Abstract: Objective To investigate the association of lung stress index (SI) during one-lung ventilation with postoperative hypoxemia in patients undergoing lobectomy. Methods The prospective cohort study was conducted from July 1, 2022, to December 31, 2022, at the Affiliated Hospital of Southwest Medical University, involving patients undergoing video-assisted thoracoscopic surgery for pulmonary lobectomy. All patients received double-lumen endotracheal tube intubation, lung-protective ventilation strategy, PEEP incremental lung recruitment maneuver, and synchronized intermittent mandatory ventilation during anesthetic emergency. Total intravenous anesthesia was adopted for maintenance. Patients were grouped into low SI, medium SI, and high SI groups according to the mean values of SI recorded within the first 5 minutes during one-lung ventilation (0.9, 0.9 to 1.1, 1.1, respectively). The primary outcome was the occurrence of hypoxemia from postoperative day 1 to day 5 or at discharge, while the secondary outcome was the proportion of lung aeration compartments on the non-operative side. Results A total of 72 patients were finally entered into the analysis. The incidence of postoperative hypoxemia was 66.7% (24/36) in the low SI group, 38.1% (8/21) in the medium SI group, and 26.7% (4/15) in the high SI group, with a significantly higher incidence in the low SI group (P=0.029). The risk of postoperative hypoxemia was associated with age, preoperative oxygen saturation, duration of one-lung ventilation, lung compliance, inspiratory resistance, airway pressure, mechanical power, and SI, with a 30% decrease in risk for every 0.1 increase in SI. The proportion of hyper-aerated lung compartments was greater in patients with high SI, both preoperatively and postoperatively, while the proportion of atelectasis compartment was higher in patients who suffered postoperative hypoxemia. Conclusion Lower SI during one-lung ventilation was associated with a higher incidence of postoperative hypoxemia. Ventilation strategies aimed at maintaining SI at a medium level may reduce the risk of postoperative hypoxemia in patients undergoing thoracic surgery.
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