RT Journal Article SR Electronic T1 Prospective longitudinal measurements of N2 multiple breath washout indices in primary ciliary dyskinesia JF European Respiratory Journal JO Eur Respir J FD European Respiratory Society SP P4527 VO 44 IS Suppl 58 A1 Helene Kobbernagel A1 Kent Green A1 Astrid Madsen A1 Frederik Buchvald A1 Jakob Ejlertsen A1 Per Gustafsson A1 Kim Gjerum Nielsen YR 2014 UL http://erj.ersjournals.com/content/44/Suppl_58/P4527.abstract AB Background: Previous studies of multiple breath washout (MBW) indices (lung clearance index (LCI), Sacin*VT and Scond*VT) in primary ciliary dyskinesia (PCD) have demonstrated abnormal values in about 85%, 96% and 78%, respectively, - even with spirometric values within the normal range. Long term variability of N2 MBW indices in PCD has not been reported, although important for the use and interpretation of N2 MBW indices in the clinical management and as outcome measures in interventional studies.Aims and objectives: To assess the overall change in N2 MBW indices during one year and estimate the within- and between-occasion variability in PCD.Methods: N2 MBW (Exhalyzer D, Eco Medics AG) in triplets and standard spirometry were prospectively assessed on three occasions over one year. Occasions with less than two acceptable MBW measurements were excluded.Results: Twenty-six PCD patients, aged 6-18 years (median 12.8) performed 76 N2 MBW test occasions of which 72 (95%) were included. Baseline mean (SD) FEV1 % predicted: 84.8 (11.3); LCI: 9.8 (1.9); Sacin*VT: 0.15 (0.08); and Scond*VT: 0.06 (0.02). Within-occasion SD / CV% (95% CI) of LCI were 0.63 (0.55; 0.70) / 6.6% (6.0%; 7.2%). Scond*VT significantly improved over the study period.View this table: Conclusions: This study reports estimates of short- and long term variability of N2 MBW indices in a cohort of paediatric PCD patients, which is essential for future studies in PCD with MBW indices as outcome measures.