Lung Expansion Technics on Chest Wall Mechanics and Preventing Pulmonary Complication After Abdominal Surgery

The lung expansion techniques are widely used to prevent postoperative pulmonary complications. However, the effect of each technique on thoracoabdominal mechanics after abdominal surgery and if it influences the rate of postoperative pulmonary complications remains unknown. The investigators hypothesis is that the lung expansion technique that more increases lung volume after abdominal surgery, will be the most efficient in preventing postoperative pulmonary complication after abdominal surgery. The investigators objectives will be to compare the effect of different lung expansion techniques on lung volumes and activation of inspiratory muscle, and prevention of pulmonary complications in patients undergoing upper abdominal surgery. This study will involve 171 patients undergoing elective abdominal surgery. Patients will be randomly divided into 5 groups: no therapy group (n=35), continuous positive airway pressure (CPAP, n=34); volumetric incentive spirometry (VIS, n=34); flow oriented incentive spirometry (FIS, n=33) and deep breathing (DB, n=35). The thoracoabdominal mechanics will be assessed before and 3 days after surgery. Complications will be evaluated by a researcher who did not know to which group each patient belongs.