I don't know either, but lots of stuff in hospitals is disposable, because this is easier than figuring out a system to disinfect & re-use it. Although perhaps

I don't know either, but lots of stuff in hospitals is disposable, because this is easier than figuring out a system to disinfect & re-use it. Although perhaps that makes more sense in an operating theatre than many of the lower-risk places people now wear them, all day.