DEVELOPMENTAL PATTERN OF HYPERCAPNIC AND HYPOXIC VENTILATORY RESPONSES FROM CHILDHOOD TO ADULTHOOD

The developmental pattern of ventilatory responses, through childhood and puberty into adulthood, is not known. Therefore we studied hyperca pnic (HCVR) and hypoxic ventilatory responses (HOVR) in 59 subjects (2 9 males and 30 females) 4-49 yr of age, of whom 35 were children (<18 yr old). There was a significant correlation between HCVR and weight ( r = 0.33, P < 0.02), vital capacity (r = 0.30, P < 0.05), and body sur face area (r = 0.30, P < 0.05) but not height (r = 0.22, NS). There wa s no correlation between HOVR and any of the correcting factors. To ac count for disparities in body size, volume-related results were scaled for body weight. The HCVR corrected for weight (HCVR/WT) decreased wi th age (r = -0.57, P < 0.001). HCVR/WT was significantly higher in chi l dren than in adults (0.056 +/- 0.024 vs. 0.032 +/- 0.015 l.kg(-1).mi n(-1).Torr end-tidal PCO2-1, P < 0.001). The (tidal volume/inspiratory duration)/weight, respiratory rate, and heart rate responses to hyper capnia were increased in the children, and the CO, threshold was lower (36 +/- 5 vs. 40 +/- 6 Torr, P < 0.05). Similarly, the HOVR corrected for weight (HOVR/WT) decreased with age (r = 0.34, P ( 0.05), and HOV R/WT was significantly higher in children than in adults (-0.035 +/- 0 .017 vs. -0.024 +/- 0.016 l.kg-1.min-1.%arterial O-2 saturation(-1) P < 0.02). The respiratory rate and heart rate responses to hypoxia were increased in the children. We conclude that rebreathing HCVR and HOVR are higher during childhood than during adulthood.