Heterogeneous use of multiple breath washout in cystic fibrosis across age groups and European countries: an ECFSPR analysis

Multiple breath washout (MBW) and its primary output, lung clearance index (LCI), sensitively measure ventilation inhomogeneity in cystic fibrosis (CF). This study aimed to characterize real-world MBW use in Europe through retrospective analysis of 2023 data from the European Cystic Fibrosis Society Patient Registry (ECFSPR). We determined the proportions of people with (pwCF) with one MBW measurement in 2023 by age group, lung function, country and device used. We analysed data from 39,986 non-transplanted paediatric and adult pwCF from 40 countries. Overall, 10 % of pwCF had an MBW measurement in 2023. MBW was performed in 22 countries and in 12 % of pwCF in those countries. Austria had the highest overall MBW use (39 % of pwCF). The highest proportions of pwCF who had MBW were aged 6-11 years (23 %) and 12-17 years (23 %). MBW was mostly used in pwCF with normal (19 %) or mildly impaired (10 %) percent predicted forced expiratory volume in one second. The Eco Medics Exhalyzer® D N2 was the most commonly used device (83 %). MBW is not yet routinely used in CF care in many European countries, presenting a window of opportunity to standardise MBW devices, software, and data quality control processes. This will ensure the accuracy and reliability of LCI measurements across different centres and devices, and facilitate MBW implementation in research and in care.