This study investigates how endotracheal tube (ETT) cuff pressure management during cardiopulmonary bypass (CPB) in coronary artery bypass grafting (CABG) affects upper airway edema. Patients will be randomized into two groups: cuff pressure kept at 0 mmHg or maintained at 20-30 mmHg during CPB. Ultrasonography will be used to measure lateral pharyngeal wall thickness, tongue parameters, and other airway dimensions at predefined perioperative time points. The primary outcome is the change in lateral pharyngeal wall thickness as an indicator of airway edema. A total of 76 patients aged 18-80 years undergoing elective CABG with CPB will be enrolled. The results aim to clarify safe cuff pressure management strategies to reduce airway edema.