Effects of birthweight and oxygen supplementation on lung function in latechildhood in children of very low birth weight

Impaired respiratory function has been found frequently in ex-premature chi ldren, but it is unclear which specific factors influence this impairment t he most. The aim of this study was to determine the importance of the contr ibutions of birth weight, gestational age, neonatal respiratory disease, an d its treatment on subsequent childhood lung function at age 11 years In a cohort of children of very low birth weight (VLBW; less than or equal to 1, 500 g). Detailed clinical histories were recorded, and lung function was me asured in 60% (102 children) of surviving VLBW infants born 1981/1982, and compared with 82 matched control children (birth weight >2,000 g) of simila r age. VLBW children were shorter and lighter than controls (P < 0.0001) at 11 yea rs of age, and had reduced expiratory flows (P < 0.00001) and forced vital capacities (P < 0.001). The residual volume to total lung capacity ratio (R V/TLC ratio) was increased (P < 0.00001), while total lung capacity (TLC) r emained unchanged. Those with bronchopulmonary dysplasia (BPD) had the lowe st mean expiratory flows. Males had lower expiratory flows than females. On univariate analysis, gestational age by itself accounted for 8.8% of the e xplained variance in FEV, at 11 years of age, but birth weight accounted fo r 16% on its own; both together accounted for a further 0.2% (16.2%), sugge sting that the latter was the dominant factor. On multivariate analysis, th e contribution of birth weight and gestational age was small, and the best predictors at 11 years of age, which together explained 43.4% of the total variance in FEV1, were log days of supplemental oxygen (9.6%) and a reporte d history of asthma (10.8%). For FEF25-75 these predictors explained 7.2% a nd 13.4%, respectively, of the total explained variance of 40.6%. The relat ion between neonatal oxygen supplementation and childhood FEV1 was such tha t up to 20 days of supplemental oxygen had little effect on subsequent FEV1 at 11 years of age, but each additional week of supplemental oxygen after that time was associated with a progressive reduction in FEV1 of 3%. These data confirm the significant role of supplemental oxygen in the neona tal period and a history of asthma on the subsequent reduction of expirator y flows in VLBW children. Birth weight was a more important prenatal factor than gestational age, but both were of lesser predictive significance than either supplemental oxygen or a reported history of asthma. (C) 2000 Wiley -Liss, Inc.