Titration of Inspired Oxygen to Decrease the Incidence of Postoperative Pulmonary Complications

Inclusion Criteria: * ① General anesthesia with left bronchial tube intubation; ② Age range from 18 to 80 years old; ③ 18 kg/m2 ≤ BMI ≤ 30 kg/m2; ④ ASA grade I to III; ⑤ Individuals willing to participate in research and sign an informed consent form. Exclusion Criteria: * ① CT scan indicates preoperative pulmonary infection, atelectasis, and pneumothorax; ② History of respiratory system diseases (COPD, bronchiectasis, pulmonary alveoli, interstitial lung disease, etc.); ③ Previous history of lung surgery; ④ First second forced expiratory volume/estimated value (FEV1%)\<60%; ⑤ PaO2\<60mmhg (1 mmhg=0.133 kpa) or PaO2/FiO2\<300mmhg or SpO2\<90% in the suction state; ⑥ History of acute upper respiratory tract infection, acute lung injury, acute respiratory distress syndrome, or respiratory failure within 3 months prior to surgery; ⑦ Combined heart failure (NYHA heart function grading ≥ 3); ⑧ Previous history of stroke and cerebral infarction; ⑨ Severe liver dysfunction (liver failure or Child Pugh score B or C) Chronic renal failure (glomerular filtration rate\<30 ml/min) Suffering from mental illness, etc., which is not suitable for the author; æ Individuals who have participated in other clinical trials as subjects within the three months prior to participating in the study The patient refused to participate in the study.