Respiratory Function at 6 weeks of age is associated with the development of bronchiolitis in infants born to mothers with asthma during pregnancy

Background: Infants born to asthmatic mothers have higher risk of bronchiolitis and inflammometry (eNO)-guided asthma management during pregnancy reduced parent-reported bronchiolitis episodes at 12 months of age (Mattes et al Thorax 2013). The mechanisms for this effect are unknown. Objective: To test for an association between infant lung function at 6 weeks of age and the development of bronchiolitis in the first 6 months of life in a cohort of babies born to women with asthma during pregnancy. Methods: We performed tidal breathing volume loop (TBVL) measurements during quiet sleep in infants born to mother with asthma who participated in an ongoing multi-centre RCT of eNO-guided asthma management vs usual care, focussing on perinatal outcomes (Breathing for Life Trial). Results: 262 babies were recruited to date, 229 attended a clinical assessment, and 204 remained in quiet sleep during testing. 171 TBVL procedure were attempted (47% female; age 6 weeks, SD 1.3), 149 (87%) tests were technically acceptable. At the time of abstract submission, 107 were 6 months old and 34 of these infants had at least one episode of bronchiolitis and their mean PTEF/TE at 6 weeks of age was 27.49 (SD 7.2; 95% confidence interval [CI] 25.1 to 29.9). In infants who had not developed bronchiolitis, mean PTEF/TE was 32.26 (SD 9.5; 95% CI 30.3 to 33.2). Conclusion: These preliminary results suggest that lung function in early life affects bronchiolitis risk and that the preventative effect of eNO-guided asthma management during pregnancy on bronchiolitis could be associated with higher PTEF/TE.