Table 1.

Definitions

 Normal or near normal (NL)
  (1)  No respiratory distress or transient oxygen requirement, for less than 4 hours and
  (2)  Normal x-ray or x-ray consistent with transient tachypnea of the newborn
  (3)  Occasional need for oxygen (<3 days) for procedures was allowed
 Respiratory distress syndrome (RDS)
  (1)  Acute respiratory distress requiring oxygen for at least 4 hours and
  (2)  CPAP or IPPV for at least 4 hours and
  (3)  X-ray consistent with RDS
  (4)  RDS was considered resolved if the infant was in room air by day 10 of age and remained so until at least 28 days
  (5)  Occasional need for oxygen (<3 days) for procedures was allowed
 Classic bronchopulmonary dysplasia (BPD)
  (1)  Acute lung disease (RDS, pneumonia) which did not resolve and
  (2)  Continuous oxygen supplement for at least 28 days and
  (3)  X-ray consistent with BPD (as read by pediatric radiologist) at day 28 of age
 Atypical chronic lung disease (CLD)
  CLD after resolved RDS (CLDpRDS)
   (1)  Initial RDS that resolved by day 10and
   (2)  No oxygen supplement for at least 72 hours after resolution of RDS and
   (3)  Subsequent prolonged oxygen supplement continuing to at least day 28
  CLD without RDS: delayed CLD (DCLD)
   (1)  Absence of initial RDS and
   (2)  In room air until at least day 6 of ageand
   (3)  Subsequent persistent oxygen requirement past 28 days
  • Abbreviations: CPAP, continuous positive airway pressure; IPPV, intermittent positive pressure ventilation.