Individual positive end-expiratory pressure settings optimize intraoperative mechanical ventilation and reduce postoperative atelectasis

Background: Intraoperative lung-protective ventilation has been recommended to reduce postoperative pulmonary complications after abdominal surgery. Although the protective role of a more physiologic tidal volume has been established, the added protection a?orded by positive end-expiratory pressure (PEEP) remains uncertain. Te authors hypothesized that a low fxed PEEP might not ft all patients and that an individually titrated PEEP during anesthesia might improve lung function during and after surgery. Methods: Forty patients were studied in the operating room (20 laparoscopic and 20 open-abdominal). Tey underwent elective abdominal surgery and were randomized to institutional PEEP (4cm H₂O) or electrical impedance tomography-guided PEEP (applied after recruitment maneuvers and targeted at minimizing lung collapse and hyperdistension, simultaneously). Patients were extubated without changing selected PEEP or fractional inspired oxygen tension while under anesthesia and submitted to chest computed tomography after extubation. Our primary goal was to individually identify the electrical impedance tomography-guided PEEP value producing the best compromise of lung collapse and hyperdistention. Results: Electrical impedance tomography-guided PEEP varied markedly across individuals (median, 12cm H₂O; range, 6 to 16cm H₂O; 95% CI, 10-14). Compared with PEEP of 4cm H₂O, patients randomized to the electrical impedance tomography-guided strategy had less postoperative atelectasis (6.2±4.1 vs. 10.8±7.1% of lung tissue mass; P = 0.017) and lower intraoperative driving pressures (mean values during surgery of 8.0±1.7 vs. 11.6±3.8cm H₂O; P < 0.001). Te electrical impedance tomography-guided PEEP arm had higher intraoperative oxygenation (435±62 vs. 266±76 mmHg for laparoscopic group; P < 0.001), while presenting equivalent hemodynamics (mean arterial pressure during surgery of 80±14 vs. 78±15 mmHg; P = 0.821). Conclusions: PEEP requirements vary widely among patients receiving protective tidal volumes during anesthesia for abdominal surgery. Individualized PEEP settings could reduce postoperative atelectasis (measured by computed tomography) while improving intraoperative oxygenation and driving pressures, causing minimum side e?ects.