Density dependence of maximal expiratory flow before and during tracheal constriction in dogs

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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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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Density dependence of maximal flow in dogs with central and peripheral obstruction

Journal of Applied Physiology ◽

10.1152/jappl.1983.55.3.717 ◽

1983 ◽

Vol 55 (3) ◽

pp. 717-725 ◽

Cited By ~ 8

Author(s):

R. G. Castile ◽

O. F. Pedersen ◽

J. M. Drazen ◽

R. H. Ingram

Keyword(s):

Density Dependence ◽

Vital Capacity ◽

Forced Expiration ◽

Flow Volume ◽

Partial Obstruction ◽

Volume Curve ◽

Before And After ◽

Lower Lung ◽

Maximum Expiratory Flow ◽

Flow Volume Curve

In 12 anesthetized, tracheotomized, vagotomized, open-chested, mongrel dogs we measured end and side hole airway pressures during forced expiration using a Pitot static probe. Volume was obtained as the integral of flow from a dog plethysmograph with frequency response adequate to 20 Hz. Equal pressure points (EPPs) and choke points (CPs) were located with dogs breathing air or a mixture of 80% helium-20% oxygen (HeO2) before and after partial obstruction of the trachea and intravenous histamine and propranolol. At 50% of vital capacity (VC) the CP was in the trachea in 11 of 12 dogs. Partial obstruction of the trachea decreased flow during the plateau of the maximum expiratory flow-volume curve (MEFVC) with the CP remaining in the trachea. The MEFVC plateau was extended to a lower lung volume. At 50% of VC the EPP moved downstream and density dependence remained high. Histamine and propranolol caused EPPs and CPs to move towards the periphery and density dependence to decrease. The shape of the MEFVC changed as the plateau was shortened and, in some instances, abolished. A plateau on the MEFVC could be regenerated by partial obstruction of the trachea. This was accompanied by return of the CP to the trachea and an increase in density dependence. Changes in density dependence were found to be a result of both the relocation of sites of flow limitation and differences in local CP areas with HeO2 and air.

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Changes in flow-volume curve configuration with bronchoconstriction and bronchodilation

Journal of Applied Physiology ◽

10.1152/jappl.1986.61.6.2243 ◽

1986 ◽

Vol 61 (6) ◽

pp. 2243-2251 ◽

Cited By ~ 9

Author(s):

C. R. O'Donnell ◽

R. G. Castile ◽

J. Mead

Keyword(s):

Vital Capacity ◽

Normal Subjects ◽

Flow Volume ◽

Slope Ratio ◽

Lung Volumes ◽

Volume Curve ◽

Before And After ◽

Lower Lung ◽

Maximum Expiratory Flow ◽

Flow Volume Curve

Changes in the configuration of maximum expiratory flow-volume (MEFV) curves following mild degrees of bronchodilation or bronchoconstriction were studied in five normal and five asthmatic subjects. In a volume-displacement plethysmograph, MEFV curves were performed before and after inhalation of aerosolized isoproterenol (I) or histamine (H). Five filtered MEFV curves were averaged, and slope ratio vs. volume (SR-V) plots were obtained from averaged curves. Following I, maximal flows at 75% of the vital capacity (VC) were decreased in asthmatics but not in normal subjects. Flows at 50 and 25% of the VC increased in normal subjects and asthmatics, whereas VC′s were unchanged. In asthmatics, sudden large decreases in flow (bumps) occurred at lower lung volumes following I. H reduced flows over the entire VC, with greater reductions occurring in asthmatics than in normals, particularly at low lung volumes. In asthmatics, VC was slightly reduced, and bumps in MEFV curve configuration occurred at higher lung volumes or were abolished entirely following H. A reduction in the amount of configurational detail appreciable in MEFV curves following histamine in asthmatics was best seen in SR-V plots. Following H, SR′s decreased regularly with decreasing lung volume in all the asthmatics but in none of the normals. This was the single most striking finding of this study. Mild I- and H-induced perturbations of airway bronchomotor tone produced small but consistent changes in MEFV curve configuration.(ABSTRACT TRUNCATED AT 250 WORDS)

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Shape Analysis of the Maximal Expiratory Flow Volume Curve Among the Patients with Various Kind of Pulmonary Diseases

Tuberculosis and Respiratory Diseases ◽

10.4046/trd.1982.29.1.30 ◽

1982 ◽

Vol 29 (1) ◽

pp. 30-36

Author(s):

Song Hyun Nam ◽

Hyun Ha Park ◽

Re Hwe Kim ◽

Sung Koo Han ◽

Ye Won Kim ◽

...

Keyword(s):

Shape Analysis ◽

Pulmonary Diseases ◽

Flow Volume ◽

Maximal Expiratory Flow ◽

Volume Curve ◽

Flow Volume Curve ◽

Expiratory Flow

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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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Spirometry and Maximal Expiratory Flow-Volume Curve Reference Standards for Polynesian, European, and Chinese Teenagers

CHEST Journal ◽

10.1378/chest.94.4.792 ◽

1988 ◽

Vol 94 (4) ◽

pp. 792-798 ◽

Cited By ~ 14

Author(s):

Françoise Neukirch ◽

René Chansin ◽

Renata Liard ◽

Monique Levallois ◽

Philippe Leproux

Keyword(s):

Reference Standards ◽

Flow Volume ◽

Maximal Expiratory Flow ◽

Volume Curve ◽

Flow Volume Curve ◽

Expiratory Flow

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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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