Exercise-induced asthma.

Bronchoconstriction associated with exercise can occur in nearly all individuals with asthma and in 35-40% of those with allergic rhinitis/hay fever symptoms. This represents approximately 12-15% of the population. Exercise-induced asthma (EIA) is a clinical syndrome characterized by transient airflow obstruction typically 5-15 min after cessation of physical exertion. Symptoms may include chest tightness, breathlessness, coughing, and/or wheezing. Some individuals may experience delayed bronchoconstriction (late phase response) 6-10 h after completing exercise. Approximately 40-50% of those with asthma exhibit a "refractory period", i.e., diminished bronchoconstriction to exercise performed within 2 h. The pathophysiology of EIA is related to thermal events within the intrathoracic airways. Alterations in the temperature of the airways and/or osmolarity in the epithelial lining fluid cause release of mediators in the airways and the development of bronchoconstriction. Although EIA can be strongly suspected by an appropriate history, pulmonary function testing is necessary to make a specific diagnosis. Measurement of lung function is an important first diagnostic test. If there is no evidence of airflow obstruction at rest, then either bronchoprovocation testing or exercise challenge testing is indicated. Nonpharmacologic therapy includes "warm-up" exercise prior to training or competition to induce a "refractory period" and to prevent/reduce bronchoconstriction. An inhaled beta 2-adrenergic agonist, e.g., albuterol, is usually effective for preventing/treating EIA. Cromolyn sodium is an alternative class of medication that inhibits both the early and late phase responses. Other bronchodilator agents are available if combination therapy with an inhaled beta 2-adrenergic agonist and cromolyn sodium is not effective.(ABSTRACT TRUNCATED AT 250 WORDS)