Experimental and Computational Analysis of Bolus Fragmentation during Model Oropharyngeal Swallowing

Fragmentation of the liquid bolus during swallowing may enhance the risk of airway exposure to the passing bolus and thereby increase vulnerability for aspiration. Our goal was to develop an experimental and a computational model that depicts how physical forces applied to a model bolus affect cohesion during simulated swallowing. A physical replica of the oral cavity was created through 3D printing to emulate the bolus-accommodating tongue within the oral cavity. The intent was to assess the effect of linear force applied to the bolus, similar to that of the deforming tongue during bolus propulsion through the acceleration and rapid deceleration of a pulley system, and to assess the ensuing degree of bolus fragmentation. Upon enaction of linear force applied to the contained bolus, a portion of the bolus characteristically fragmented and exited the device with measurable displacement velocity. Experimental and computational results demonstrated that the degree of bolus fragmentation increased as a function of bolus volume and velocity and decreased as a function of viscosity. We deduce that these physical attributes of the fluid bolus, when combined with the timing of laryngeal closure, pharyngeal peristalsis, and inspiratory air flow, contribute to an multi-component model of aspiration vulnerability during swallowing.