The effect of inspired oxygen concentration on postoperative pulmonary atelectasis in obese patients undergoing laparoscopic cholecystectomy: a randomized-controlled double-blind study

Introduction Atelectasis is the most important postoperative pulmonary complication in obese patients following general anaesthesia. The study aimed to determine the effect of inspired high versus low oxygen concentration on pulmonary atelectasis in obese patients undergoing laparoscopic cholecystectomy. Patients and methods A total of 60 patients, American Society of Anesthesiologists I–II, of both sexes, aged 20–60 years, BMI more than 30 kg/m2 and scheduled for elective laparoscopic cholecystectomy were randomly assigned to group I inspired 40% oxygen and group II inspired 90% oxygen after endotracheal intubation and for 2 h postoperatively. The effect of inspired oxygen concentration on atelectasis approved by computed tomographic scan and radiography was determined 24 h after surgery. Oxygen saturation, the partial pressure of arterial oxygen and carbon dioxide, tension, pulmonary functions and haemodynamic parameters were also recorded. Results Atelectasis was detected by computed tomography scans of the chest performed in the first postoperative day in 60% of patients in group I, whereas it was detected in 76.7% of patients in group II without significant difference between the groups, and it was determined in 33% of patients in group I compared with 46% of patients in group II, without significant difference between the two groups by radiographic examination. Postoperative forced vital capacity and forced expiratory volume in 1 s were significantly reduced in the two groups compared with the preoperative values in both groups without significant difference between the two groups. The intraoperative partial pressure of arterial oxygen values showed an insignificant change in the postoperative measurements between the groups. Conclusion Administration of low percentage of oxygen concentration (40%) was associated with decreased incidence of atelectasis without worsening of pulmonary function.