Exercise-induced biphasic responses and methacholine reactivity in asthma

Area of Science:

• Pediatric Pulmonology
• Allergy and Immunology
• Exercise Physiology

Background:

• Exercise-induced asthma (EIA) can manifest as early or biphasic responses.
• Biphasic allergen-induced asthma is known to increase bronchial hyperreactivity.
• The impact of biphasic exercise responses on bronchial hyperreactivity in children was previously uninvestigated.

Purpose of the Study:

• To investigate whether biphasic asthmatic responses to exercise in children are associated with increased bronchial hyperreactivity.
• To compare the effects of exercise challenge with allergen challenge on bronchial responsiveness.

Main Methods:

• Forty-three children with reproducible EIA underwent exercise challenge.
• Methacholine provocative dose 20 (PD20) forced expiratory volume in 1 second (FEV1) was measured before and after exercise.
• Children were categorized based on early, or early and late, asthmatic responses to exercise.

Main Results:

• Seven out of 43 children exhibited biphasic (early and late) asthmatic responses to exercise.
• No significant changes in methacholine PD20 FEV1 were observed post-exercise in children with early or biphasic responses.
• This contrasts with allergen-induced asthma, where late reactions often enhance bronchial responsiveness.

Conclusions:

• Exercise challenge in asthmatic children does not appear to induce the prolonged increase in bronchial hyperreactivity seen with allergen exposure.
• These findings suggest distinct pathophysiological mechanisms between exercise-induced and allergen-induced asthma.
• The results are reassuring for recommending physical activity and training programs for children with EIA.