Fig. 1

Study design. a Phase 1. PEEP was reduced in steps of 2 cmH₂O from 15 to 5 cmH₂O every 10 min and finally in one step to ZEEP. b RM procedure in phase 1. VT was increased from 7 ml/kg in steps of 2 ml/kg, and each step was maintained for three breaths until the target airway pressure (40 cmH₂O) was achieved. c Phase 2. The traditional group was set with a VT of 9 ml/kg and the protective group with a VT of 7 ml/kg with optimal PEEP and RMs every 30 min. RM, recruitment maneuver; VT, tidal volume; PEEP, positive end-expiratory pressure; ZEEP, zero end-expiratory pressure; I, inspiratory; E, expiratory; R, respiratory rate