<i>In vitro</i> variability of functional residual capacity measurement.

<p><i>Bland Altman</i> plot <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036083#pone.0036083-Bland1" target="_blank">[16]</a> of measured functional residual capacity (FRC) minus lung model FRC plotted vs. mean of measured and model FRC. Differences (open circles), and mean difference, and upper and lower limits of agreement (mean difference ±1.96 SD of differences) are given as dashed lines for the small lung model and as solid lines for the large lung model. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036083#pone-0036083-g002" target="_blank">Figure 2a</a> gives absolute FRC differences (mL). For the small and large lung model, mean differences are −10.2 mL and 12.5 mL, upper limits of agreement are 9.9 mL and 121.9 mL, and lower limits of agreement are −30.3 mL and −96.8 mL, respectively. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036083#pone-0036083-g002" target="_blank">Figure 2b</a> gives relative FRC differences (%). For the small and large lung model, mean differences are −3.8% and 0.4%, upper limits of agreement are 3.6% and 4.7%, and lower limits of agreements are −11.2% and −4.0%, respectively.