Fig. 4.
Regional strain estimates for the studied combinations of PEEP and VT levels. The x-axes shows strain values (dimensionless), and the y-axes shows eight ROIs from the most dependent (ROI 2) to the most nondependent (ROI 9). Regional specific volume change (εsVol) in blue demonstrated gravitational dependence with increased strain from nondependent to dependent ROIs, and decrease with increased PEEP. Regional-specific volume change corrected for tidal recruitment (εsVol,Rec, red) and tidal alveolar strain (εALV, black), while also showing gravitational dependence, presented maxima at middependent lung levels. εsVol,Rec decreased with PEEP, whereas εALV increased. For all VT-PEEP conditions, a significant difference was found between methods (P < 0.001), and between ROIs (P < 0.01). Data are shown as the mean ± SD.