Influence of intra-abdominal pressure and positive end-expiratory pressure on mixed venous oxygen saturation. Mixed venous oxygen saturation in % in function of different levels of intra-abdominal pressures (IAP) (3 mmHg (baseline), 18 mmHg (grade II intra-abdominal hypertension), and 26 mmHg (grade IV intra-abdominal hypertension)) at different levels of positive end-expiratory pressures (PEEP). Mean and SE are shown. ANOVA and post hoc Student-Newman-Keuls were used for statistical testing *, P < 0.05 within an IAP setting vs. the corresponding value at 5 cmH2O PEEP. #, P < 0.05 within a PEEP setting vs. the corresponding value at baseline IAP.