This study focuses on CPAP non-adherent patients. It evaluates the upper airway collapsibility in awake and two different sedative levels, BIS 65-75 (light sedation) and BIS 50-60(deep sedation). Conscious sedation will be achieved by propofol pump infusion. No benzodiazepam or opioid are used to avoid the effect of upper airway muscle tone and respiratory drive. The patency over the velopharynx, oropharynx, larynx, and hypopharynx will be recorded. Specific obstruction patterns such as tongue base retraction, epiglottis anterior-posterior decent, omega-shaped epiglottis,and bilateral arytenoids anterior drawing will also be recorded. The correlation of the upper airway collapsibility between sedative depth and sleep stages (ex. NREM vs. REM) will be evaluated. Besides, mandible advancement will be done under deep sedation. The response will guide further treatment choice for those CPAP non-adherent patient.