Effect of Control Ventilation, PEEP, and PEEP With ARM in Robot-assisted Radical Prostatectomy

In the ARM group, alveolar recruitment maneuvers were performed three times at predefined time points after pneumoperitoneum and Trendelenburg positioning: 40 minutes (T2), 70 minutes (T3), and 110 minutes (T4) after pneumoperitoneum. ARM was conducted using a stepwise increase in PEEP with a maximum peak inspiratory pressure of 40 cmH₂O: PEEP was increased from 4 to 8 cmH₂O for 3 breaths, from 8 to 12 cmH₂O for 3 breaths, and from 12 to 16 cmH₂O for 10 breaths.

Sample size calculation was based on data obtained from a pilot study, using the PaO₂/FiO₂ ratio as the primary outcome for comparison among the three groups. Assuming an effect size of 0.25, a statistical power of 0.80, and a two-sided significance level of 0.05, a total sample size of 48 patients was required. To account for a potential dropout rate of 20%, a total of 60 patients were enrolled in the study.

Repeated measurements of PaO₂/FiO₂ ratio and other longitudinal variables will be analyzed using repeated-measures analysis of variance or generalized estimating equations, as appropriate. A p-value <0.05 will be considered statistically significant. Statistical analyses will be performed using SPSS version 30 (IBM Corp., Armonk, NY, USA).

Inclusion criteria

• Adult patients with American Society of Anesthesiologists (ASA) physical status I-III scheduled for elective robot-assisted radical prostatectomy under general anesthesia

Exclusion criteria

• uncontrolled asthma, chronic obstructive pulmonary disease (defined as a forced expiratory volume in 1 second to forced vital capacity ratio <60% or forced expiratory volume in 1 second <60% of the predicted value)
• hypoxemia (oxygen saturation <90% on room air)
• left ventricular ejection fraction <50%
• hypotension (systolic blood pressure <90 mmHg)
• body mass index ≥30 kg/m²
• conversion to open surgery, or intraoperative events that precluded protocolized ventilation.