Impact of chest radiography‐based definition of bronchopulmonary dysplasia

Background Bubbly/cystic appearance on chest radiograph is an important factor in severe‐type bronchopulmonary dysplasia ( BPD ) in Japan. The aim of this study was to determine the perinatal characteristics and neonatal complications of the bubbly/cystic(+) group in extremely preterm infants with BPD , that is, oxygen dependency at day 28 after birth ( BPD 28). Methods This was a multicenter retrospective cohort study of population data from infants (birthweight, <1,500 g) enrolled in the Neonatal Research Network of Japan. Of the 15 480 infants born at <28 weeks’ gestational age ( GA ) between 2003 and 2012, 8,979 met the BPD 28 criteria. The BPD 28 infants were classified according to bubbly/cystic appearance on radiograph (±) at >28 postnatal days. Results The bubbly/cystic(+) group had lower GA and birthweight and required longer mechanical ventilation and oxygen dependency than the bubbly/cystic(−) group. After adjustment for confounding factors, bubbly/cystic appearance was an independent risk factor for home oxygen therapy at discharge. Conclusion Bubbly/cystic appearance on chest radiograph was a predictor of short‐term respiratory outcomes in infants with BPD 28, which is diagnosed much earlier (≥28 postnatal days), and has a potentially different etiology to BPD 36 (oxygen and/or positive pressure respiratory support dependency at 36 weeks’ postmenstrual age).