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Changes in flow-volume curve configuration with bronchoconstriction and bronchodilation.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|December 1, 1986
Summary
Mild airway changes from bronchodilators and bronchoconstrictors cause subtle shifts in maximum expiratory flow-volume (MEFV) curves. These alterations, particularly in asthmatics, are detectable using slope ratio plots.
Area of Science:
- Pulmonary Physiology
- Respiratory Medicine
Background:
- Maximum expiratory flow-volume (MEFV) curves assess airflow dynamics.
- Airway reactivity influences MEFV curve configuration.
Purpose of the Study:
- To investigate changes in MEFV curve configuration after mild bronchodilation and bronchoconstriction.
- To compare responses in normal and asthmatic subjects.
Main Methods:
- Subjects performed MEFV maneuvers before and after inhaling isoproterenol or histamine.
- Volume-displacement plethysmography was used.
- Slope ratio vs. volume (SR-V) plots were derived from averaged MEFV curves.
Main Results:
- Isoproterenol decreased flow at 75% vital capacity (VC) in asthmatics; histamine reduced flow across the entire VC, especially in asthmatics.
- Asthmatics showed "bumps" in MEFV curves after isoproterenol and altered configurations after histamine.
- SR-V plots revealed reduced configurational detail in asthmatics post-histamine, with SRs decreasing with lung volume.
Conclusions:
- Mild perturbations in airway tone induce consistent, albeit small, changes in MEFV curve configuration.
- SR-V plots are sensitive to subtle MEFV curve alterations in asthmatics.
- Airway reactivity significantly impacts MEFV curve morphology.