Swallowing and breathing patterns during sleep in patients with obstructive sleep apnea

The aims of this study were to determine the frequencies of swallowing and swallowing associated with arousals during sleep in patients with obstructive sleep apnea (OSA) and to determine whether these were associated with the severity of OSA and differed according to the preceding breathing route.

Standard audio-video polysomnography including an evaluation of swallowing-related elevation of the thyroid cartilage and breathing route (i.e., nasal or oronasal) was undertaken in an academic sleep laboratory. Fifty-six patients were analyzed (13 non-OSA patients, 17 mild, 10 moderate, and 16 severe OSA).

The frequency of swallowing per hour of sleep was significantly higher in the severe OSA patients when compared to mild OSA patients (mild OSA, 3.1/h and severe OSA, 8.4/h). This was mainly due to the significantly higher frequency of swallowing associated with a respiratory event-related arousal in the severe OSA patients when compared to non- and mild OSA patients (non-OSA, 0.6/h; mild OSA, 1.0/h; severe OSA, 6.0/h), especially when swallowing was preceded by oronasal breathing (non-OSA, 0.2/h; mild OSA, 0.4/h; severe OSA, 4.2/h).

Swallowing frequency during sleep can increase with increasing OSA severity in most OSA patients. These events are predominately associated with respiratory event-related arousals and are more frequent when preceded by oronasal breathing. The observed swallowing under high ventilatory needs may compromise the maintenance of the pharynx as a conduit for airflow in OSA patients.