Neonatal Correlates Of Ventilatory Responses To Exercise In 8-10 Year Old Children Born With Very Low Birth Weight

Abstract

PURPOSE To examine the relationships between neonatal characteristics, including birth weight (BW), days spent on mechanical ventilation (MV), and postnatal dexamethasone treatment (DEX), with ventilatory responses during exercise in children born prematurely with very low birth weight (VLBW; <1501 g), at 8–10 years of age. Treatment with DEX has documented benefits on pulmonary function in premature infants as indicated by fewer days on MV; however, long-term effects are unknown. From 2002–2003 follow-up of a randomized controlled trial of DEX therapy in VLBW children was completed. Data for 38 VLBW children who completed a maximal exercise test were analyzed for this study. Originally, 20 children (9 male) were treated postnatally with a 42-day course of DEX, and 18 children (9 male) received placebo (CON). METHODS Neonatal data were retrieved from a research database. Each child performed a graded maximal exercise test on a cycle ergometer. Ventilatory responses were measured breath-by-breath via a MedGraphics metabolic cart and included minute ventilation (VE), respiratory rate (bf), and tidal volume (VT) at peak exercise. The nadir of the ventilatory equivalent for carbon dioxide (VE/VCO2nad) was determined to reflect submaximal ventilatory efficiency. RESULTS BW was positively correlated with VE (r = .698, P = .001) and VT (r = .531, P = .023) and negatively correlated with VE/VCO2nad (r = −.509, p = .031) for the CON group only. Spearman correlations revealed a positive trend between time spent on MV and VE/VCO2nad (r = .450, P = .061) in the CON group. Among the DEX group, no significant correlations were observed between ventilatory responses to exercise and BW or MV. CONCLUSIONS For VLBW children not exposed to DEX therapy, higher BW was significantly associated with greater VT and VE at peak exercise, and more time spent on MV was associated with worse ventilatory efficiency during exercise as indicated by a higher VE/VCO2nad. In contrast, no neonatal characteristics were correlated with ventilatory responses to exercise in the DEX group. Our results found no detrimental effects of postnatal DEX exposure, and it appears that DEX disrupts the association between neonatal indices of lung function (MV) and ventilatory efficiency during exercise at school-age. Further research is warranted to determine correlates of ventilatory responses to exercise and subsequent exercise tolerance in VLBW children treated postnatally with DEX. Supported by General Clinical Research Center Grant RR M0107122, the WFU Science Research Fund, and Brenner Children's Hospital Intramural Funding.