Are airway stents permanent?

The permanence of airway stents depends on the type of stent used:

- Metal stents (e.g. nitinol, stainless steel) are considered permanent implants. They are not typically removed unless there are complications. The stents stay in the airway for the remainder of the patient's life.

- Silicone stents need to be periodically replaced every 3-6 months as the silicone can deteriorate over time. So silicone stents are considered temporary.

- Biodegradable stents dissolve over time and don't require removal. Polydioxanone and copolymers are used. Their duration can be tuned.

- Hybrid stents may last 1-2 years before needing replacement. So semi-permanent. 

- In benign conditions that resolve, like post-tracheal injury, stents may be removed after 6-12 months once the airway is stabilized.

So in summary:

- Metal = permanent

- Silicone = temporary

- Biodegradable = dissolve over time

- Hybrid = semi-permanent The intended duration guides stent selection. 

For lifelong conditions like tracheomalacia, permanent stents are chosen. For short-term relief like in malignancy, temporary options are preferred.