EIT-guided PEEP Titration Versus Standard Ventilation in Bariatric Surgery

"The Recruitment Maneuver - PEEP Titration - Recruitment Maneuver (RM-T-R) Strategy" will be implemented 5 minutes after endotracheal intubation. The patient will receive an RM (peak pressure 50cm H2O, PEEP 25cmH2O, respiratory rate 6 bpm, for 10 cycles) followed by a decremental PEEP titration, during which PEEP is set to 25cm H2O and decreased stepwise by 2cm H2O every 3min until reaching 5 cmH₂O. Meanwhile, the ventilator parameters (tidal volume, respiratory rate, and inspiratory-to-expiratory ratio) will be adjusted back to their pre-recruitment settings. EIT-based optimal PEEP is defined as the crossing point of the overdistension and collapse curves during a decremental PEEP trial.

In group p-8, mechanical ventilation will be administered in volume-controlled mode with a tidal volume of 8 ml/kg (based on ideal body weight). Additional settings include a PEEP of 8 cmH₂O, FiO₂ of 0.5, an inspiratory-to-expiratory ratio of 1:2, and a respiratory rate of 12 breaths/min. A recruitment maneuver (RM) will be performed 5 minutes after intubation and again after surgery, using the same protocol as in group P-eit. The respiratory rate will be adjusted as needed to maintain end-tidal CO₂ between 35 and 45 mmHg throughout the procedure.