Baseline respiratory mechanics parameters (driving pressure [DP], dynamic lung compliance [Cdyn]) and hemodynamic parameters (mean arterial pressure [MAP], SV, CO, CI) were recorded before ARM. Ten minutes after insufflation of the peritoneum with CO2 and positioning of the patient for surgery, an ARM was performed using the built-in protocol of the Mindray anesthesia machine, applying a continuous positive pressure of 30 cmH2O for 30 seconds. Immediately afterwards, the PEEP level was adjusted to 0 cmH2O. Respiratory and hemodynamic parameters were recorded at 5, 10, 15, 20, 25, 30, 35, and 40 minutes after ARM. The PEEP level was set back to 4 cmH2O forty minutes after ARM until the end of surgery.

Baseline respiratory mechanics parameters (driving pressure [DP], dynamic lung compliance [Cdyn]) and hemodynamic parameters (mean arterial pressure [MAP], SV, CO, CI) were recorded before ARM. Ten minutes after insufflation of the peritoneum with CO2 and positioning of the patient for surgery, an ARM was performed using the built-in protocol of the Mindray anesthesia machine, applying a continuous positive pressure of 30 cmH2O for 30 seconds. Immediately afterwards, the PEEP level was adjusted to 4 cmH2O. Respiratory and hemodynamic parameters were recorded at 5, 10, 15, 20, 25, 30, 35, and 40 minutes after ARM. The PEEP level was set back to 4 cmH2O forty minutes after ARM until the end of surgery.

Baseline respiratory mechanics parameters (driving pressure [DP], dynamic lung compliance [Cdyn]) and hemodynamic parameters (mean arterial pressure [MAP], SV, CO, CI) were recorded before ARM. Ten minutes after insufflation of the peritoneum with CO2 and positioning of the patient for surgery, an ARM was performed using the built-in protocol of the Mindray anesthesia machine, applying a continuous positive pressure of 30 cmH2O for 30 seconds. Immediately afterwards, the PEEP level was adjusted to 8 cmH2O. Respiratory and hemodynamic parameters were recorded at 5, 10, 15, 20, 25, 30, 35, and 40 minutes after ARM. The PEEP level was set back to 4 cmH2O forty minutes after ARM until the end of surgery.

After the patient enters the operating room, routine monitoring of ECG, non-invasive blood pressure, and SpO₂ is performed. Local anesthesia is used for radial artery puncture and catheterization to monitor invasive blood pressure.

After 3 minutes of pre-oxygenation, tracheal intubation is performed with the following ventilation parameters: VT 6-8 ml/kg, FiO₂ 60%, RR 15 breaths/min, I/E 1:2, and PEEP 4 cmH₂O. Ten minutes after the establishment of pneumoperitoneum during surgery, baseline levels of respiratory mechanical parameters and hemodynamic variables are recorded. Subsequently, alveolar recruitment is performed at a pressure of 30 cmH₂O for 30 seconds. Immediately after recruitment, the PEEP level is adjusted according to the group. The changes in respiratory mechanics parameters and hemodynamic variables after recruitment are recorded. After the outcome indicators recover to the new baseline level, the PEEP is readjusted to 4 cmH₂O.