Computational fluid-dynamics optimization of a human tracheal endoprosthesis

The Dumon silicone stent is widely used in human medicine for treating tracheal diseases. Although presenting many advantages, as its facility of positioning and removing and its relative low cost, commonly reported complications include stent migration, inflammatory granulation tissue formation, and obstruction. Taking into account this last aspect, in this work we propose an improved stent design which may help in preventing episodes of mucous accumulation. In particular, we changed the design of the stent extremities in order to improve the flow field which cyclically crosses the prosthesis. To evaluate the performances of this new design, a finite element model of a human stented trachea was developed using a fluid-structure interaction approach (FSI). The geometry of the trachea is obtained from computed tomography (CT) images of a healthy patient. The simulations were performed using a finite element-based commercial software code. The tracheal wall is modeled as a fiber reinforced hyperelastic solid material in which we introduced the anisotropy due to the orientation of the fibers. Different new prosthesis designs were tested. Results showed that linear and parabolic transitions of the top and bottom stent extremities reduce the local vorticity field preventing high local flow recirculations during breathing.