Optimal positive end-expiratory pressure obtained with titration of a fraction of inspiratory oxygen: a randomized controlled clinical trial

BACKGROUND: Optimal intraoperative positive end-expiratory pressure (PEEP) improves patient outcomes. Pulse oximetry has been used to determine the lung opening and closing pressures. Therefore, we hypothesized that intraoperative optimal PEEP obtained by titrating inspiratory oxygen fraction (FiO(2)) guided with pulse oximetry could improve perioperative oxygenation. METHODS: Forty-six males undergoing elective robotic-assisted laparoscopic prostatectomy were randomly assigned to either the optimal PEEP group (group O; n=23) or the fixed PEEP of 5 cmH(2)O group (group C; n=23). Optimal PEEP, defined as the PEEP with the lowest FiO(2) or 0.21 to maintain SpO(2) greater than or equal to 95%, was obtained in both groups after placing the patients in the Trendelenburg position and conducting intraperitoneal insufflation. Optimal PEEP was maintained for patients in group O. A PEEP of 5 cmH(2)O intraoperatively was maintained for patients in group C. Both groups were extubated in a semisitting position once the extubation criteria were met. The primary outcome was the arterial oxygen partial pressure (PaO(2)) divided by the inspiratory oxygen fraction (FiO(2)) prior to extubation. The secondary outcome was the incidence of postoperative hypoxemia (SpO(2) less than 92% on room air after extubation) in the postanesthesia care unit (PACU). RESULTS: The median optimal PEEP was 16 cmH(2)O (IQR 12–18). The PaO(2)/FiO(2) prior to extubation was significantly higher in group O than in group C (77.0±4.9 kPa vs. 60.6±5.9 kPa; P=0.04). PaO(2)/FiO(2) was also significantly higher in group O 30 minutes after extubation (57.6±1.9 vs. 46.6±1.8 kPa; P=0.01). The incidence of hypoxemia on room air in the PACU was significantly lower in group O than in group C (4.3% vs. 30.4%; P=0.02). CONCLUSIONS: Intraoperative optimal PEEP can be achieved by a titration of FiO(2) guided with SpO(2). Maintaining intraoperative optimal PEEP improves intraoperative oxygenation and reduces the incidence of postoperative hypoxemia. TRIAL REGISTRATION: The study was prospectively registered on September 10, 2021, in the Chinese Clinical Trial Registry (identifier: ChiCTR2100051010).