Inner tube?

STENT

This medical device keeps a blocked passage open like scaffolding in an artery.

"Inner tube?" plays on the double meaning of the word "tube." In everyday language, an inner tube is the inflatable rubber part of a tire, but in medicine, a "stent" is a small tube inserted into a blood vessel or airway to keep it open. The question mark signals that the clue is a pun, hinting you should think beyond the literal definition. The answer "stent" fits as a clever twist on the idea of an inner tube.