EIT-Guided Personalized PEEP Improves Postoperative Lung Ultrasound Scores in Patients Undergoing Metabolic Bariatric Surgery: A Randomized Controlled Trial

BACKGROUND: Postoperative pulmonary complications (PPCs) are prevalent after metabolic bariatric surgery (MBS) (Ann Surg 242:326–341, 2005, Best Pract Res Clin Anaesthesiol 24:211-25, 2010). Positive end-expiratory pressure (PEEP) is a cornerstone of lung-protective ventilation (Anesthesiology 123:66–78, 2015), but the optimal approach for titrating PEEP in patients with obesity is unknown (Trials 18:202, 2017). Electrical impedance tomography (EIT) enables individualized, real-time PEEP selection (Intensive Care Med 35:1132-7, 2009, Thorax 72:83–93, 2017). However, the influence of an EIT-based personalized PEEP strategy on early postoperative lung aeration, as quantified by the lung ultrasound score (LUS), remains incompletely characterized. METHODS: In this single-center, randomized controlled trial, we enrolled 120 patients scheduled for MBS. Participants were randomly assigned to receive either EIT-guided personalized PEEP (n = 60) or standard PEEP of 5 cmH2O (n = 60). The primary outcome was the change in LUS score from preoperative baseline (24 h prior to surgery) to post-extubation assessment (30 min following extubation, prior to PACU discharge). Secondary outcomes included respiratory mechanics intraoperatively, oxygenation index, and PPCS incidence within 48 h. RESULTS: Baseline characteristics, including preoperative oxygenation index, were well-balanced between the two groups (all P > 0.05). The median [IQR] PEEP level in the experimental group was 10 (Anesthesiology 111:979-87, 2009, Br J Anaesth 114:483–90, 2015) cmH2O. The EIT-guided group showed a greater improvement in LUS score compared with the fixed PEEP group (1.68 ± 1.02 vs. 1.25 ± 1.01; between-group mean difference: 0.43; 95% CI, 0.06 to 0.80; t = 2.162; P = 0.033). Furthermore, the EIT-guided group demonstrated a higher postoperative oxygenation index (407.58 ± 25.68 vs. 393.15 ± 30.21 mmHg; t = 2.820; P = 0.006) and greater dynamic lung compliance (revealing a significant main effect of group and a group-by-time interaction; P < 0.05). The effect size for the primary outcome was moderate (Cohen’s d = 0.395; 95% CI, 0.033 to 0.755). A sensitivity analysis using the Mann-Whitney U test confirmed the robustness of this primary finding (p = 0.031). There were no significant differences in PPCs incidence in the first 48 h or in hemodynamic safety parameters. CONCLUSION: In patients undergoing MBS, an EIT-based personalized PEEP strategy produces a statistically significant and clinically meaningful improvement in early postoperative lung aeration and respiratory function. This is evidenced by superior changes in LUS score, oxygenation index, and dynamic compliance without any reduction in hemodynamic safety when compared with 5 cmH2O of fixed PEEP. However, no significant difference was observed in the incidence of postoperative pulmonary complications within 48 h.