Fig. 4

Decremental PEEP trials: identification of “best PEEP”. PEEP trials with decrements of 2 from 24 to 6 cmH₂O were performed at three instances following a recruitment maneuver (RM) in anesthetized pigs which had undergone combined lavage-induced surfactant depletion and therapeutic ventilation. Group A, N = 6: continuous automated protective low tidal volume ventilation (LV_T). Group B, N = 6: 3 h of injurious high tidal volume ventilation (HV_T) prior to PEEP trial 2, resumption of protective low tidal volume ventilation for 3 h prior to PEEP trial 3. Two animals died after injurious HV_T and RM 2, i.e., Group B, N = 4 at PEEP trial 2 and 3. For experimental protocol, see Fig. 1 and “Methods” Section. Line graphs depict the group means of C_rs and P_aO₂ obtained at each PEEP level. PEEP values at the maximum mean C_rs and maximum mean P_aO₂ (red vertical dotted lines) are consistently disparate within each group and differ between groups. Adjacent scatter plots depict the PEEP values at maximum C_rs and P_aO₂ of each individual animal and the means ± SD thereof. *p < 0.05, **p < 0.01, Mann–Whitney U test