Does a Rebreather hose begin to collapse under pressure?

I was reading an article of rebreather divers going to something like 500'
and began wondering why the flexible hose and the compressable air in the
flexible hose doesn't collapse under the pressure. Perhaps it does, but it does
not seem apparent. Would anyone care to explain this to me? What does -or-
doesn't happen happen and why in relationship to pressure and the hose.

Thanx,

Its all at ambient pressure. They do collapse under negative pressure.

Matt