Radical operation of esophageal cancer is complicated and traumatic, and ventilation with one lung in lateral position and ventilation with both lungs after supine position requires long-term tracheal intubation and ventilator-assisted ventilation, and the incidence of postoperative pulmonary complications is high.

Therefore, we should explore the most appropriate lung protection ventilation strategy to reduce the occurrence of pulmonary complications. The recommended standard of international expert group on lung protective ventilation strategy points out that the lowest concentration of oxygen (≤40%) should be inhaled as much as possible during mechanical ventilation to maintain normal blood oxygen level (SpO2≥94%). If the mixed gas with low inhaled oxygen concentration can achieve ideal oxygen saturation and arterial oxygen partial pressure, it may reduce the postoperative pulmonary complications of the subjects. However, there are few reports on the influence of different oxygen concentrations on pulmonary complications in patients undergoing radical resection of esophageal cancer. This study intends to explore the influence of different oxygen concentrations on pulmonary complications in patients undergoing radical resection of esophageal cancer.

Inclusion Criteria:

• American Association of Anesthesiologists (ASA) patients with I-II physical condition;
• Patients with preoperative partial pressure of blood gas and oxygen greater than 80mmHg who were scheduled for elective esophageal cancer surgery were operated in the right lateral position first and then in the supine position.

Exclusion Criteria:

• there is a history of acute lung injury with acute respiratory distress syndrome within three months;
• Heart failure (classified by new york Heart Association) is greater than grade IV,
• there is a serious liver and kidney dysfunction (children with grade B or C liver failure, glomerular filtration rate < 30 ml/min);
• Body mass index > 30kg/m2；
• coagulation dysfunction;
• Operation time exceeds 10h
• The amount of bleeding is more than 800ml, and the total fluid volume is more than 3000ml.