Effect of Sevoflurane and Remimazolam on Arterial Oxygenation During One-lung Ventilation

Inclusion Criteria: * Patients undergoing video-assisted thoracoscopic surgery * 19 years of age or older, less than 80 years old * The American Society of Anesthesiologists (ASA) classification I-Ⅲ physical status Exclusion Criteria: * Patients with known allergy to benzodiazepine, propofol * Patients with galactose intolerance, Lapp lactase deficiency, glucose-galactose malabsorption * Patients with hypersensitivity to Dextran40 * Patients with end stage renal disease requiring hemodialysis * Patients with history of acute angle glaucoma * Emergency operation * Patients with unstable hemodynamics requiring inotropics * Patients with preoperative oxygen supplement * Preoperative forced expiratory volume (FEV1) less than 40% of predicted * Preoperative ejection fraction less than 50%