EPS04.1 Longitudinal changes in lung clearance index in children with CF

Abstract

Lung clearance index (LCI), a marker of gas mixing efficiency, is a promising parameter to assess lung function in patients with CF. In cross-sectional data, LCI is often abnormal, even in subjects with normal FEV 1 . Few data are available on long-term evolution of LCI. Objectives LCI was measured prospectively in children with CF during routine follow-up. Changes in LCI were evaluated after 2 years, to explore the magnitude of changes and the relation with changes in FEV 1 . Methods LCI was measured with the Ecomedics Exhalyzer D, using a N 2 washout. Spirometry was performed at the same visit. An LCI higher than 8.3 and a FEV 1 Z-score lower than 1.97 were considered abnormal. Results In 42 patients with a median age of 12.2 years (range 5.8 to 17.2), two measurements were compared with median interval of 21 months (range 18 to 27). At first timepoint (T1), median LCI was 9.4 (range 6.0 to 14.5) and median FEV1 Z-score –0.6 (range –4.1 to 2.0). Over the observation period, individual changes in both parameters occurred, but on the whole major changes were unusual: FEV1 Z-score was normal but LCI was abnormal at T 1 in 23 patients, and this remained so at T2 in 21; both FEV 1 and LCI were normal at T1 in 12 patients, this remained so at T2 in 11; both FEV 1 Z-score and LCI were abnormal at T1 in 7 patients, and this remained so at T 2 in 6. Abnormal FEV 1 and normal LCI was never seen. Conclusion In 23/42 children with CF, FEV1 z-score was normal but LCI z score was abnormal and this remained so 2 years later in all but two subject. These data further support the notion that measuring LCI brings additional information especially in the group of children with normal FEV 1 .