Thoracoscopic surgery is the most common surgical approach in thoracic surgery, which reduces surgical trauma and postoperative pain compared with open thoracotomy, but postoperative complications should not be overlooked, with hypoxemia being particularly prominent. Postoperative hypoxemia is highly prevalent among patients recovering from non-cardiac surgery, accounting for over one-third of all cases. Hypoxemia impairs wound healing and leads to other severe complications such as cerebral dysfunction, arrhythmia, and myocardial ischemia, all of which adversely affect postoperative recovery. Although oxygen therapy can prevent and treat hypoxemia, many patients still experience hypoxia in the post-anesthesia care unit (PACU). Numerous studies have investigated various ventilation techniques aimed at enhancing postoperative pulmonary function, but the benefits of protective ventilation strategies may be lost during emergence from anesthesia. Several other studies also indicate that intraoperative ventilation measures do not improve postoperative pulmonary function. The lack of evidence demonstrating the efficacy of oxygen therapy or protective ventilation techniques in treating postoperative hypoxemia underscores the need to explore alternative strategies. Patient positioning during emergence from anesthesia is associated with perioperative and postoperative complications. Although no consensus exists on the optimal patient position during emergence, the supine position is often favored by anesthesiologists due to its simplicity and ease of monitoring. However, the reduced functional residual capacity associated with the supine position tends to promote airway closure and diminish gas exchange.

Thoracoscopic surgery is the most common surgical approach in thoracic surgery, which reduces surgical trauma and postoperative pain compared with open thoracotomy, but postoperative complications should not be overlooked, with hypoxemia being particularly prominent. Postoperative hypoxemia is highly prevalent among patients recovering from non-cardiac surgery, accounting for over one-third of all cases. Hypoxemia impairs wound healing and leads to other severe complications such as cerebral dysfunction, arrhythmia, and myocardial ischemia, all of which adversely affect postoperative recovery. Although oxygen therapy can prevent and treat hypoxemia, many patients still experience hypoxia in the post-anesthesia care unit (PACU). Numerous studies have investigated various ventilation techniques aimed at enhancing postoperative pulmonary function, but the benefits of protective ventilation strategies may be lost during emergence from anesthesia. Several other studies also indicate that intraoperative ventilation measures do not improve postoperative pulmonary function. The lack of evidence demonstrating the efficacy of oxygen therapy or protective ventilation techniques in treating postoperative hypoxemia underscores the need to explore alternative strategies. Patient positioning during emergence from anesthesia is associated with perioperative and postoperative complications. Although no consensus exists on the optimal patient position during emergence, the supine position is often favored by anesthesiologists due to its simplicity and ease of monitoring. However, the reduced functional residual capacity associated with the supine position tends to promote airway closure and diminish gas exchange. In contrast, the semi-recumbent position (SRP) has been shown to increase vital capacity by 10% to 15%, enhance functional lung volume and residual capacity, and improve diaphragmatic range of motion, thereby promoting lung expansion and gas exchange. Currently, only one study has found that in patients undergoing laparoscopic-assisted upper abdominal surgery, 30° SRP during anesthesia recovery can reduce the incidence of postoperative hypoxemia. Therefore, we conducted this real-world study to test the efficacy and optimal tilt angle of SRP in reducing hypoxemia during anesthesia recovery in a large sample of patients undergoing thoracoscopic surgery.

Inclusion Criteria:

• Age 18-85 years old; Undergo thoracoscopic segment/lobectomy; American Society of Anesthesiologists (ASA) grade 1~3

Exclusion Criteria:

• Patients with mental or cognitive dysfunction who cannot communicate normally; Patients with tracheal catheters retained in ICU; Patients with cervical spondylosis, ankylosing spondylitis and other patients who cannot lift their upper body; Patients who have participated in other clinical trials; Patients who refuse to sign informed consent; Patients who have had chest surgery in the past.

Patients undergoing thoracoscopic lobectomy and segmental resection