PT - JOURNAL ARTICLE AU - Florian Singer AU - Sophie Yammine AU - Chiara Abbas AU - Markus Roos AU - Philipp Latzin TI - Ways to shorten the lung clearance index measurement ΙΙ - How long to wash? DP - 2012 Sep 01 TA - European Respiratory Journal PG - 3298 VI - 40 IP - Suppl 56 4099 - http://erj.ersjournals.com/content/40/Suppl_56/3298.short 4100 - http://erj.ersjournals.com/content/40/Suppl_56/3298.full SO - Eur Respir J2012 Sep 01; 40 AB - Background Inert gas multiple-breath washout (MBW) derived lung clearance index (LCI) is a sensitive lung function parameter in subjects with mild cystic fibrosis (CF) lung disease, but rarely measured in clinical routine due to lack of available equipment and lengthy protocols. Using an available nitrogen (N2) MBW setup (Exhalyzer D, Eco Medics, Switzerland), we assessed shortened N2MBW protocols for LCI.Methods Thirty-three school-aged children with CF and 21 controls performed triplicate N2MBW measurements. LCI was calculated as cumulative expired volume over functional residual capacity determined during N2MBW at 9% (1/11th) and 2.5% (1/40th, the current standard) end-tidal N2 concentration.Results LCI differed significantly between healthy and CF children at both concentrations. The 9%-LCI was modestly associated with final 2.5%-LCI (R2 = 0.7) but took less time and was of similar diagnostic value. Comparing 9%- and 2.5%-LCI, mean (SD) test duration was 1.0 (0.4) and 2.2 (1.0) min; mean (95%CI) area under the receiver operating characteristic curve was 0.9 (0.8-0.9) and 0.9 (0.8-0.9); and upper limits of normal LCI (4.5 and 8.4) correctly classified 72% and 74% of children, respectively. Mean (SD) coefficient of variation was 5.7 (3.9)% for 9%-LCI and 5.7 (3.2)% for 2.5%-LCI.Conclusion LCI determined at 9% end-tidal N2 concentration during N2MBW is repeatable, considerably faster, and identifies early CF lung disease with similar diagnostic value compared to the standard LCI in the current study population. This new shortened N2MBW protocol seems promising for time-saving LCI measurement in clinical routine.