Neonatal respiratory mechanics and development of bronchial hyperresponsiveness in preterm infants

BACKGROUND: In preterm ventilated infants, irreversible damage to the airway mucosa in the neonatal period might be related to the development of bronchial hyperresponsiveness (BHR) in subsequent years. AIMS: To evaluate whether neonatal indicators of long-term respiratory morbidity, respiratory system compliance (Crs) and resistance (Rrs), were causally related to bronchial responsiveness at the age of 2 and whether these relationships were affected by other factors. STUDY DESIGN: Mean neonatal Crs and Rrs of the first 3 days of life were assessed using the single breath occlusion technique. Bronchial challenge tests were performed at 2 years of age. When wheezing occurred during chest auscultation or oxygen saturation decreased below 90%, the provocative concentration of methacholine was recorded. SUBJECTS: Forty-five preterm infants of <37 weeks gestation, being mechanically ventilated within 24 h after birth. RESULTS: Decreased neonatal Crs was related to BHR (beta per ml/kPa, 0.061; 95% confidence interval, 0.019 to 0.103; p=0.006). Correction was required for radiological gradation of respiratory distress syndrome, the maximal peak inspiratory pressure required during mechanical ventilation and postnatal corticosteroid therapy. Neonatal Rrs, gestational age and birth weight were not related to subsequent BHR development. CONCLUSION: In ventilated preterm infants, decreased neonatal Crs was related to the development of BHR at the age of 2.