I went through the same a few years ago with hospice. She had emphysema and real trouble breathing. She was mentally checked out after a few days in the hospital and opted for hospice. They started morphine and for a couple of hours she was able to breathe and felt great. She even said maybe she could get out of there - she fully expected to die.
Well after that she passed out, didn't wake up again, and died. Bothers me greatly to this day and I wish I had been there for the whole thing to challenge some of the decisions made that my parents didn't contest.