The prevalence of obese patients in a great number of patients scheduled for elective surgery under general anesthesia has been on the increase. Recent studies suggest an intraoperative protective mechanical ventilation for the obese. Surgical procedures in the oral cavity increase the risk of perioperative complications of obese patients. By making this randomized clinical study, investigators want to determine whether the protective intraoperative ventilation with the use of higher positive end-expiratory pressure and recruitment maneuvers compared to ventilation with low positive end-expiratory pressure and without recruitments cause better postoperative respiratory function parameters of obese patients during oral surgical procedures. Investigators also aim to establish the fact which value of a positive end-expiratory pressure has a favorable impact on the respiratory function without negative hemodynamic effect.