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Analysis of refractory period after exercise and eucapnic voluntary hyperventilation challenge
R R Rosenthal1, B L Laube, D B Hood
1Department of Medicine, Johns Hopkins University Medical Institutions, Baltimore, MD 21224.
The American Review of Respiratory Disease
|February 1, 1990
Summary
This study found that repeated exercise or eucapnic voluntary hyperventilation (EVH) challenges induce similar refractoriness in patients with exercise-induced asthma, suggesting comparable protective effects after airway challenges.
Area of Science:
- Pulmonary Medicine
- Respiratory Physiology
Background:
- Exercise-induced asthma is a common condition.
- Understanding airway refractoriness is crucial for managing asthma.
Purpose of the Study:
- To compare the degree of refractoriness after repetitive exercise versus eucapnic voluntary hyperventilation (EVH) challenges in patients with exercise-induced asthma.
- To determine if matched inspired air conditions and ventilation influence refractoriness.
Main Methods:
- Ten patients with exercise-induced asthma underwent two study days.
- On each day, subjects performed either an exercise or an EVH challenge with matched ventilation and inspired air conditions.
- A second identical challenge was administered once lung function (FEV1) recovered to 90% of baseline or after 3.75 hours.
Main Results:
- Both first and second exercise challenges resulted in significantly reduced FEV1 (52% and 58% of predicted, respectively).
- Both first and second EVH challenges also significantly reduced FEV1 (52% and 59% of predicted, respectively).
- A higher percentage of subjects showed improved specific airway conductance (SGaw) after the second challenge for both exercise (70%) and EVH (80%).
Conclusions:
- Repetitive exercise and EVH challenges, when matched for ventilation and inspired air conditions, induce similar degrees of airway refractoriness in patients with exercise-induced asthma.
- The protective effect, measured by FEV1, was comparable between the two challenge types.
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