Impact of improved survival of very low-birth-weight infants on incidence and severity of bronchopulmonary dysplasia.

It has been suggested that improved survival of very low birth weight (VLBW) infants may have resulted in increased numbers of patients with bronchopulmonary dysplasia (BPD). To determine the impact of changes in mortality on the incidence and/or severity of BPD in three different time periods with distinct respiratory support strategies. Retrospective single center cohort study of VLBW infants: Cohort A (1986-1990): pre-surfactant era, use of conventional intermittent mandatory ventilation (IMV); cohort B (1993-1994): use of synthetic surfactant, nasopharyngeal continuous positive airway pressure (CPAP) and conventional IMV; cohort C (2000-2001): use of natural surfactant, early nasal prong CPAP, synchronized IMV with tidal volume monitoring and high frequency oscillatory ventilation (HFOV). BPD was classified as mild, moderate or severe according to Jobe and Bancalari. The median gestational ages and birth weights were 28 3/7 weeks and 1,120 g for cohort A (n = 97), 30 0/7 weeks and 1,340 g for cohort B (n = 100), and 29 1/7 weeks and 1,200 g for cohort C (n = 135). The use of partial or complete courses of antenatal corticosteroids (ANC) increased over time (58%, 72%, and 82%, p = 0.003). There was a 50% reduction of mortality between each time period with mortality rates of 30%, 14% and 7% in cohorts A, B and C, respectively (p < 0.001). The overall incidence of BPD was 26% in the pre-surfactant era, 11% during the mid-1990s and 19% in the most recent time period (r = -0.05, p = 0.36). Moderate and severe forms of BPD decreased over time and were seen in 11% in cohort A, 3% in cohort B and 2% in cohort C (p = 0.008). Changes in neonatal care of VLBW infants, including increased use of ANC and modified respiratory support strategies, have resulted in dramatically improved survival rates over the past 15 years without increasing moderate to severe pulmonary morbidity.