RT Journal Article SR Electronic T1 One size does not fit all - Impact of the one liter tidal volume breathing protocol on indices from nitrogen multiple-breath washout in children JF European Respiratory Journal JO Eur Respir J FD European Respiratory Society SP P1441 VO 40 IS Suppl 56 A1 Sophie Yammine A1 Florian Singer A1 Philipp Latzin YR 2012 UL http://erj.ersjournals.com/content/40/Suppl_56/P1441.abstract AB Background Nitrogen multiple-breath washout (N2MBW) is a useful tidal breathing lung function test to assess ventilation inhomogeneity (VI), e.g. in Cystic Fibrosis (CF) patients. One liter tidal volume (VT) breathing protocols are regarded to improve comparability of results between subjects breathing at different VT and are widely used in adults. The impact of protocols using fixed VT on results in children is unknown. We assessed whether breathing at fixed VT impacts N2MBW indices in school-aged children.Methods Ten children with CF and 16 healthy children performed six N2MBW tests using a validated setup (Exhalyzer D, Eco Medics, Switzerland). Children performed three baseline N2MBW at free tidal breathing and three N2MBW at increased VT with a target of one liter using an incentive. Outcomes were size and variability of lung clearance index (LCI), functional residual capacity (FRC), Scond and Sacin.Results All 26 children achieved six N2MBW. Mean (SD) VT at free tidal breathing was 0.5 (0.1) L, at fixed VT 1.2 (0.2) L. Comparing free tidal breathing with the one liter VT N2MBW, LCI increased on average (95% CI) 2.3 (0.6-3.9) in CF children and 1.4 (0.5-2.3) in healthy children. LCI increased by more than one LCI unit in 9 out of 10 CF children and in 14 out of 16 healthy children. FRC decreased, Scond and Sacin increased significantly. Variability within tests and between subjects increased for all MBW outcomes.Conclusion Fixed tidal breathing protocols impact N2MBW indices as shown for the one liter VT protocol in school-aged children. Underlying physiological mechanisms and applicability in adult patients require further study.