Effects of Different Inhalation Oxygen Concentrations on Postoperative Atelectasis

This study was a single-center, prospective, randomized controlled, two-arm study. This study will be conducted in the First Hospital of China Medical University. the investigators aimed to investigate the effects of different inspired oxygen concentrations in lung protective ventilation strategies on immediate postoperative atelectasis and intraoperative changes of oxygenation index in patients undergoing neurosurgical surgery in the supine position.

Inclusion Criteria:patients with American Society of Anesthesiologist (ASA) physical status I-II;Older than 18 years; Patients with operation time more than 2 hours and plan to extubate in the operating room;Preoperative blood gas partial pressure of oxygen was more than 80mmHg;Patients scheduled for elective neurosurgery were operated in the supine position.Exclusion Criteria:A history of acute lung injury with acute respiratory distress syndrome within three months;Heart failure (New York Heart Association class) greater than IV, severe liver and kidney dysfunction (Child B or C liver failure, glomerular filtration rate <30ml/min);BMI > 30 kg/m2.The operation time is more than 10 hours;The amount of bleeding was more than 500ml; The total fluid volume exceeded 3000ml.