Session: 10.5 - Non-Newtonian fluid flows

Paper Number: 158585

158585 - Hydrodynamics of Thin and Mildly Thick Food Boluses in the Oropharynx During Pharyngeal Constriction and Epiglottis Motion 

Abstract: 

Understanding the mechanisms underlying swallowing disorders is crucial for developing effective, etiology-driven interventions for patients with dysphagia. However, current clinical approaches to dysphagia remain largely symptom-focused, as the complex relationships between symptoms and their causes are not yet fully understood. This research sought to investigate the factors contributing to liquid entering the laryngeal vestibule, leading to aspiration symptoms. To achieve this, anatomically accurate, transparent throat models with a movable epiglottis were utilized to simulate the swallowing process. Pharyngeal contraction was replicated using two clippers, while the motion of the pharyngeal wall was monitored with multiple gyroscopes. Liquid movement was visualized using fluorescent dye, with observations captured from various perspectives, including side, rear, front, and internal views, to identify key hydrodynamic factors driving aspiration.

Three variables were considered in this study: fluid consistency, the site of fluid introduction, and the speed of fluid delivery, assessing their roles in aspiration risk. It identified three primary pathways through which liquids enter the airway: via the interarytenoid notch, the cuneiform tubercle recesses, and beneath the epiglottis. Among the variables, fluid viscosity had the most significant influence on aspiration risk. Water was found to pose a considerably higher risk compared to slightly thicker fluids, such as a 1% methylcellulose solution. Additionally, the location of fluid introduction played a critical role; liquids introduced at the front of the mouth were more likely to cause aspiration than those introduced at the back. Dispensing speed showed variable effects depending on the introduction site: slower speeds increased aspiration risk for anteriorly introduced liquids due to enhanced off-edge capillary flows, whereas slower speeds significantly reduced aspiration for posteriorly introduced liquids by minimizing notch overflows. Observing swallowing hydrodynamics from multiple angles enabled detailed, site-specific analysis of aspiration mechanisms. This approach provides valuable insights for understanding the etiology of dysphagia and can inform the development of targeted interventions to mitigate aspiration risks.

Presenting Author: Amr Seifelnasr University of Massachusetts, Lowell

Presenting Author Biography: Amr Seifelnasr, a PhD student in Biomedical Engineering, holds a Bachelor's in Mechanical Engineering with 22 years of industry experience. His research focuses on respiratory dynamics, inhalation, and intranasal drug delivery systems, combining computational simulations with in vitro experiments. He also studies human deglutition, investigating the biomechanics of swallowing and the mechanisms behind swallowing disorders.