Patients submitted to general anesthesia and mechanical ventilation commonly develop pulmonary atelectasis, which can cause adverse consequences either intraoperatively or postoperatively. The use of lower, more physiological tidal volumes (6-8 mL/Kg of ideal body weight) during the intraoperative period can minimize the risk of lung injury but may be associated with increased atelectasis. The application of PEEP can prevent the formation of atelectasis and minimize the resulting complications, but at the present time, there is no consensus on how to tailor the level of PEEP to best suit each patient.