Influence of lung injury and PEEP on VRI V_T measurement: ANCOVA.

Slopes and intercepts for the different measurement points (BLH: baseline healthy; ALI-0: impaired lungs (ALI) at zero PEEP; ALI-5: ALI at PEEP 5 mbar; ALI-10: ALI at PEEP 10 mbar; ALI-15: ALI at PEEP 15 mbar) are presented on the left. Descriptive measures of the differences in VT measured by VRI and EIT, displayed as mean±SD (standard deviation) and range [ml] are presented on the right. To investigate the influence of lung damage and PEEP on EIT and VRI VT measures, an ANCOVA was used to test the equality of slopes and intercepts (using an F test to compare a global model where slope is shared among the data sets, with a model where each dataset gets its own slope). The first P-value tested the null hypothesis that the slopes are all identical (the lines are parallel). The second P-value represents the results of testing the null hypothesis that the intercepts are identical.