Tracking pulmonary exacerbations in preschool children using the lung clearance index

Abstract

Background: The lung clearance index (LCI) derived from the multiple breath washout (MBW) test may be clinically useful to monitor children with cystic fibrosis (CF). Symptoms in preschool children are often due to intermittent viral infections that can affect both the upper and lower airways. Our objective was to investigate whether the LCI can detect changes associated with respiratory symptoms in both healthy preschool children and those with CF. Methods: Preschool children (2.5 to 6 years) from three centres (Toronto, Indianapolis & Chapel Hill) were evaluated at 6 study visits over 1 year. In addition to MBW (Exhalyzer D®, EcoMedics AG, Switzerland), current and past symptoms were recorded at each visit. A random-effects regression model was used to determine the association between pulmonary symptoms and changes in LCI over the 12 month period. Results: 147 subjects (71 healthy, 76 CF) were evaluated at 657 visits (338 healthy, 319 CF). During the study period, 43 episodes of pulmonary exacerbations (PEx) treated with oral antibiotics were reported in patients with CF, and 27 episodes of upper respiratory symptoms in healthy children. LCI was similar in healthy children regardless of respiratory symptoms (mean difference 0.1, 95% CI -0.33; 0.53), whereas in CF patients, LCI was significantly worse (0.6, 95% CI 0.00; 1.2) in patients with PEx. Conclusion: These findings confirm that LCI is sensitive to detect changes in lung function associated with PEx in preschool children with CF. The lack of effect of upper airway symptoms on LCI in healthy children is reassuring and suggests that changes observed in CF patients are likely due to worsening lower airway disease. Funded by the NHLBI.