence ◽

Healthy Subjects ◽

Flow Volume ◽

Maximal Flow ◽

Maximal Expiratory Flow ◽

Before And After ◽

Expiratory Flow ◽

The Relationship

To determine the relationship between changes in density dependence of maximal expiratory flow and changes in the predominant site of bronchoconstriction, we altered the pattern of inhalation of a methacholine aerosol to achieve deposition either centrally (by short choppy breaths) or peripherally (by slow deep breaths). Partial expiratory flow volume curves on air and on 80% helium-20% oxygen (HeO2) were recorded in six healthy subjects before and after each pattern of methacholine inhalation. We varied concentrations of methacholine and number of inhalations to achieve equivalent degrees of bronchoconstriction as assessed by decreases in maximal flow (Vmax) on air, which fell 27% from control values. Vmax on HeO2 also fell after both inhalation patterns. Density dependence (Vmax on HeO2 divided by Vmax on air) decreased following slow deep breaths of bronchoconstrictor aerosol, and increased following short choppy breaths. In three subjects, inhalation of radiolabeled methacholine aerosol confirmed that the slow deep pattern was associated with a diffuse, more peripheral deposition, whereas the short choppy pattern led to central deposition. We conclude that changes in density dependence reflect the predominant site of obstruction after acute methacholine aerosol challenge in healthy subjects.

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