Ventilatory Control during Exercise in Normal Children

We investigated the relation between age and respiratory control during 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 treadmill after a standard symptom-limited Bruce protocol. Data were analyzed separately for boys and girls. At rest and at peak exercise, the ratio of minute ventilation to carbon dioxide production (VE/Vco 2 ), the ratio of effective alveolar ventilation to carbon dioxide production (VA/Vco 2 ), 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 ventilatory anaerobic threshold, the Paco 2 increased, and the VA/Vco 2 decreased, significantly with age, whereas the V d /V t was not related to age. Linear regression analysis demonstrated that the slope of the relationship between V E and Vco 2 (ΔVE/ΔVCO 2 ) and the slope of the relationship between VA and Vco 2 (ΔVA/ΔVco 2 ) decreased with age. There were no gender differences in the regression slopes and the intercepts of the relationships. Results show that younger children breathe more during exercise to eliminate a given amount of CO 2 to keep Paco 2 set point slightly but significantly lower than older children. This age dependence must be considered in investigating ventilatory control during exercise in children.