Chronic lung disease in extremely low birth weight infants: a two-year retrospective analysis.

To determine the incidence and classification of chronic lung disease (CLD) in extremely low birth weight (ELBW) infants, a 2-year retrospective analysis was performed. From January 1997 to December 1998, 117 infants weighing less than 1000 g were enrolled. The survival rate beyond 28 days was 60.7% (71/117). CLD was defined as a supplemental oxygen requirement at 28 days of age, with symptoms of persistent respiratory distress and chest radiograph showing characteristic appearance. In addition to the common finding of CLD, infants with bronchopulmonary dysplasia (BPD) had history of respiratory distress syndrome (RDS), infants with Wilson-Mikity syndrome (WMS) had no RDS but had early appearance of bubbly lung on chest x-ray, and infants with chronic pulmonary insufficiency of prematurity (CPIP) had only hazy appearance on chest x-ray. The incidence of CLD in infants who survived beyond 28 days was 50.7% (36/71). Among the 36 infants with CLD, 17 (47%) had BPD, 4 (11%) had WMS and 15 (42%) had CPIP. The median (min, max) days of mechanical ventilation were 45 (9, 112), 45.5 (45, 50) and 7.5 (0, 40) days in BPD, WMS and CPIP groups, respectively. The median (min, max) days of oxygen requirement were 73 (28, 120), 149 (70, 211) and 52.5 (38, 90) days, respectively. The infants still requiring oxygen at post-conceptional age of 36 weeks are significantly more in BPD (14 (82.4%)) and in WMS (4 (100%)) than in CPIP (3 (20%)). Two (1 BPD, 1 WMS) were discharged and received oxygen therapy at home. Four infants with BPD died of respiratory failure. CLD includes a wide range of conditions, from BPD or WMS with severe respiratory morbidity and mortality to no residual problems. Such information is important for design of appropriate strategies to prevent CLD.