Vol. 284, Issue 6, G933-G939, June 2003
Relative contribution of various airway protective mechanisms
to prevention of aspiration during swallowing
Bidyut K.
Medda1,
Mark
Kern1,
Junlong
Ren1,
Pengyan
Xie2,
Seckin O.
Ulualp1,
Ivan M.
Lang1, and
Reza
Shaker1
1 Medical College of Wisconsin Dysphagia Institute,
Division of Gastroenterology and Hepatology, and Departments of
Medicine, Radiology, and Otolaryngology, and Human Communication,
The Medical College of Wisconsin, Milwaukee, Wisconsin; and
2 Department of Gastroenterology, Peking University
First Hospital, Beijing 100034, China
Deglutitive airway protective
mechanisms include glottal closure, epiglottal descent, and
anterosuperior displacement of the larynx. Aspiration of swallowed
material may occur during the pre-, intra-, or postpharyngeal phase of
swallowing. Our objectives were to determine the relative contribution
of the airway protective mechanisms during each phase of swallow in 14 decerebrated cats before and after suprahyoid myotomy, epiglottectomy,
and unilateral cordectomy. After myotomy, superior excursions of the
hyoid, thyroid, and cricoid cartilages and anteroposterior diameter of
maximum upper esophageal spincter (UES) opening were significantly
diminished, but the incidence of pharyngeal residue significantly
increased (P < 0.05). No aspiration was observed in
the predeglutitive period. After myotomy, the incidence of aspiration
significantly increased in both intra- and postdeglutitive periods.
Epiglottectomy did not alter aspiration incidence, but unilateral
cordectomy resulted in a 100% incidence of intra- and postdeglutitive
aspiration. In conclusion, glottal closure constitutes the primary
mechanism for prevention of intra- and postdeglutitive aspiration, but
laryngeal elevation may assist this function. Bolus pulsion without
laryngeal distraction can open the UES, but at risk of aspiration due
to decreased pharyngeal clearance. The epiglottis provides no apparent airway protection during any phase of swallowing.
suprahyoid muscles; vocal cord; epiglottis, larynx