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Expiratory glottic widening in asthmatic subjects during exercise-induced bronchoconstriction
I Rubinstein1, N Zamel, A S Slutsky
1Department of Medicine, St. Michael's Hospital, Toronto, Ontario, Canada.
The American Review of Respiratory Disease
|September 1, 1989
Summary
Exercise-induced asthma causes glottic widening, unlike other airway narrowing. This widening occurs with decreased lower airway caliber, suggesting varied glottic aperture responses in asthma.
Area of Science:
- Respiratory physiology
- Pulmonary medicine
- Asthma research
Background:
- Glottic caliber influences airway resistance and breathing effort.
- Histamine or methacholine cause midexpiratory glottic narrowing.
- Exercise typically leads to midexpiratory glottic widening in healthy individuals.
Purpose of the Study:
- To investigate glottic aperture changes during exercise-induced bronchoconstriction in asthmatic subjects.
- To determine if glottic narrowing occurs during exercise-induced asthma.
- To compare glottic responses in exercise-induced asthma versus other asthma triggers.
Main Methods:
- Acoustic reflection technique was used to measure midexpiratory glottic cross-sectional area.
- Seven asthmatic subjects underwent exercise challenges.
- Forced expiratory volume in 1 second (FEV1) was measured to assess bronchoconstriction.
Main Results:
- Exercise induced a significant fall in FEV1 (38%) in asthmatic subjects.
- Midexpiratory glottic cross-sectional area significantly increased during exercise-induced bronchoconstriction (from 1.89 to 2.36 cm2).
- Glottic widening was associated with increased tidal flow rates.
Conclusions:
- Exercise-induced asthma is characterized by midexpiratory glottic widening, contrasting with histamine/methacholine-induced narrowing.
- This glottic widening occurs alongside lower airway caliber reduction.
- Glottic aperture modulation in acute asthma is stimulus-dependent and heterogeneous.