Recruitment Maneuvers and PEEP-guided Electrical Impedance Tomography for Abdominal Laparoscopic Surgery Patients

The individualized high PEEP with RMs group commences with a PEEP of 5 cm H2O and undergo an RM followed by a decremental PEEP trial. Pressure-controlled ventilation mode is set with a respiratory rate of 16 breaths per minute and ΔP=15 (ΔP is calculated by subtracting PEEP from the plateau pressure (Pplat). In intervals of 5 breaths, PEEP is incrementally increased by 5 cm H2O, starting at 5 cm H2O and reaching up to 20 cm H2O. The decremental PEEP trial is immediately performed following the first RM, beginning at a PEEP of 20 cm H2O with a respiratory rate of 15 breaths per minute. Every 30 seconds, PEEP is decreased by increments of 2 cm H2O until it reaches a minimum of 6 cm H2O. This decremental PEEP trial is succeeded by a second RM, after which the individualized PEEP level will be established as determined by the decremental PEEP trial and sustained until the completion of ventilation.

Ventilation is set in volume-controlled mode with a tidal volume of 7 ml/kg predicted body weight (PBW), the respiratory rate is adjusted to target normocapnia (end-tidal carbon dioxide partial pressure between 35 and 45 mmH), an inspiratory to expiratory ratio of 1:2, and a PEEP of 5 cmH2O.