Comas are not a form of hibernation because there is no appreciable drop in physiological activity to count as hibernation. There is no evidence that the human species as we know it has ever been able to hibernate. Just the fact that bedsores (pressure ulcers) exists gives evidence that the human form was not evolutionary designed to become capable of hibernation.
However, in the YouTube video link below research anesthesiologist Rob Henning states that someday using a combination of biochemistry and cooling systems humans might be able to have a different kind of hibernation than other kinds of animals. This kind of hibernation would be useful for such applications as preventing bone mass loss in astronauts and better preservation of donor organs.