Nitrogen multiple-breath washout outcomes and variability.

<p>Triplicate nitrogen multiple-breath washout (N₂MBW) tests applied to measure functional residual capacity (FRC) <i>in vitro</i> in the small^* (n = 7) and the large^† lung model (n = 41), and in 30 healthy adults^‡. LCI = lung clearance index. S_acin = phase III slope index of <i>acinar</i> ventilation inhomogeneity. S_cond = phase III slope index of conductive ventilation inhomogeneity. CV = intra-test coefficient of variation (SD/mean*100). Mean difference^§ (95% confidence interval) from paired <i>t</i>-tests comparing measured and actual model FRC [<i>in vitro</i>] or N₂MBW outcomes between two test occasions [<i>in vivo</i>]. CR = coefficient of repeatability (1.96*SD of differences between measured and actual model FRC or differences of N₂MBW outcomes between tests). CR is given in respective units or as percentage of the mean. n.a. = not applicable.