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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).
Xavier et al. (Fri,) studied this question.