Partial and Maximal Expiratory Flow-Volume Curves in Normal and Asthmatic Subjects Before and After Inhalation of Metaproterenol

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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Pattern and mechanism of airway response to hypocapnia in normal subjects

Journal of Applied Physiology ◽

10.1152/jappl.1979.47.1.8 ◽

1979 ◽

Vol 47 (1) ◽

pp. 8-12 ◽

Cited By ~ 35

Author(s):

C. F. O'Cain ◽

M. J. Hensley ◽

E. R. McFadden ◽

R. H. Ingram

Keyword(s):

Vital Capacity ◽

Normal Subjects ◽

Oxygen Mixture ◽

Flow Volume ◽

Mixture Density ◽

Lung Capacity ◽

Airway Constriction ◽

Maximal Expiratory Flow ◽

Airway Response ◽

Expiratory Flow

We examined the bronchoconstriction produced by airway hypocapnia in normal subjects. Maximal expiratory flow at 25% vital capacity on partial expiratory flow-volume (PEFV) curves fell during hypocapnia both on air and on an 80% helium- 20% oxygen mixture. Density dependence also fell, suggesting predominantly small airway constriction. The changes seen on PEFV curves were not found on maximal expiratory flow-volume curves, indicating the inhalation to total lung capacity substantially reversed the constriction. Pretreatment with a beta-sympathomimetic agent blocked the response, whereas atropine pretreatment did not, suggesting that hypocapnia affects airway smooth muscle directly, not via cholinergic efferents.

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

Journal of Applied Physiology ◽

10.1152/jappl.1986.60.3.1060 ◽

1986 ◽

Vol 60 (3) ◽

pp. 1060-1066 ◽

Cited By ~ 4

Author(s):

R. G. Castile ◽

O. F. Pedersen ◽

J. M. Drazen ◽

R. H. Ingram

Keyword(s):

Density Dependence ◽

Lung Volumes ◽

Maximal Expiratory Flow ◽

Volume Curve ◽

Before And After ◽

Lower Lung ◽

Flow Volume Curve ◽

Expiratory Flow ◽

Longitudinal Extension ◽

Central Airway

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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Volume Adjustment of Maximal Expiratory Flow Rates of Flow-Volume Loops

CHEST Journal ◽

10.1378/chest.102.5.1636-c ◽

1992 ◽

Vol 102 (5) ◽

pp. 1636-1637

Author(s):

Sema Umut ◽

Bilun Gemicioğlu ◽

Nurhayat Yildirim

Keyword(s):

Flow Volume ◽

Flow Rates ◽

Maximal Expiratory Flow ◽

Expiratory Flow ◽

Expiratory Flow Rates

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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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Effects of atropine on potentiation of exercise-induced bronchospasm by cold air

Journal of Applied Physiology ◽

10.1152/jappl.1978.45.2.238 ◽

1978 ◽

Vol 45 (2) ◽

pp. 238-243 ◽

Cited By ~ 34

Author(s):

E. C. Deal ◽

E. R. McFadden ◽

R. H. Ingram ◽

J. J. Jaeger

Keyword(s):

Ambient Air ◽

Small Airways ◽

Flow Limitation ◽

Ambient Conditions ◽

Cold Air ◽

Relative Contribution ◽

Maximal Expiratory Flow ◽

Before And After ◽

Expiratory Flow ◽

Exercise Induced

The role of vagal efferent activity in the cold air potentiation of exercise-induced asthma was assessed by exercising nine subjects who breathed air at ambient and subfreezing temperatures before and after cholinergic blockade. Lung volumes and maximal expiratory flow volume curves with air and with 80% helium-20% oxygen were obtained before and 5--10 min after each challenge. Isovolume comparisons of maximal expiratory flow rates with the two gases were used to assess relative contributions of large and small airways to flow limitation. Exercise under ambient conditions resulted in the expected airway obstruction and cold air exaggerated the response. Atropine pretreatment had no effect on the cold air potentiation. After atropine with ambient air exercise, there was an increase in the relative contribution of large airways to flow limitation, whereas exercise with cold air resulted in an increase in the contribution of small airways. We concluded that the potentiating effects of cold air are local and suggest that the immediate stimulus is related to cooling of intrathoracic airways.

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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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