Bronchopulmonary dysplasia and expiratory airflow at 8 years in children born extremely preterm in the post-surfactant era

Abstract

BackgroundIt is unclear if bronchopulmonary dysplasia (BPD) is independently associated with reduced expiratory airflow at school age.ObjectiveTo determine the independent associations of moderate–severe BPD, mild BPD, gestational age and birth weight z-score with expiratory airflow in children born extremely preterm (EP; <28 weeks’ gestation).MethodsAll EP survivors born in Victoria, Australia, in three eras (1991–1992, n=225; 1997, n=151; and 2005, n=170) were recruited at birth and 418/546 (77%) had valid spirometry data at 8 years. BPD was classified as moderate–severe (oxygen requirement at 36 weeks’ postmenstrual age), or mild (oxygen >28 days but not at 36 weeks’ postmenstrual age). Expiratory airflow variables, including the forced expired volume in 1 s (FEV1), were measured and values converted to z-scores.ResultsCompared with no BPD (n=94), moderate–severe BPD (n=193) was associated with a substantial reduction in expiratory airflow (eg, zFEV1mean difference −0.69, 95% CI −0.97 to –0.41; p<0.001), but mild BPD (n=131) was not (zFEV1mean difference 0.01, 95% CI −0.28 to 0.31; p=0.93). On multivariable analysis, moderate–severe BPD remained strongly associated with reduced airflow (zFEV1mean difference −0.63, 95% CI −0.92 to –0.33; p<0.001), but mild BPD (zFEV1mean difference 0.04, 95% CI −0.26 to 0.34; p=0.27), gestational age (zFEV10.06 mean increase per week, 95% CI −0.05 to 0.17; p=0.29) and birth weight z-score (zFEV10.07 mean increase per SD, 95% CI −0.06 to 0.20; p=0.28) were not.ConclusionsIn children born EP, moderate–severe BPD, but not mild BPD was independently associated with reduced expiratory airflow at 8 years.