Do clinical markers of barotrauma and oxygen toxicity explain interhospital variation in rates of chronic lung disease?

Objective. To explore the hypothesis that variation in respiratory manageme nt among newborn intensive care units (NICUs) explains differences in chron ic lung disease (CLD) rates. Design. Case-cohort study. Setting. NICUs at 1 medical center in New York (Babies' and Children's Hosp ital [Babies']) and 2 in Boston (Beth Israel Hospital and Brigham and Women 's Hospital [Boston]). Study Population. Four hundred fifty-two infants born at 500 to 1500 g birt h weight between January 1991 and December 1993, who were enrolled in an ep idemiologic study of neonatal intracranial white matter disorders. Case Definition. Supplemental oxygen required at 36 weeks' postmenstrual ag e. Results. The prevalence rates of CLD differed substantially between the cen ters: 4% at Babies' and 22% at the 2 Boston hospitals, despite similar mort ality rates. Initial respiratory management at Boston was more likely than at Babies' to include mechanical ventilation (75% vs 29%) and surfactant tr eatment (45% vs 10%). Case and control infants at Babies' were more likely than were those at Boston to have higher partial pressure of carbon dioxide and lower pH values on arterial blood gases. However, measures of oxygenat ion and ventilator settings among case and control infants were similar at the 2 medical centers in time-oriented logistic regression analyses. In mul tivariate logistic regression analyses, the initiation of mechanical ventil ation was associated with increased risk of CLD: after adjusting for other potential confounding factors, the odds ratios for mechanical ventilation w ere 13.4 on day of birth, 9.6 on days 1 to 3, and 6.3 on days 4 to 7. Among ventilated infants, CLD risk was elevated for maximum peak inspiratory pre ssure >25 and maximum fraction of inspired oxygen = 1.0 on the day of birth , lowest peak inspiratory pressure >20 and maximum partial pressure of carb on dioxide >50 on days 1 to 3, and lowest white blood count <8 K on days 4 to 7. Even after adjusting for white blood count <8 K and the 4 respiratory care variables, infants in Boston continued to be at increased risk of CLD , compared with premature infants at Babies' Hospital. Conclusion. In multivariate analyses, a number of specific measures of resp iratory care practice during the first postnatal week were associated with the risk of a very low birth weight infant developing CLD. However, after a djusting for baseline risk, most of the increased risk of CLD among very lo w birth weight infants hospitalized at 2 Boston NICUs, compared with those at Babies' Hospital, was explained simply by the initiation of mechanical v entilation.