Ventilation distribution assessed by electrical impedance tomography during robot-assisted laparoscopic prostatectomy: A randomized controlled trial

During robot-assisted laparoscopic prostatectomy (RALP), the combination of intra-abdominal pressure and a steep Trendelenburg position increases the risk of alveolar collapse and shifts the center of ventilation toward the abdomen, leading to intraoperative and postoperative hypoxia. This study evaluated whether fixed positive end-expiratory pressure(PEEP) 10 cmH2O, compared with zero PEEP (ZEEP), maintained a more central ventilation distribution during RALP as assessed by electrical impedance tomography (EIT).

Sixty-five adult patients undergoing RALP were randomly assigned to either a PEEP 0 cmH2O group or a PEEP 10 cmH2O group. The primary endpoint was the mean center of ventilation (COV), as assessed using EIT. Secondary endpoints included other EIT parameters: the region of interest, global inhomogeneity index, and regional ventilation delay, as well as the P/F ratio, pulmonary compliance, peak airway pressure, and driving pressure (ΔP). Hemodynamic effects, lung injury biomarkers, and inflammatory cytokines were also evaluated. EIT and ventilator parameters were recorded at 6 time points: pre-intubation, post-intubation, during the Trendelenburg position, during pneumoperitoneum, pre-extubation, and post-extubation. Arterial blood gas and hemodynamic data were collected at the same points, plus 4 hours after ICU admission and again at ICU discharge. Lung injury biomarkers and inflammatory cytokines were measured pre- and postoperatively.

The group-by-time interaction for COV was not statistically significant (P = .057). In exploratory Tukey-adjusted comparisons, COV was closer to 50% in the PEEP 10 group after intubation (PEEP 0 vs PEEP 10: 58.2% vs 53.4%; P = .038) and before extubation (58.6% vs 53.1%; P = .007). ΔP was lower, and lung compliance was higher, in the PEEP 10 group during the Trendelenburg position and pneumoperitoneum. No improvement in the P/F ratio or consistent between-group differences in major hemodynamic variables, KL-6, or IL-6 were observed.

During RALP, with a fixed PEEP of 10 cmH2O, there was no group-by-time interaction effect observed for COV. However, in exploratory time-point comparisons, it was associated with a tendency for ventilation to be more centrically shifted after intubation and before extubation, and was also associated with an attenuated increase in ΔP and an attenuated decrease in lung compliance during the Trendelenburg position and pneumoperitoneum.