The Effect of Mouth Closure on Airflow in OSA

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