A kinematic study of the oropharyngeal swallowing of a liquid.

Swallowing can become a problem for people with advanced age or laryngeal cancer, especially after surgical resection. The purpose of this study was to quantify the mechanical transport of the bolus through the throat by simultaneously comparing the instantaneous position and velocity of the bolus to the generation of pressure at different sites in the oropharyngeal cavity. Swallows of barium liquid were analyzed using Manofluorography, which simultaneously recorded pressure and barium position through a split screen display. Frame-by-frame analysis was used to describe bolus motion. The graph of head and tail movement showed an hourglass shape with an initial slow, then rapid movement of the bolus head. The peak bolus head velocity averaged 47 cm/s and the maximum acceleration was 460 cm/s2. Comparison of pressure traces with the kinematic curves revealed the relative timings of tongue movement, negative suction pressure from the pharyngoesophageal segment and the contraction wave. The magnitude of the gravity and resistance forces were estimated and relative strengths compared. The pharynx can be viewed as a dynamic conduit with changing diameters. The tongue driving force initially drove the bolus. Laryngeal elevation and the pharyngoesophageal segment developed a prebolus negative suction pressure ahead of the bolus. For vertical swallowing of the barium liquid, gravity played the dominant role in head transport. Contraction of the pharyngeal walls served to clear the tail of the bolus from the pharynx. These results aid in the understanding of the physiology of normal swallowing and provide quantitative data for the evaluation of oropharyngeal reconstruction.