Long-term Effects of Postnatal Dexamethasone Treatment on Ventilatory Responses to Exercise in Children Born Prematurely

Abstract

0183 Postnatal dexamethasone treatment has documented short-term benefits on pulmonary function in premature infants as indicated by fewer days on mechanical ventilation and supplemental oxygen; however, the long-term effects are unknown. PURPOSE: To compare ventilatory responses during exercise in children aged 8–10 years born with very low birth weight (VLBW), < 1501g, treated postnatally with a 42-day course of dexamethasone (DEX) with VLBW children given a placebo (CON). The DEX group consisted of 20 children (9 male) and the CON group consisted of 18 children (9 male). METHODS: Each child performed standard spirometry and exercise testing on a cycle ergometer. Resting maximum voluntary ventilation (MVV), aerobic fitness (VO2peak), and ventilatory responses during exercise including minute ventilation (VE), tidal volume (VT), respiratory rate (RR), the ventilatory equivalents for oxygen (VE/VO2), and for carbon dioxide (VE/VCO2) were determined. RESULTS: The groups did not differ significantly by age, height, weight or resting pulmonary function. Mean VO2peak was similar for DEX (40.0 ml · kg-1· min-1) and CON (38.9 ml · kg-1 · min-1), and corresponded to 95 % and 92 % of predicted VO2 based on height and gender. VE, VT, and RR at peak exercise did not differ significantly between the groups; however, the DEX group exhibited a lower VE/MVV at peak exercise (90% v. 108% for DEX and CON), and lower VE/VO2 (31.95 v. 35.43) and VE/VCO2 (30.50 v. 34.18) responses to exercise (p<.05). VO2peak %predicted was correlated with VEpeak (r = .435, p = .023) and VE/MVV (r = .411, p = .033) in the CON group. Neither of these comparisons was significant in the DEX group. CONCLUSION: These results suggest that VLBW children treated with dexamethasone used less of their breathing reserve and had more efficient ventilatory responses to exercise. Furthermore, while pulmonary variables were not significant determinants of fitness among children treated with dexamethasone postnatally, these variables did Influence aerobic fitness among children who did not receive dexamethasone. These results may have implications for better tolerance of everyday activities in VLBW children treated with dexamethasone. Supported in part by a General Clinical Research Center Grant RR M0107122.