Comparison of the optimal PEEP determined with the GI index, dynamic compliance and compliance-volume curve method. Left = box plot. The boxes mark the quartiles while the whiskers extend from the box out to the most extreme data value within 1.5 times the interquartile range of the sample. Middle = Bland-Altman plot comparing global inhomogeneity (GI) and dynamic compliance method (Cdyn). Right = Bland-Altman plot comparing GI and the intra-tidal compliance-volume curve calculated by the SLICE method (C_V). The numbers above the * indicate the number of overlapping results. The dashed line at the middle depicts the mean value of the whole data set. The other two dashed lines represent mean ± 1.96 times standard deviation.