Biphasic (early and late) asthematic responses to exercise in children with severe asthma, resident at high altitude

Abstract

Twenty-three children with severe asthma who had been resident at high altitude for at least 3 months, considerably reduced their requirement for regular anti-asthma therapy. On a standard exercise challenge in low humidity, ten had no response, seven had isolated immediate bronchospasm and six had biphasic responses with immediate bronchospasm followed 4–10 h later by a late reaction sustained for at least 2h. The existence of biphasic responses after exercise, similar to those observed after antigen challenge, supports the concept of mast cell involvement in exercise-induced asthma.