<qa>  What is the purpose of this study?The purpose of this study is to determine whether Electrical Impedance Tomography can be used as sensitive and specific predictor in the detection of postoperative pulmonary complications e.g. pneumonia, bronchitis, acute respiratory distress syndrome, pleural effusion, pneumothorax, pulmonary edema, atelectasis, pulmonary embolism, hypoxemia, hypercapnia, spasms and obstructions of the airway in patients undergoing epigastric surgery. 