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).

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

Background Individualized positive end-expiratory pressure (PEEP) combined with recruitment maneuvers improves intraoperative oxygenation in individuals undergoing robot-assisted prostatectomy. However, whether electrical impedance tomography (EIT)-guided individualized PEEP without recruitment maneuvers could also improve intraoperative oxygenation is unknown. Methods Fifty-six male patients undergoing elective robotic assisted laparoscopic prostatectomy were randomly assigned to either individualized PEEP (Group PEEPIND, n = 28) or control with fixed PEEP of 5 cmH2O (Group PEEP5, n = 28). Individualized PEEP was guided by EIT after placing the patients in Trendelenburg position and intraperitoneal insufflation. Patients in Group PEEPIND maintained the individualized PEEP without intermittent recruitment maneuvers and those in Group PEEP5 maintained PEEP of 5 cmH2O intraoperatively. Both groups were extubated in a semi-sitting position once the extubation criteria was met. The primary outcome was the arterial oxygen partial pressure (PaO2) / inspiratory oxygen fraction (FiO2) prior to extubation. Other outcomes included intraoperative driving pressure, plateau pressure and dynamic respiratory system compliance, and the incidence of postoperative hypoxemia in post-operative care unit (PACU). Results The intraoperative median PEEPIND was 16 cmH2O (ranging from 12 to18 cmH2O). EIT-guided PEEPIND was associated with higher PaO2/FiO2 before extubation compared to PEEP5 (71.6 ± 10.7 vs. 56.8 ± 14.1, P = 0.003). The improved oxygenation extended into the PACU with lower incidence of postoperative hypoxemia (3.8% vs. 26.9%, P = 0.021). Additionally, PEEPIND was associated with lower driving pressures (12.0 ± 3.0 vs. 15.0 ± 4.4 cmH2O, P = 0.044) and better compliance (44.5 ± 12.8 vs. 33.6 ± 9.1 ml/cmH2O, P = 0.017). Conclusion Individualized PEEP guided by EIT without intraoperative recruitment maneuvers improved perioperative oxygenation in patients undergoing robot-assisted laparoscopic radical prostatectomy. Trial registration: China Clinical Trial Registration Center Identifier: ChiCTR2100053839. Registered 01/12/2021. First patient recruited on 15/12/2021. http://www.chictr.org.cn/showproj.aspx?proj=141373.