The correlation between exercise-induced bronchoconstriction and bronchial methacholine sensitivity in asthma.

A possible relationship between exercise-induced bronchoconstriction (EIB) and bronchial sensitivity to the cholinergic drug, metacholine, was studied. On the same day, 57 asthmatic subjects inhaled increasing concentrations of the drug and were then tested for EIB by exercising to exhaustion. A fall in peak expiratory flow rate of 15% or more was considered a positive reaction to either test. Of the 45 patients exhibiting a positive methacholine reaction, 33 showed bronchoconstriction after exercise (including three of the ten who had no previous history of exertional asthma) while none of the 12 methacholine nonreactors developed EIB. This significant correlation (P is less than .001) between the tendency to develop EIB and sensitivity to methacholine suggests that bronchoconstriction, induced either by exercise or methacholine, is a specific reaction.