Mouth breathing is associated with increased airway resistance, pharyngeal collapsibility, and obstructive sleep apnea (OSA) severity. It is commonly believed that closing the mouth can mitigate the negative effects of mouth breathing during sleep. However, the investigators propose that mouth breathing serves as an essential route bypassing obstruction along the nasal route (e.g., velopharynx). The present study investigates the role of mouth breathing as an essential route in some OSA patients and its association with upper airway anatomical factors.

Participants underwent drug-induced sleep endoscopy (DISE) with simultaneous pneumotach airflow measurements through the nose and mouth separately. During the DISE procedure, alternating mouth closure (every other breath) cycles were performed during flow-limited breathing.

The investigators evaluated the overall effect mouth closure on inspiratory airflow, and the change in inspiratory airflow with mouth closure across three mouth-breathing quantiles. The investigators also evaluated if velopharyngeal obstruction was associated with mouth breathing and a negative airflow response to mouth closure.

Inclusion Criteria:

• Diagnosed obstructive sleep apnea (AHI > 5 events/h).
• Scheduled to undergo clinical drug-induced sleep endoscopy.

Exclusion Criteria:

• pregnancy
• age under 18 years
• poor general health
• allergy to propofol or dexmedetomidine
• history of surgical treatment for sleep apnea, such as palate, tongue base, or epiglottis surgery.

We do not plan to make the IPD available to other researchers.