Influence of Moderate Inspired Oxygen Fraction (FiO2) and Protective Ventilation on Postoperative Pulmonary Complication

Inclusion Criteria: * ASA 1\~2,Planned intrabdominal hepatic resection surgery; * Expected duration 2 hours to 6 hours; * Age 40 yr to 70 yr); * BMI 18-26.9kg/m2 * Risk of postoperative pulmonary complications (Arozullah score ≥2); Exclusion Criteria: * Noninvasive ventilation in the last 30 days; * Recent history of pneumonia, ALI/ARDS (in the last 30 days); * History of pulmonary resection; * History of neuromuscular disease; * Child-Pugh\>A grade； * Patient refusal;