This discussion is intellectually interesting, but in order to exit the rabbit hole of research of which disinfection method would be better/safer, I just bought a set of 100 cannulas for below 40,- EUR (including shipping), and I think I will just throw them away regularly.
From my professional medical view, there are only two answers to this:
1) if you are very serious about hygiene there is absolutely no other option than discarding the cannula after a single use. It is entirely impossible to clean long tubing in a safe way with any method any of you has access to, so forget about it.
2) if you are relaxed about all this, you can re-use and switch cannula at random. The risk of serious infection is very low unless you have some form of inmunodeficiency and the person you have taken the used cannula from has a currently active infection. Even then, the most likely infections are things like common cold…not exactly threatening.
