EPS04.3 Comparison of CF and non-CF LCI results using the Exhalyzer D and Innocor™ devices

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Background Multiple breath washout (MBW) is a pulmonary function test that allows measurement of lung clearance index (LCI), a marker of ventilation heterogeneity. LCI is increasingly being considered as a clinical trial outcome measure. The Exhalyzer D N 2 washout (N 2 /ExD, Ecomedics AG, Switzerland) is the recommended technique by the ECFS CTN. Mostly our group's experience with LCI uses the Innocor™ gas analyser (Innovision, Denmark), SF6 as a tracer gas (SF6/Inn). To understand the N 2 /ExD technique, the aims of this study were to compare (a) intra-test variability; (b) LCI values, (c) LCI & FEV1 for the two techniques. Methods 21 CF (14F, mean 20±12 yrs) and 10 non-CF (8F, mean 28±10 yrs) have completed MBW trials with the 2 techniques in random order on the same visit; methods previously described (Horsley et al. 2009, Jensen et al. 2013). Results Intra-test CoV (2–3repeats) was similar for SF 6 /Inn and N 2 /ExD (3.57 vs 3.78 CF, ns). LCI was significantly higher with N 2 /ExD than with SF 6 /Inn in both CF (14.05 vs 9.33; p≤0.0001) and non-CF (7.08 vs 6.64, p=0.04). Both techniques show a significant correlation for LCI and FEV 1 %, although the regression slopes were significantly different (p = 0.005); much steeper for N 2 /ExD. Conclusions LCI values cannot be used interchangeably between the Innocor™ and Exhalyzer D. In non CF, there was a statistically significant difference, with higher values in the N 2 /ExD. The difference was much greater in CF and increased as LCI did. In the context of similar intra-test variability, the hypothesis that this may translate into improved power in future clinical trials needs to be tested. Sponsored by a non-restricted grant from Novartis.