Background. Atrial fibrillation is one of the most common complications in the postoperative period of coronary artery bypass grafting (CABG) surgery and usually associated with increased length of hospital stay and higher hospital costs. Among the main mechanisms involved, excessive sympathetic activation, oxidative stress and inflammation are fundamental elements in the pathophysiology of obstructive sleep apnea. Objectives. To evaluate the effects of continuous positive airway pressure (CPAP) in reduction of atrial fibrillation after CABG in patients with obstructive sleep apnea. Methodological procedures: A multicenter randomized controlled study to compare the incidence of atrial fibrillation between the intervention group and the control group, both monitored seven days with Holter.