Ultrasound guided individualized PEEP reduces postoperative atelectasis in elderly patients undergoing laparoscopic radical rectal cancer surgery

Older patients undergoing laparoscopic radical rectal cancer surgery under general anesthesia with mechanical ventilation face an increased risk of postoperative pulmonary atelectasis due to the Trendelenburg position and pneumoperitoneum. This study aims to assess whether lung ultrasound-guided individualized positive end-expiratory pressure(PEEP) ventilation can reduce postoperative atelectasis in older patients. Forty patients aged > 65 years scheduled for elective laparoscopic radical rectal cancer surgery were randomly assigned to two groups: the ultrasound-guided group (Group P) received individualized PEEP titrated by lung ultrasound, and the control group (Group C) maintained a fixed PEEP of 5 cmH₂O. PEEP was maintained until extubation in both groups. Post-extubation, lung ultrasound assessed 12 regions in both lungs. Ultrasound-guided individualized PEEP values varied significantly between individuals [median (IQR): 11 (7-11.75) ]. Compared with the PEEP with a fixed 5 cmH₂O, the incidence of postoperative pulmonary atelectasis (postoperative day 1: 0 vs. 25%; P = 0.047) and severity [lung ultrasound score (LUS):8.5 (6-9.75) vs. 12.5 (10-13.75); P < 0.001)] were lower in the patients undergoing the lung ultrasound PEEP titration strategy. Meanwhile, the intraoperative drive pressure(ΔP) (6.5 ± 2.8 vs. 10.4 ± 5.8; P = 0.01) and the incidence of postoperative pulmonary complications(PPCs) (5% vs. 35%; P = 0.044) were lower in the ultrasound-guided group, and intraoperative oxygenation index(OI) (461.5 ± 39.5 vs. 415.7 ± 69.1; P = 0.014) and dynamic compliance(Cdyn) (36.4 ± 8.2 vs. 25.8 ± 8.9; P < 0.001) were elevated. The perioperative hemodynamic characteristics were comparable between the two groups. Lung ultrasound-guided individualized PEEP decreased the incidence and severity of postoperative atelectasis in older patients undergoing laparoscopic rectal cancer surgery. This strategy improved intraoperative respiratory mechanics (Cdyn, ΔP, OI) and reduced PPCs without hemodynamic compromise.Trial registration This clinical trial was registered at the Chinese Clinical Trial Registry (Registration No.:ChiCTR2300078385, 07/12/2023, www.chictr.org.cn ).