FSI Analysis of a Human Trachea Before and After Prosthesis Implantation

Abstract

In this work we analyzed the response of a stenotic trachea after a stent implantation. An endotracheal stent is the common treatment for tracheal diseases such as stenosis, chronic cough, or dispnoea episodes. Medical treatment and surgical techniques are still challenging due to the difficulties in overcoming potential complications after prosthesis implantation. A finite element model of a diseased and stented trachea was developed starting from a patient specific computerized tomography (CT) scan. The tracheal wall was modeled as a fiber reinforced hyperelastic material in which we modeled the anisotropy due to the orientation of the collagen fibers. Deformations of the tracheal cartilage rings and of the muscular membrane, as well as the maximum principal stresses, are analyzed using a fluid solid interaction (FSI) approach. For this reason, as boundary conditions, impedance-based pressure waveforms were computed modeling the nonreconstructed vessels as a binary fractal network. The results showed that the presence of the stent prevents tracheal muscle deflections and indicated a local recirculatory flow on the stent top surface which may play a role in the process of mucous accumulation. The present work gives new insight into clinical procedures, predicting their mechanical consequences. This tool could be used in the future as preoperative planning software to help the thoracic surgeons in deciding the optimal prosthesis type as well as its size and positioning.

On Studying the Interaction Between Different Stent Models and Rabbit Tracheal Tissue: Numerical, Endoscopic and Histological Comparison

“…The length of these extrusions was taken as 5 times the diameter of the trachea as performed in previous studies. 29,32 This yields to a length of 27.5 mm for each inlet and for each outlet extension.…”

Computational fluid-dynamics optimization of a human tracheal endoprosthesis

“…The proposed variations allow a smoothed transition of the original top stent surface which due to its 90°-angled geometry causes local flow recirculation. This local flow may be associated to long-term mucous deposition which might cause the prosthesis obstruction, as reported in other studies [4,21,24]. Despite in the past years advances in tracheal endoprosthesis produced a high success rate in the treatment of stenosis [33], and even each new stent has tried to address the weaknesses of its precursors, the perfect stent has not yet been achieved [4,34,33].…”

“…Material parameters E(kPa) ν Silicone 10 3 0.28 studies [18,21,24], after prosthesis implantation, even if the patient gains pulmonary capacity, muscular displacements reduce due to the increase of stiffness of the inserted stent. The proposed stent designs guarantee the same picture in term of stresses, strains and displacements which means that at least from the solid mechanics point of view these work as the original design.…”

“…For these reasons, additional research has to be conducted. In previous studies [18,21,24] we showed that the implantation of a prosthesis, which in case of strong stenosis or tracheal collapse is the only suitable solution, almost totally inhibits the contractile capacity of the muscle, maintaining the tracheal wall section as circular. This muscle inhibition provokes a loss of coughing efficiency, since the contraction of the smooth muscle is especially relevant during coughing, as documented in a previous study [18].…”

“…In particular, in previous studies [23][24][25], we presented numerical analyses of the tracheal stenting technique proposing possible preoperative planning software designed to support thoracic surgical decisions. Recently we also analyze the tracheal behavior under implantations of different stent type (Dumon© and Ultraflex© stent) [21] with the aim of studying the impact of different prostheses on the smooth muscle and evaluate the risk of stent migration.…”