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The refractory period after eucapnic voluntary hyperventilation challenge and its effect on challenge technique
G J Argyros1, J M Roach, K M Hurwitz
1Department of Medicine, Walter Reed Army Medical Center, Washington, DC 20307-5001, USA.
Chest
|August 1, 1995
Summary
Asthma patients exhibit a refractory period after eucapnic voluntary hyperventilation (EVH) challenges. Repeated EVH significantly reduces bronchoconstriction, impacting responses to interrupted challenges.
Area of Science:
- Respiratory Medicine
- Pulmonary Physiology
Background:
- Asthma is a chronic respiratory disease characterized by airway inflammation and hyperresponsiveness.
- Eucapnic voluntary hyperventilation (EVH) is a common challenge test to assess airway hyperresponsiveness in asthma.
Purpose of the Study:
- To investigate the existence of a refractory period (RP) following EVH challenges in individuals with asthma.
- To compare the bronchoconstrictive response to continuous versus interrupted EVH challenges.
Main Methods:
- Eleven individuals with known asthma underwent serial EVH challenges using dry, room-temperature air.
- Minute ventilation was standardized to 30 times the pre-challenge FEV1 for 6-minute durations.
- Bronchoconstriction was assessed by the post-challenge fall in FEV1.
Main Results:
- A significant reduction in the fall of FEV1 was observed between the initial EVH challenge (27.4%) and a second, repeated EVH challenge (16.1%, p=0.0001), indicating refractoriness.
- An interrupted EVH challenge (2 min repeated thrice) resulted in a significantly smaller FEV1 fall (18.9%) compared to a continuous 6-minute EVH challenge (27.4%, p=0.036).
Conclusions:
- This study demonstrates a significant refractory period after repeated EVH challenges in asthmatic individuals.
- The observed refractoriness influences the bronchospastic response to both repeated and interrupted EVH challenges.