Exercise-induced bronchoconstriction as an expression of bronchial hyperreactivity: a study of its mechanisms in children.

Abstract

The mechanism of exercise-induced bronchoconstriction (EIB) was studied by observing the protective effects of several aerosol agents in a double-blind, randomized trial. Exercise-induced bronchoconstriction was not affected by placebo but was reduced by each agent used (P < 0.001). Blocking the parasympathetic system had the weakest effect, while .beta.2 adrenergic stimulation produced the strongest effect which was significantly different from the parasympatholytic (P < 0.02). The effect of the mast cell stabilizer, sodium cromoglycate (SCG), was intermediate. In some patients SCG had a stronger effect than the .beta.2 adrenergic agonist. A relationship was found between EIB and bronchial hyperreactivity induced by histamine (P < 0.05).