The importance of ventilation in exercise-induced asthma

The degree of post treadmill-running decrease in pulmonary function (Exercise-Induced Asthma) in 11 adult asthmatics was compared with the decrease in pulmonary function followed by resting isocapnic hyperventilation. It was checked that ventilation during the hyperventilation was kept identical to the ventilation during treadmill-running by continuous recording of respiratory frequency, minute ventilation, tidal volume and accumulated ventilation. The temperature of the inspired air was identical in the two situations and the relative humidity was 40% during treadmill-running and 15% during hyperventilation. The average accumulated ventilation during treadmill-running and hyperventilation was 411 1/6 min in both events. The decrease in peak expiratory flow after treadmill-running was 25% and after isocapnic hyperventilation 24%. It is concluded that the ventilation is of more importance for the decrease in pulmonary function after exercise, than the work load.