Respiratory gas exchange at rest and during exercise in normal and asthmatic children.

Since 1951 (1) it has been known that patients with spasmodic asthma in apparent clinical remission may have significant ventilatory impairment and abnormal inert gas distribution. Two recent studies have indicated that this state is probably accompanied by considerable abnormality of ventilation/perfusion distribution. Bentivoglio and associates (2) measured the rate of equilibration of xenon133 in different lung zones and found impairment of gas distribution on a regional basis in 6 of 12 asthmatic adults without disturbance of perfusion to the same zones. Ledbetter and co-workers (3), measuring alveolararterial nitrogen tension differences, found elevated values indicating the persistence of perfusion to poorly ventilated zones in the lungs of symptom-free asthmatic children who had diminished ventilatory function. From all indications, only two studies so far have been reported, which concern possible adaptations of asthmatic children to the stress of exercise. Engstrom and associates ( 4), found that exercise caused an increase in compliance and in airway resistance. Jones and co-workers (5) related changes in forced expiratory volume (FEV) in asthmatic children to the function of exercise finding an increase after a oneto two-minute period of running and a significant decrease after an eightto twelveminute period. These results could not be reproduced when the exercise was performed on a bicycle ergometer. The present series of experiments was designed to compare a group of normal children with a group of asthmatic children of com-