Pharyngeal swallowing elicited by fluid infusion: role of volition and vallecular containment.

Nonalimentary swallows minimize aspiration by clearing accumulated fluid from the pharynx. This study aimed to define 1) the pharyngeal sensory field to elicit swallowing and 2) the effect of infusion rate, volition, taste, and temperature on pharyngeal swallows. Test solutions were directed into the valleculae at 6.5, 11.5, and 32 ml/min through a catheter in eight healthy volunteers. Deglutition was signaled with electromyography and electroglottography. Spatial distribution of infusate before swallowing was studied using videofluoroscopy coupled with a video timer. Volitional control was assessed with rapid or restrained swallows. Pharyngeal swallow latency decreased as the instillation rate increased, was potently modified with volition, and was unchanged by infusate taste or temperature. Water infusion into the valleculae did not trigger pharyngeal swallowing until liquids overflowed and reached the aryepiglottic folds or pyriform sinuses. The variation in swallow latency among flow rates was mainly due to the duration of liquid containment within the valleculae. This suggests that the valleculae act to contain pharyngeal secretions and residue and prevent aspiration by diverting their contents around the larynx before swallowing.