Mathematical modeling of the pharyngeal phase of swallowing

Thesis (Ph. D.)--University of Washington, 1996A significant portion of the population suffers from difficulty in swallowing, known as dysphagia, including 12 to 13% of hospitalized patients and 40% of nursing home residents. Dysphagia can make it impossible for a person to eat and drink normally which can lead to malnutrition, cachexia, and dehydration. During the pharyngeal phase of swallowing, the food or liquid to be swallowed, known as the bolus, passes the entrance to the larynx. If the bolus penetrates into the larynx, aspiration or choking can occur. Chronic aspiration can lead to serious lung infections such as pneumonia. Approximately 8,000 people in the United States choke to death each year.In this research, a mathematical model that simulates swallowing was developed to analyze the parameters affecting the transport of the bolus through the pharynx. This work is a first attempt at modeling the pharyngeal phase of swallowing. The pharyngeal phase of swallowing is a complex, 3-dimensional, moving-boundary problem involving both fluid and solid motion. The model developed is a 2-dimensional representation of the fluid dynamics as the bolus passes through the pharynx. The mechanics of the pharyngeal muscle was not modeled, but was accounted for by prescribing the motion of the boundaries of the bolus in contact with the pharyngeal musculature. This boundary motion was found through image analysis of individual videofluoroscopy studies. The model was solved with a commercial computational fluid dynamics program, FIDAP.The model was applied to analyze data from a normal subject to investigate the effect of bolus volume, bolus viscosity, head positioning, and gravitational forces on the pharyngeal swallow. It was found that the viscosity had the greatest effect on the transport of the bolus through the pharynx. The most significant effect of modifying bolus volume or head positioning was to change the geometry of the bolus as it passed through the pharynx. Gravitational forces were found insignificant in the transport of the bolus except in the case of low-viscosity fluids.The effect of these parameters on swallowing disorders was also investigated by modifying the model and applying the same modeling techniques to data from a dysphagic subject. These studies provided insight into how laryngeal penetration can be reduced by modifying bolus properties