<qa>  What is the purpose of the study?Anesthesia-induced atelectasis persist in the postoperative period but are not usually diagnosed because imaging techniques are required. The aim of the study is to determine whether the value of SpO296 while breathing room air 0.21 FiO2 for 5 min, maneuver that we defined as the Air Test, was able to diagnose atelectasis in the postoperative period after a general anesthesia. 