Mechanical Properties of Different Airway Stents

Abstract

Central airway obstruction is frequently increases the morbidity and mortality rates of patients suffering from airway obstruction. Insertion of airway stents improves pulmonary function and the quality of life of these patients. The present study was conducted to examine the effect of the radial forces exerted by four main types of airway stents (silicon stent, balloon dilated metal stent, self- expanding metal stent and covered self expanding metal stent) on the trachea and to compare between their mechanical function. Mechanical measurements were done using experiment system that consists of force gauge and self-made adaptors. Numerical simulations were performed on 8 different stents geometries that were inserted into a 3D trachea model. The results of the simulations clearly showed correlation between the diameter of the stent and the stresses. Stents composed of Cobalt alloy and Stainless steel 316L exerted the highest stress value while stents composed of silicon exerted the lowest value. Covering metal stents with less stiff material as silicon or polyethylene reduce significantly the value of stresses. Stenosis (symmetric or non-symmetric) increases significant the level of stresses in all stents. In conclusion, the low stresses found in the silicon stents may be due to weak contact between the stent and the trachea and can explain its migration. Thus, silicon stents are recommended for use in case of short time therapy. Metal stents covered with silicon or polyethylene reduce the stresses on the trachea while still retain strong contact with it. Therefore, they may reduce formation necrosis of mucosa and fistulas while still prevent stent migration.