I dove hundreds of times for Cousteau, back in the day. Deep dives. Deepest 230 feet. On regular air. Anyway, no nose bleeds then...BUT...for years afterward I got them. I'd be sitting at dinner or anywhere and suddenly my nose would bleed. It eventually went away but after a number of years away from diving, when I got back in, sure enough, my nose bled - while diving this time. I can not offer any medical advice or other but that's my story related to nose bleeds.