Protocol used for sedation and acquisition of upper airway collapsibility data during dexmedetomidine or propofol sedation. Sedation was assessed with the modified five-point composite Observer’s Assessment of Alertness/Sedation (OAA/S) scale and the Richmond Agitation–Sedation Scale (RASS). The sedation scale scores were as follows: (1) OAA/S scores 1: deep sedation, 2 to 4: light to moderate sedation, and 5: alert state; and (2) RASS score 0: alert and calm, −1: sustained awakening more than 10 s to voice, −2: briefly awakens to voice less than 10 s, −3: movement to voice but no eye contact, −4: movement to physical stimulation, and −5: unarousable. Pcrit, pharyngeal critical pressure.