Oxygen reserve index-based positive end-expiratory pressure allocation and end-of-surgery lung ultrasound findings during robot-assisted laparoscopic prostatectomy: a prospective randomized controlled trial

Pneumoperitoneum and steep Trendelenburg positioning during robot-assisted laparoscopic prostatectomy (RALP) promote lung derecruitment. We evaluated whether a prespecified oxygen reserve index (ORI)-based positive end-expiratory pressure (PEEP) allocation strategy reduced the study-specific unweighted total count of positive lung ultrasound (LUS) sign–region observations compared with fixed PEEP of 5 cmH 2 O. In this prospective randomized trial, 64 adults undergoing RALP were assigned 1:1 to fixed PEEP of 5 cmH 2 O or ORI-based PEEP. Baseline ORI was measured after induction under a fraction of inspired oxygen (FiO 2 ) of 0.5, before pneumoperitoneum and recruitment. Post-recruitment PEEP was assigned as follows: ORI > 0.40, PEEP 5 cmH 2 O; 0.20 < ORI ≤ 0.40, PEEP 8 cmH 2 O; and ORI ≤ 0.20, PEEP 10 cmH 2 O. Blinded LUS assessment was performed at baseline and the end of surgery. The co-primary outcomes were total positive LUS finding counts in the left and right hemithoraces at the end of surgery. Sixty-two patients (31 per group) were analyzed. At the end of surgery, observed mean total positive LUS finding counts for fixed versus ORI-based PEEP were 8.39 ± 1.82 versus 3.23 ± 1.52 in the left hemithorax and 7.74 ± 1.63 versus 3.32 ± 1.74 in the right hemithorax, yielding unadjusted differences (ORI-based minus fixed PEEP) of − 5.16 and − 4.42 findings, respectively. Corresponding adjusted differences were − 5.30 findings (95% CI, − 6.20 – −4.39) and − 4.40 findings (95% CI, − 5.31 – −3.49), respectively; both P < 0.001. Adjusted differences in baseline-to-end-of-surgery change were − 5.68 findings (95% CI, − 6.53 – −4.82) and − 5.36 findings (95% CI, − 6.28 – −4.43), respectively; both P < 0.001. ORI-based PEEP allocation was associated with lower end-of-surgery total positive LUS finding counts than fixed PEEP of 5 cmH 2 O. These proof-of-concept findings require validation against fixed moderate or higher PEEP in trials using patient-centered postoperative outcomes as primary endpoints. Clinical Research Information Service (KCT0010096).