Of course it’s possible.
Happens all the time.
KRAMER: I didn’t know it was possible to come out of a coma.
JERRY: I didn’t know it was possible not to know that.
***************
GINA: Then kiss me right in front of him.
JERRY: I cant. What if he wakes up?
GINA: A man is lying here unconscious and youre afraid of him? What kind of a man are you?
JERRY: A man who respects a good coma. If it was one of those in and out comas, maybe. But when a guys got a coma going like this you dont want to mess with it.