Experimental analysis and biaxial biomechanical behaviour of ex-vivo sheep trachea

Purpose: The purpose of this study is to investigate the mechanical behaviour of the tracheal tissue under biaxial tensile loading. Furthermore, the study examines the material properties of the tissue through a study of the model parameters for six constitutive models. Materials and methods: The fourteen (n = 13) trachea sheep (Vleis Merino) pieces of tissues measured to be ~ 30 x 20 mm where only the effective area subjected to engineering strain was ~ 25 x 16 mm. In this study, we assume that the tracheal tissue is anisotropic and incompressible, therefore we apply and study the material parameters from six models namely the Fung, Choi-Vito, Holzapfel (2000), Holzapfel (2005), Polynomial (Anisotropic) and Four-Fiber Family models. Results: The results show that the trachea tissue is twice as stiff along the circumferential direction as it is along the longitudinal direction. It is also observed that the material properties are different (non-homogeneous) along the trachea. Conclusions: The findings of this study will benefit computational models for the study of tracheal diseases or injuries. Furthermore, these findings will assist in the development of regenerative medicine for different tracheal pathologies and in the bioengineering of replacement tissue in cases of damage.

Tracheal Narrowing and Tracheomalacia

The etiologies of tracheal narrowing and stenosis are myriad. An important first step in formulating an imaging differential diagnosis is to divide tracheal narrowing into the following categories: neoplastic (benign and malignant), idiopathic, traumatic, inflammatory/infiltrative, and that caused by underlying pulmonary disease. Lesion location along the tracheobronchial wall, the presence or absence of calcifications, and evidence of extension through the tracheal wall are important characteristics that may help to further narrow the differential diagnosis. Post-intubation or post-traumatic tracheal stenosis is often treated by serial balloon dilatation, stenting, or segmental resection with re-anastamosis. Evaluation of both the length and degree of stenosis is important. Tracheomalacia is a dynamic process that is best evaluated with inspiratory and forced expiratory CT images to demonstrate tracheal collapse. Like other tracheal diseases, tracheomalacia may mimic asthma, or affected patient may present with non-specific symptoms. Significant respiratory dysfunction may result if tracheomalacia goes untreated. In the adult population, most tracheal tumors are malignant, and squamous cell carcinoma is the most common tumor detected.

FSI Analysis of a Human Trachea Before and After Prosthesis Implantation

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.