Exercise-induced asthma: Is it the right diagnosis in elite athletes?

Exercise-induced asthma, as recognized in asthmatic subjects, is an exagger ated airway response to airway dehydration in the presence of inflammatory cells and their mediators. The airway narrowing is primarily caused by cont raction of bronchial smooth muscle. The milder airway narrowing documented in response to exercise in elite athletes and otherwise healthy subjects ma y simply be the result of the physiologic responses and pathologic changes in airway cells arising from dehydration injury. These changes, which inclu de excessive mucus production and airway edema, would serve both to cause c ough and to amplify the narrowing effects of normal bronchial smooth muscle contraction, resulting in symptoms. These changes are more likely to occur in healthy subjects who exercise intensely for long periods of time breath ing cold air, dry air, or both. Under these conditions, the ability to humi dify inspired air may be overwhelmed, causing significant dehydration of th e airway mucosa and an increase in osmolarity, even in small airways. In ad dition to dehydration injury, airway narrowing to pharmacologic and physica l agents may occur as a result of injury caused by large volumes of air con taining irritant gases, particulate matter, or allergens being inspired dur ing exercise. As a result, the airways may become inflamed, and the airway smooth muscle may become more sensitive. These events could result in the s ame exaggerated airway response to dehydration, as documented in asthmatic subjects.