Individualized positive end-expiratory pressure reduces driving pressure in obese patients during laparoscopic surgery under pneumoperitoneum: a randomized clinical trial.

Introduction: During pneumoperitoneum (PNP), airway driving pressure (ΔP _RS ) increases due to the stiffness of the chest wall and cephalic shift of the diaphragm, which favors atelectasis. In addition, depending on the mechanical power (MP) formulas, they may lead to different interpretations.
Methods: Patients >18 years of age with body mass index >35 kg/m ² were included in a single-center randomized controlled trial during their admission for bariatric surgery by abdominal laparoscopy. Intra-abdominal pressure was set at 15 mmHg at the pneumoperitoneum time point (PNP). After the recruitment maneuver, the lowest respiratory system elastance (E _RS ) was detected during the positive end-expiratory pressure (PEEP) step-wise decrement. Patients were randomized to the 1) CTRL group: ventilated with PEEP of 5 cmH ₂ O and 2) PEEP _IND group: ventilated with PEEP value associated with E _RS that is 5% higher than its lowest level. Respiratory system mechanics and mean arterial pressure (MAP) were assessed at the PNP, 5 min after randomization (T1), and at the end of the ventilation protocol (T2); arterial blood gas was assessed at PNP and T2. ΔP _RS was the primary outcome. Three MP formulas were used: MP _A , which computes static PEEP × volume, elastic, and resistive components; MP _B , which computes only the elastic component; and MP _C , which computes static PEEP × volume, elastic, and resistive components without inspiratory holds.
Results: Twenty-eight patients were assessed for eligibility: eight were not included and 20 patients were randomized and allocated to CTRL and PEEP _IND groups ( n = 10/group). The PEEP _IND ventilator strategy reduced ΔP _RS when compared with the CTRL group (PEEP _IND , 13 ± 2 cmH ₂ O; CTRL, 22 ± 4 cmH ₂ O; p < 0.001). Oxygenation improved in the PEEP _IND group when compared with the CTRL group ( p = 0.029), whereas MAP was comparable between the PEEP _IND and CTRL groups. At the end of surgery, MP _A and MP _B were correlated in both the CTRL (rho = 0.71, p = 0.019) and PEEP _IND (rho = 0.84, p = 0.020) groups but showed different bias (CTRL, -1.9 J/min; PEEP _IND , +10.0 J/min). At the end of the surgery, MP _A and MP _C were correlated in both the CTRL (rho = 0.71, p = 0.019) and PEEP _IND (rho = 0.84, p = 0.020) groups but showed different bias (CTRL, -1.9 J/min; PEEP _IND , +10.0 J/min).
Conclusion: Individualized PEEP was associated with a reduction in ΔP _RS and an improvement in oxygenation with comparable MAP. The MP, which solely computes the elastic component, better reflected the improvement in ΔP _RS observed in the individualized PEEP group.
Clinical Trial Registration: The protocol was registered at the Brazilian Registry of Clinical Trials (U1111-1220-7296).
Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The authors declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision.
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