Contemporary N and SF Multiple Breath Washout in Infants and Toddlers with Cystic Fibrosis

Introduction: Multiple breath washout (MBW) is used for early detection of cystic fibrosis (CF) lung disease, with SF MBW commonly viewed as the reference method. The use of N MBW in infants and toddlers has been questioned for technical and physiological reasons, but a new correction of the N signal has minimized the technical part. The present study aimed to assess the remaining differences and the contributing mechanisms for the differences between SF and N MBW,corrected-such as tidal volume reduction during N washout with pure O .

Method: This was a longitudinal multicenter cohort study. SF MBW and N MBW were performed prospectively at three CF centers in the same visits on 154 test occasions across 62 children with CF (mean age: 22.7 months). Offline analysis using identical algorithms to the commercially available program provided outcomes of N and N for comparison with SF MBW.

Results: Mean functional residual capacity, FRC was 14.3% lower than FRC , and 1.0% different from FRC . Lung clearance index, LCI was 25.2% lower than LCI , and 7.3% higher than LCI . Mean (SD) tidal volume decreased significantly during N MBW , compared to SF MBW (-13.1 ml [-30.7; 4.6], p < 0.0001, equal to -12.0% [-25.7; 1.73]), but this tidal volume reduction did not correlate to the differences between LCI and LCI . The absolute differences in LCI increased significantly with higher LCI (0.63/LCI ) and (0.23/LCI ), respectively, for N and N , but the relative differences were stable across disease severity for N , but not for N .

Conclusion: Only minor residual differences between FRC and FRC remained to show that the two methods measure gas volumes very similar in this age range. Small differences in LCI were found. Tidal volume reduction during N MBW did not affect differences. The corrected N MBW can now be used with confidence in young children with CF, although not interchangeably with SF .