Comparison of airway reactivity induced by cold air and metacholine challenges in asthmatic children.

Bronchial responsiveness to isocapnic hyperventilation with cold air (CAH) and to inhaled methacholine (MCH) was compared in 17 children with bronchial asthma. The response to cold air was expressed as the percent drop in FEV1 from baseline at 4 min. after the challenge (delta % FEV1 CAH), and the response to methacholine as the provocative concentration required to reduce the FEV1 by 20% from baseline (PC20MCH). Both tests were sensitive (94%) for detecting airway hyperreactivity. There was no statistically significant relationship between delta % FEV1 CAH and the log PC20MCH (r = 0.39; P = 0.12). In clinical practice, methacholine test is easier to perform, but in the research field cold air challenge may be preferable because it avoids potential drug effects.