Optimal Positive End-Expiratory Pressure Obtained with Titration of Fraction of Inspiratory Oxygen: A Randomized Controlled Clinical Trial

Abstract

Background Optimal intraoperative positive end expiratory pressure (PEEP) improves patient outcomes. The 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 (FiO2) guided with pulse-oximetry could improve perioperative oxygenation. Methods Forty-six males undergoing elective robotic assisted laparoscopic prostatectomy were randomly assigned to either optimal PEEP (Group O, n=23) or control with fixed PEEP of 5 cmH2O (Group C, n=23). Optimal PEEP, defined as the PEEP with lowest FiO2 or 0.21 to maintain SpO2≥ 95%, was obtained in both groups after placing the patients in Trendelenburg position and peritoneal insufflation. Patients in Group O maintained the optimal PEEP and in Group C maintained PEEP of 5cmH2O intraoperatively. Both groups were extubated in a sitting position once the extubation criteria met. The primary outcome was the partial arterial oxygen pressure (PaO2)/inspiratory oxygen fraction (FiO2) prior to extubation. Secondary outcome was the incidence of postoperative hypoxemia (SpO2༜92% on room-air after extubation) in post-operative care unit. Results The median optimal PEEP was 16 cm H2O [inter-quartile range, 12-18]. The PaO2/FiO2prior to extubation was significantly higher in Group O than that in Group C (77.0±4.9kPa vs.60.6±5.9kPa, p=0.04); PaO2/FiO2 was also significantly higher in Group O 30minutes after extubation (57.6±1.9 vs. 46.6±1.8kPa, p=0.01). The incidence of hypoxemia on room air in the post-operative care unit was significantly lower in the Group O than in the Group C (1/23, or 4.3% vs. 7/23 or 30.4%, p =0.02). Conclusions Intraoperative optimal PEEP can be achieved by titration of FiO2 guided with SpO2. Maintaining intraoperative optimal PEEP improves intraoperative oxygenation and reduces the incidence of post-operative hypoxemia. Trial registration : Chinese Clinical Trial Registry identifier: ChiCTR2100051010. Prospectively registered on 10 September, 2021