During general anaesthesia, pulmonary atelectasis has been shown to occur in 85 to 90% of patient. Pulmonary atelectasis increases occurrence of postoperative pulmonary complication including pneumoniae. Pulmonary atelectasis can be prevented or reversed by alveolar recruitment manoeuvres (ARM). Two methods for ARMs have been described. A sustained continuous positive airway pressure (CPAP) or a stepwise increase in PEEP.The transient increase in intrathoracic pressure during ARMs decreases venous return and increases pulmonary vascular resistance. This result in a decrease in right and left ventricular stroke volume (SV). Finally, the deleterious hemodynamic effects of ARMs may be exacerbated by hypovolemia, heart failure, and in patients with chronic treatment wich impedes cardiovascular responses to hypovolemia. At our best knowledge, there is no study which compared the hemodynamic effects of ARM using sustained CPAP or stepwise increase in PEEP. Consequently, the present study was designed to examine the hemodynamic effects of 2 ARM methods in anesthetized patients.