Heterogeneity in the response of asthmatic patients to pre-exercise treatment with cromolyn sodium

The protective effect of pre-exercise treatment with cromolyn sodium (CS) on exercise-induced asthma (EIA) was investigated. Ten children and young adults each exercised for 6 min by cycling on a cycle ergometer while breathing cold dry air. Each subject performed 2 tests in which ventilation, heart rate, and gas exchange were closely matched; 15 min prior to each test, the patient inhaled either placebo or CS powder in a double-blind, randomized fashion. All subjects were found to be protected by CS, as manifested by a postexercise fall in FEV₁ of 14 ± 4% SE compared with the control postexercise fall of 39 ± 5%. All 10 subjects had participated in a previous study, and we found that the 3 subjects who were not rendered refractory to EIA by a prior warm humid exercise test were only minimally protected by CS, whereas the 7 other patients who were rendered refractory to EIA, even by warm humid exercise, were greatly protected by CS. This finding suggests that there exists a consistent heterogeneity in the response of asthmatic patients to exercise, possibly related to the individual site of receptors or of airway hyperreactivity.