In this randomized controlled trial, we aim to investigate whether the avoidance of mechanical ventilation by application of nonintubated thoracoscopic surgery improves intraoperative cerebral oxygenation and postoperative cognition recovery for patients undergoing thoracic surgery.

Postoperative neurocognitive impairment is not uncommon for patients undergoing thoracic surgery. Based on the literature, this is associated with reduced cerebral oxygenation during one-lung ventilation which may be because of reduced cardiac output, impeded cerebral venous return due to mechanical ventilation. In our hospital, nonintubated thoracoscopic surgery is commonly conducted and achieves noninferior outcomes than intubated thoracoscopic surgery. Particularly, the application of nasal high flow oxygen may maintain intraoperative oxygenation despite the absence of controlled ventilation. Therefore, the nonintubated technique may be beneficial to maintain an improved intraoperative cerebral oxygenation and hopefully improves postoperative cognition recovery. In this randomized controlled study, we aim to investigate the differences in intraoperative cerebral oxygenation and postoperative cognitive recovery bewteen nonintubated and intubated thoracoscopic surgery. Patient will be randomly assigned to receive nonintubated or intubated thoracoscopic surgery. During surgery, bifrontal cerebral oxygenation will be monitored. Cognitive test will be arranged before and after surgery.

Inclusion criteria:

Adult patients receive elective thoracoscopic surgery

Exclusion criteria:

1. pregnancy
2. preexisting cerebral dysfunction such as cerebral vascular incidence, Alzheimer's Disease. Parkinsonism.
3. Cardiopulmonary dysfunction such as heart failure > New York Heart Association score III; chronic obstructive pulmonary disease with a forced expiratory volume in one second/forced vital capacity < 70 % and FEV1 < 50% predicted.