Effect of Inspired Oxygen Concentration on Postoperative Atelectasis After VATS Right Lobectomy

This study aims to investigate whether using 50% FiO₂ during one-lung ventilation, compared with 100% FiO₂, reduces postoperative atelectasis in the non-dependent (healthy) lung of patients undergoing VATS right pulmonary lobectomy, based on individualized PEEP titration. This is a single-center, prospective, assessor- and patient-blinded randomized controlled trial. A total of 100 patients (50 per group, including a pilot phase of 10 per group) will be enrolled and randomized 1:1 to the high-oxygen group (FiO₂=100%) and the low-oxygen group (FiO₂=50%). The primary endpoint is the percentage of atelectasis volume in the non-operated lung relative to the total non-operated lung volume, assessed by CT at 90±10 minutes postoperatively.

Inclusion Criteria: Age 18-65 years Elective thoracoscopic (VATS) right pulmonary lobectomy Anticipated one-lung ventilation duration \>1 hour ASA physical status I-III Exclusion Criteria: Previous lobectomy or lung volume reduction surgery Pre-existing significant atelectasis (large collapse on preoperative CT) Contraindications to PEEP: intracranial hypertension, bronchopleural fistula, hypovolemic shock, right heart failure, giant bullae, pneumothorax FiO₂ restrictions: preoperative continuous oxygen therapy or mechanical ventilation, moderate-severe COPD BMI ≥ 30 kg/m² Patient refusal to participate Withdrawal Criteria / Major Protocol Deviations: Surgery changed to simple wedge resection Severe pleural adhesions (found intraoperatively) Ventilation protocol interrupted Intraoperative blood loss \>500 ml Severe hypotension (MAP\