Atrial fibrillation (AF) has been reported to occur in up to 20-40% of patients undergoing coronary artery bypass grafting (CABG). Postoperative AF plays a major role in the determination of hemodynamic deterioration and can be associated with thromboembolic stroke. Aside from the risk factors of age, pain, cardiac dysfunction and hypokalemia, hypoxemia is also considered to be the major contributor to AF initiation and persistence. Aiming to the common postoperative complications, noninvasive positive pressure ventilation (NIV) provides an available modality to improve the oxygen and even obviate the reintubation.~However, some patients are contraindications for NIV, with Loss of consciousness, hemodynamic instability, and some are intolerance due to dryness, gastric distension, skin breakdown and noise, with complaints of insomnia and sleep disturbance. The aforementioned factors largely limits its use. Recently, the heated humidified high-flow nasal cannula (HFNC), free of psychic stress and physical discomfort, shows a favorable compliance and tolerance in treating the hypoxemic patients. As a result, in this comfortable setting we predict a high sleep quality in HFNC oxygen therapy. Evidence has suggested that sleep abnormalities trigger the cascaded release of C-reactive protein (CRP). As is well known that CRP is involved in atrial structural remodeling and asynchronous conduction, which attribute to the initiation and maintenance of AF.~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.
The investigators hypothesized that heated humidified high-flow nasal cannula oxygen(HFNC) along with high quality of sleep, in comparison with noninvasive positive pressure ventilation (NIV), could reduce the release of inflammatory marker C-reactive protein(CRP), which as independent predictor of atrial fibrillation（AF）, further lower the incidence of new-onset AF following coronary artery bypass grafting(CABG).