Pathophysiology of exercise-induced asthma.

The initiating stimulus for exercise-induced asthma in airway mucosal cooling or drying is caused by heat and water losses during exercise-related hyperventilation. It is not known how this stimulus is translated to bronchoconstriction, but the most convincing evidence is that mast cells are activated and release bronchospastic chemical mediators. The obstructive response appears to depend on the existence of abnormally reactive airways characteristically found in asthmatics. A number of modifying factors may be found during exercise, including plasma changes in catecholamines and metabolite and acid-base status.