Working capacity and pulmonary gas exchange in children with exercise-induced asthma.

Sixteen children aged 10.1-14.3 years with a history of exercise-induced asthma (EIA) were evaluated as to their working capacity both during a maximal exercise test and during submaximal exercise. During submaximal exercise ventilation and alveolar gas exchange were measured. Working capacity was normal with respect to the oxygen uptake and to the maximal load. Arterial blood gases were normal before exercise but PaO2 decreased (p less than 0.01) during the submaximal exercise test. The values were, however, still within the normal limits in all but two of the children. The flow-volume data showed bronchial obstruction in the resting state, before exercise, with lower values of MEF50 and MEF25 (p less than 0.01) than in healthy children. Following exercise, 14 of the 16 children developed clinical symptoms of asthma with increased impairment of the flow-volume curves. Most of them recovered from asthmatic symptoms within 30 min. Flow-volume curves were found to be a sensitive measurement of bronchial obstruction during the symptom-free phase and during EIA although with larger individual variations than FEV1.