Background: pulmonary complications after cardiac surgery recorded incidence of 25% of all cardiac surgeries. Ventilation strategies before and after CPB also cause problems. Alveolar over-distention and reduced lung recruitment are involved in lung injury during general anesthesia in cardiac surgeries. Protective lung ventilation is a common practice during general anesthesia and includes positive end expiratory pressure (PEEP), recruitment maneuvers and the use of FiO2 levels not greater than 80%. Aim of the Work: the aim of the study was to compare the effect of application of continuous positive airway pressure (C-PAP) ventilation during cardiopulmonary bypass and application of positive end expiratory pressure (PEEP) after cardiopulmonary bypass (CPB) per se or followed by lung recruitment (RM) in the intensive care unit (ICU) on arterial oxygenation after cardiopulmonary bypass. Patients and Methods: after obtaining approval from the medical ethical committee, this study was conducted at Cardiothoracic Academy of Ain Shams University and Ain Shams University specialized hospitals. The study included 66 patients divided into three equal groups. Conclusion: the application of alveolar recruitment strategy showed short term improvement in the arterial oxygenation and ventilation perfusion mismatch in patients undergoing CABG using CPB. Further studies are needed to determine if this beneficial effect of recruitment maneuvers could be further prolonged and produce more lasting clinical effects.