The purpose of this study is to evaluate the upper airway collapsibility by sleep endoscopy in different sedative levels. Propofol pump infusion will be used to achieve conscious sedation. Bispectral Index monitor will be applied to the monitor the conscious level. Two different sedative levels (BIS 65-75, 50-60) will be achieved for upper airway evaluation. The severities of upper airway obstruction will be evaluated the correlation to the disease severities. Mandible advancement will be done to evaluate the response for oral appliance.