Esophageal transport is a bio-physical process that transfers an ingested food bolus from the pharynx to the stomach through the esophageal tube. This process is also referred to as esophageal peristalsis clinically. The process involves complicated interactions among the esophageal wall, neurally controlled muscle activation and the food bolus. Abnormalities of esophageal transport could occur from neural motor disorders or tissue dysfunctions, and lead to esophageal diseases, such as dysphagia (i.e. difficulty in swallowing) or even esophageal cancers. Extracting the underlying physiology and pathophysiology is important. Due to the complexity, however, there is no previous fully-coupled model that is able to resolve the underlying interactions. In our group, we develop and validate two fully-resolved computational models on esophageal transport based on the immersed boundary (IB) method. The first model is developed using the fiber-based IB method, referred to here as the IB-fiber esophageal transport model. The second model is developed using the immersed-boundary-finite-element (IB-FE) method, referred to as the IB-FE esophageal transport model. To our knowledge, these two models are among the first of their kind that integrate the bolus, esophageal wall, and neurally controlled muscle activation into a single simulation.

Following esophageal transport is the process of esophageal emptying, in which the bolus is emptied to the stomach from the esophageal tube. The process of esophageal emptying involves interactions among the esophageal wall, the gastric wall, neurally controlled muscle activation, and the bolus. To resolve those interactions, we develop a fully-coupled bolus-esophageal-gastric model. To our knowledge, this is first fully-resolved esophageal emptying model. In particular, we introduce a simple model to include the passive and active function of the lower esophageal sphincter (LES). We study the influence of non-relaxed LES on the emptying and influence of LES stiffness and gastric wall stiffness on the bulge formation.