EIT-guided end-expiratory pressure individualization in robotic surgery with high PEEP ventilation: a prospective observational study

Pneumoperitoneum and extreme positioning during robotic surgery impose substantial mechanical load on the respiratory system. Whether bedside electrical impedance tomography (EIT) is beneficial for individualized positive end-expiratory pressure (PEEP) titration under routinely high-PEEP ventilation remains uncertain. We assessed the feasibility and benefits of EIT-guided PEEP titration during clinical routine and explored whether pre-EIT respiratory parameters or anthropometric variables can predict EIT-guided best PEEP and EIT endpoints: lung collapse reduction, overdistention reduction, and regional ventilation delay reduction in routine perioperative care. Prospective observational study in 177 patients undergoing elective robotic procedures spanning steep Trendelenburg (e.g., prostate/rectal) and non-Trendelenburg (e.g., adrenalectomy) positions with a laparoscopic pressure of 20 cmH2O. After establishing pneumoperitoneum and final positioning, EIT (OD–CL crossing-point method) was used to titrate PEEP. Primary endpoints were EIT-guided best PEEP and change in PEEP. Secondary endpoints were change in dynamic compliance (Cdyn), driving pressure (DP), and mechanical power (MP) normalized to Cdyn (MPadj), as well as EIT-derived endpoints: lung collapse reduction, overdistention reduction, and regional ventilation delay reduction. Associations between pre-EIT variables and outcomes were tested by correlations and ROC analysis. For the primary endpoints, EIT-guided PEEP increased pre-EIT PEEP from 12.0 ± 2.0 to 14.8 ± 2.1 cmH2O and, hence, by 2.8 ± 2.3 cmH2O. Of the secondary endpoints, Cdyn improved in 82% of the patients after EIT-guided PEEP titration. DP lowered in 31% of the patients, with post-EIT DP of ≤ 15 cmH2O. Despite mechanical gains, MPadj increased on average from 0.42 to 0.43 J·cmH2​O·min−1ml−1. Concerning the EIT-derived endpoints, lung collapse reduction was 88%, overdistention reduction was 12%, and regional ventilation delay reduction was 30%. Proportions in secondary endpoints did not differ across surgical subgroups. Baseline anthropometrics showed poor predictive value for EIT-guided best PEEP (strongest correlation with MPadj: r = 0.33, R2 = 0.109) and change in PEEP (strongest correlation with the difference between laparoscopic pressure and PEEP (lap. pressure-PEEP), r = 0.38; R2 = 0.144). Pre-EIT Cdyn best signalled lung collapse reduction with an ROC-derived cutoff < 45.75 ml/H2O (accuracy 0.82, sensitivity 0.84, specificity 0.68). EIT-guided PEEP titration improved ventilation parameters in a heterogeneous robotic cohort with high abdominal pressure subject to high-PEEP, maintaining lung-protective ventilation. Pre-EIT respiratory data and anthropometric variables were insufficient for the reliable prediction of EIT-guided best PEEP. Our study demonstrates that EIT can be implemented in clinical routine and allows for individualization of respiratory treatment during robotic surgery, subject to high-PEEP ventilation. Not applicable.