Despite the availability of surfactant treatment, extremely low birth weight (ELBW) infants continue to be at high risk of developing bronchopulmonray dysplasia (BPD). Evidence suggests that pathologic changes occur within the first few days of life. We hypothesized that the changes in early respiratory system compliance and resistance in ELBW infants with or without hyaline membrane disease (HMD) would correlate with BPD severity and aid in its prediction. Respiratory system compliance (Crs) and resistance (Rrs) were measured at the end of weeks 1, 2, 3, and 4 in 46 infants weighing 1,000 g or less at birth, using the single breath airway occlusion method. Twenty-four infants had HMD and 22 did not. Fifteen infants with and 10 infants without HMD developed BPD with radiological changes and oxygen needs at 28 days. Twelve BPD infants required supplemental oxygen beyond 36 weeks, defined as chronic lung disease (CLD). Irrespective of whether the infant initially had HMD, the week 1 results showed that infants who subsequently developed BPD had a significantly higher respiratory system resistance than those who did not (P = 0.0014). Though week 1 compliance was lower, it was not statistical significant. Multiple logistic models consisting of simple neonatal variables and week 1 respiratory mechanics showed that Rrs was independently associated with subsequent BPD (P = 0.026) and CLD (P = 0.016), while compliance was not. Prediction of CLD improved with the inclusion of Rrs results as compared to prediction using clinical variables alone. Throughout the 4-week study period, Rrs was significantly higher in BPD infants than in those without BPD, and resistance was particularly abnormal in those who had CLD or subsequently required corticosteroid treatment. These observations provide rationale for interventions to prevent BPD within the first week of life. Respiratory mechanics measurements could be useful in the assessment of therapeutics in the current surfactant era.
Copyright 2000 Wiley-Liss, Inc.