RESPIRATORY GAS EXCHANGE AT REST AND DURING EXERCISE IN NORMAL AND ASTHMATIC CHILDREN

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Abstract
Forced expiratory volume [FEV], static lung volume, physiologic dead space for CO2, acid-base status, and the respiratory exchange ratio were studied in 12 asthmatic children in remission and 18 normal children at rest and during exercise on a bicycle ergometer. The mean FEV was significantly lower in the asthmatic children compared to the normal group. This mean measurement remained unchanged after exercise, although there were considerable individual variations. The physiologic dead space, as evaluated from the CO2 exchange data, was significantly greater in the asthmatic group, but did not increase or decrease as a result of exercise in either group. A significant metabolic acidosis developed in 4 of the 12 asthmatic children during exercise. This was paralleled by a rise in respiratory exchange ratio. The mechanism of development of this acidosis in the presence of a normal arterial PCO2 [CO2 pressure] is not obvious; but in view of the known sensitivity of pulmonary circulation to an increase in hydrogen ion concentration, this mechanism deserves further study.