We studied the effects of swallowing position and viscosity of swallowed bolus on oral and pharyngeal phases of normal swallowing. Video fluoroscopic and scintigraphic examination was done in 25 health volunteers with the head held in neutral posture, neck flexion and rotation. Each subjects swallowed 5ml of thin liquid and thick liquid, and solid.

With chin-down posture, pharyngeal delay time was significantly shortened, and pharyngeal response time and duration of laryngeal elevation was significantly increased. With head rotation, duration of cricopharyngeal opening was decreased, and the bolus lateralized away from the direction of rotation in most of cases. In swallowing of solid bolus, duration of cricopharyngeal opening and duration of laryngeal closure were significantly decreased compared with thick and thin liquid. Pharyngeal residue was greater with thick liquid than with thin liquid. The sequence of events of normal swallowing were also checked.

We conclude that the chin-down posture improve oropharyngeal swallowing mechanism, and the rotational posture helps bolus lateralization to the contralateral side in the pharynx. And the viscosity of bolus preparation has an influence on bolus transit time through the mouth and pharynx.