Therefore, in this present study, the investigators first evaluate the sleep quality (architecture and duration) by the polysomnographic (PSG) monitoring after coronary surgery. Based on the sleep parameters, the investigators hypothesize that HFNC, along with high quality of sleep, in comparison with NIV, could reduce the release of C-reactive protein, which as independent predictor of atrial fibrillation (AF), further lower the incidence of new-onset AF following CABG.