So, I've been kicking around a sort-of "return from another world" idea for a bit now. Basically, the MC gets the crap kicked out of him and ends up in a deep coma with very little brain activity.* On a cosmic scale, he is considered dead and his soul is taken to Hell because, unbeknownst to him, he is half demon. Over the course of five Earth years (20-25 in Hell), he helps lead a revolution that results in humans taking over Hell. He then discovers that his body back on Earth is still alive as his mother refused to allow the doctors to pull the plug despite all the indicators that he will not recover. He and his allies devise a way to send him back to his body so he can resume his old life.**
All that is to say: there's reasons behind his waking from such a long coma/brain death situation even though it wouldn't happen in real life. My question just surrounds what the recovery period would look like.
Obviously his muscles would have atrophied, but how long would it take to build them back to normal after such a long period of inactivity? How bad would the atrophy be? Would he be able to move at all after first waking up? Would he be able to speak, or make any sort of vocalization, like a grunt or moan or something? Would he even be able to open his eyes?
How would it affect him from a cognitive perspective? Would his brain be pretty much the same as it was when he went to into the coma, or would there be massive amounts of damage or cell death? Would I need to explain it away as his brain restructuring itself to align with his current consciousness in order for it to be believable that he'd be able to function?
Lastly, what kind of monitors would that have set up around the time of his awakening, and how would they be affected by it? I would expect the heartbeat monitor would change in some way since there is difference between conscious and unconscious heart-rate (I think). Would they have something monitoring his brain activity that would alert them to the fact that consciousness had returned to the brain, or is that kind of monitoring only possible through specialized equipment like MRIs that you wouldn't have running all the time? What else would they be monitoring in a coma patient, and how would his sudden awakening affect them? Would they be sounding alerts and alarms of some sort like you often see in TV shows and movies?
I know that's a lot of questions, so I don't anyone to feel like they have to answer every single one themselves. Any insight you could offer me on any of them would be helpful. Also, if there are other things you think I should I know in order to write about this more accurately, feel free to mention those as well. Thanks in advance to all who answer!
*Basically just autonomic functions. No signs of consciousness or even dreams.
**This is the very short version, of course. There's a lot more to it in regards to the "hows" and "whys" of all this, but they're mostly irrelevant to the question at hand. Also, the miraculous nature of his recovery will factor into the plot, so no need to focus on that aspect of it.