Modelling the air mass transfer in a healthy and a stented rabbit trachea: CT-images, computer simulations and experimental study

Abstract

Endotracheal stenting is a controversial treatment for tracheal stenosis. Metallic stents have advantages but also show disadvantages such as restenosis due to epithelial hyperplasia and granuloma formation. In this work we analyze the response of a rabbit tracheal wall during normal breathing under implantation of a Zilver® Flex™ Stent. Trachea geometries were reconstructed using medical images for both healthy and stented rabbit. The numerical model was used for analyzing tracheal stresses before and after prosthesis implantation using a fluid–structure interaction approach (FSI). Unstructured tetrahedral-based grids were used to perform the simulations with a finite element-based commercial software code. Experimental tests on rabbit trachea samples were performed in order to get the material property constants. Deformations of the tracheal cartilage rings and of the muscular membrane as well as the maximum principal stresses of the tracheal wall were analyzed and compared with those of the healthy trachea in absence of prosthesis. In addition, an experimental validation of the model was provided. The prosthesis was percutaneously implanted under fluoroscopic control. Period of the study was 90days. The tracheal wall response was assessed by means of computerized tomography by endoscopy, macroscopic findings and histopathological study. Experimentally revealed tissue damages due to the stent were then compared with numerical results. Interesting correlation with maximal principal stresses and induced wall shear stress were found in the same region.