On a somewhat related note
I have never experienced the phenomenon, but I have slept at altitude and the low oxygen effects can be disturbing, to put it mildly...
The effects of sleeping in such conditions range from the simply annoying (Every time you start to drift off you 'hear' a phone ringing, or a knock on the door) to the VERY disturbing (Technicolor Nightmares that make the most horriffic scenes from horror movies look like Disney movies for toddlers)
Finally, Sleep paralysis is normal... the body supresses motor function during sleep to prevent self injury during dreams... It is abnormal when this suppression is not there (sleep walking), and when this suppression remains after waking up....