Fig. 4. Correlation between Pao2and fractional shunted blood flow (FQS) in the dependent region. The dashed curve represents the regression relation for all 10 data points (PaO2= 9.3 ×[FQS]−1.8). Symbols for each animal are as in figure 2. As shown by the arrows , in each animal, PaO2decreased and FQSin the dependent region increased from before (filled symbols ) to after (open symbols ) the recruitment maneuver. The lines connecting the individual data points corresponding to each animal have approximately the same slope as the dashed curve . This suggests that the effect of the recruitment maneuver PaO2could be largely explained by its effect on FQSin the dependent region.