Bronchopulmonary dysplasia and expiratory airflow at 8 years in children born extremely preterm in the post-surfactant era
Lex W. Doyle, Sarath Ranganathan, Jeanie L.Y. Cheong
Abstract
Background It is unclear if bronchopulmonary dysplasia (BPD) is independently associated with reduced expiratory airflow at school age. Objective To 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). Methods All 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 (FEV 1 ), were measured and values converted to z-scores. Results Compared with no BPD (n=94), moderate–severe BPD (n=193) was associated with a substantial reduction in expiratory airflow (eg, zFEV 1 mean difference −0.69, 95% CI −0.97 to –0.41; p<0.001), but mild BPD (n=131) was not (zFEV 1 mean 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 (zFEV 1 mean difference −0.63, 95% CI −0.92 to –0.33; p<0.001), but mild BPD (zFEV 1 mean difference 0.04, 95% CI −0.26 to 0.34; p=0.27), gestational age (zFEV 1 0.06 mean increase per week, 95% CI −0.05 to 0.17; p=0.29) and birth weight z-score (zFEV 1 0.07 mean increase per SD, 95% CI −0.06 to 0.20; p=0.28) were not. Conclusions In children born EP, moderate–severe BPD, but not mild BPD was independently associated with reduced expiratory airflow at 8 years.