Early prediction of chronic oxygen dependency by lung function test results

Chronic oxygen dependency (COD) is a common sequela to very premature birth. Steroid therapy may reduce COD if given within the first 2 weeks, but has important side effects. It is, therefore, crucial to identify an accurate predictor of COD and hence only expose high-risk infants to intervention therapy. The aim of this study was to determine if, within 48 hr of birth, abnormal lung function predicted COD and whether such results performed better than readily available clinical data. Results from 100 consecutive, very low birth-weight infants, median gestation age 28 weeks (range, 24-33), who were ventilated within 6 hr of birth and survived beyond 36 weeks postconceptional age (PCA), were analyzed. Lung volume was assessed by measurement of functional residual capacity (FRC) using a helium gas dilution technique, and compliance was measured using either a passive inflation or an occlusion technique. The maximum peak inflating pressure and inspired oxygen concentration within the first 48 hr were recorded. The infants who remained oxygen-dependent beyond 28 days (n = 58) and 36 weeks PCA (n = 24) differed from the rest in being more immature (P < 0.001), more had a patent ductus arteriosus, and they had both a lower median lung volume (P < 0.001) and lower compliance (P < 0.01) on day 2. An FRC <19 mL/kg and a low gestational age were the most accurate predictors of COD at 28 days. An FRC <19 mL/kg on day 2 remained the best predictor of COD beyond 28 days if only the 50 infants whose gestational age was < or = 28 weeks were considered. We conclude that demonstration of a low lung volume in the first 48 hr helps to identify infants who might benefit from therapy aimed at preventing COD.