Finite element simulation of food transport through the esophageal body

Abstract

The peristaltic transport of swallowed material in the esophagus is a neuro-muscular function involving the nerve control, bolus-structure interaction, and structure-mechanics relationship of the tissue. In this study, a finite element model (FEM) was developed to simulate food transport through the esophagus. The FEM consists of three components, i.e., tissue, food bolus and peristaltic wave, as well as the interactions between them. The transport process was simulated as three stages, i.e., the filling of fluid, contraction of circular muscle and traveling of peristaltic wave. It was found that the maximal passive intraluminal pressure due to bolus expansion was in the range of 0.8-10 kPa and it increased with bolus volume and fluid viscosity. It was found that the highest normal and shear stresses were at the inner surface of muscle layer. In addition, the peak pressure required for the fluid flow was predicted to be 1-15 kPa at the bolus tail. The diseases of systemic sclerosis or osteogenesis imperfecta, with the remodeled microstructures and mechanical properties, might induce the malfunction of esophageal transport. In conclusion, the current simulation was demonstrated to be able to capture the main characteristics in the intraluminal pressure and bolus geometry as measured experimentally. Therefore, the finite element model established in this study could be used to further explore the mechanism of esophageal transport in various clinical applications.

Figure 1

Geometrical model for the simulation of food transport process.

Figure 2

Procedure used to obtain the true zero-stress state and definition of three states: (A) Bonded no-load state; (B) separated no-load state; and (C) true zero-stress state.

Math 1

Math(A1).

Math 2

Math(A2).

Math 5

Math(A5).

Figure 3

Example of the fluid element and fluid link element.

Figure 4

Bolus shape (A) before the muscle contraction (B) at the end of muscle contraction and (C) when the peristaltic wave reaches the LES.

Figure 5

Bolus shape and intraluminal pressure distribution along the length (A) at the end of bolus filling and off response (before muscle contraction) (B) at the end of muscle contraction at the top 1 cm segment (C) when the peristaltic wave reaches the middle of the entire segment and (D) when the peristaltic wave reaches the end of segment (LES).

Figure 6

Stress distributions along the esophageal wall under the expansion of food bolus.

Figure 7

Mass flow rate at fluid link element 8091 (1 cm away from the top end connecting the fluid cavity 5091 and 5090) during the muscle contraction and wave transport. 1 represents the moment when the rigid body is in contact with the tissue structure (start of contraction); 2 the end of contraction at the top 1 cm segment; 3 when the contraction wave leaves the fluid cavity 5091 (1 s after contraction); 4 when the contraction wave is 1 cm away from cavity 5091 (2 s after contraction).

Figure 8

Intraluminal pressure at cavity 5090 and 5091 during the two seconds of fluid reflux.