What material is used for tracheal stents?

The most common material used for tracheal stents is:

- Nitinol (nickel-titanium alloy) - This is the most widely used material for tracheal stents. Nitinol is flexible and has "shape memory", allowing it to be compressed for delivery and then expand once deployed in the trachea. Nitinol stents can be self-expanding.

- Stainless steel - Stainless steel has good radial strength to hold the trachea open but is less flexible than nitinol. Stainless steel stents require a balloon to expand them.

- Silicone - Silicone is highly biocompatible and conforms well to the airway anatomy. It is less likely to migrate but provides less outward force than metal stents.

- Hybrid stents - These combine metal (nitinol or stainless steel) with silicone to get the benefits of both. The metal provides structural support while silicone minimizes tissue reaction. 

- Bioabsorbable polymers - These stents dissolve over time and include materials like polydioxanone. This avoids a second procedure to remove the stent. 

The optimal material depends on factors like the type of obstruction, location in the trachea, and expected longevity of the stent. Nitinol is preferred for most malignant obstructions. Silicone or bioabsorbable stents may work better for benign stenosis. The patient's anatomy also helps determine the best stent material.