VENTILATORY CONTROL DURING EXERCISE IN NORMAL-CHILDREN

We investigated the relation between age and respiratory control durin g exercise in 80 children aged 6.4-17.6 y (42 male, age, 11.6 +/- 3.3 y; body weight, 41.3 +/- 14.7 kg; and 38 female, age, 12.6 +/- 2.7 y; body weight, 42.5 +/- 9.3 kg). Exercise tests were performed on a trea dmill after a standard symptom-limited Bruce protocol. Data were analy zed separately for boys and girls. At rest and at peak exercise, the r atio of minute ventilation to carbon dioxide production ((V) over dot E/(V) over dot CO2), the ratio of effective alveolar ventilation to ca rbon dioxide production ((V) over dot A/(V) over dot CO2, the ratio of pulmonary dead space to tidal volume (V-d/V-t), and arterial Pco(2) ( Paco(2)) were not correlated with age. At the exercise intensity of ve ntilatory anaerobic threshold, the Paco(2) increased, and the (V) over dot A/(V) over dot CO2 decreased, significantly with age, whereas the V-d/V-t, was not related to age. Linear regression analysis demonstra ted that the slope of the relationship between (V) over dot E and (V) over dot CO2 (Delta(V) over dot E/Delta(V) over dot CO2) and the slope of the relationship between (V) over dot A and (V) over dot CO2 (Delt a(V) over dot A/Delta(V) over dot CO2) decreased with age. There were no gender differences in the regression slopes and the intercepts of t he relationships. Results show that younger children breathe more duri ng exercise to eliminate a given amount of CO2 to keep Paco(2) set poi nt slightly but significantly lower than older children. This age depe ndence must be considered in investigating ventilatory control during exercise in children.