A novel method for infant multiple breath washout: first report in clinical practice

Background: Lung clearance index (LCI), measured using multiple breath inert gas washout (MBW) is a potentially useful test in infants with respiratory disease, particularly cystic fibrosis (CF). Clinical use is limited however by the need for specialist staff and equipment. We have previously described a novel method for infant MBW suitable for use outside of specialist laboratories. This study describes its performance in vivo in infants with CF and healthy controls, including a limited comparison with the respiratory mass spectrometer. Methods: Children aged <2 years with CF and controls underwent MBW testing on a single occasion. Practical applicability of the system was determined by the number of successful duplicate tests, and within-subject repeatability. Results: 25 children (7 with CF, 18 healthy controls, all sedated with chloral hydrate) attempted MBW. 20 patients (7 with CF) successfully underwent duplicate testing (80% success rate). Mean within-subject coefficient of variation for FRC was 7.2% and for LCI 5.9%. Comparison of LCI with the mass spectrometer was limited, but gave very similar values for LCI and FRC in those patients who underwent technically adequate tests with both methods. Conclusions: We have described a new MBW method that is feasible and reproducible in sedated infants. Results fall within the expected range, and well within accuracy limits set by international guidelines.This could provide a more accessible alternative to previously described systems for infant MBW, and overcomes many of the technical challenges inherent in conventional MBW.