My mother had a massive cerebral hemorrhage and lapsed into a deep coma almost immediately. During the next three days we watched as her organs shut down, her skin became mottled, her urine got a deeper and deeper yellow and diminished to a trickle, and her breathing became more and more shallow and, at the very end, labored.
My sister and I took turns, and we essentially sat there and watched her breathe. Hospice and her doctor kept her very comfortable and also obeyed her DNA mandate, which she had put in place several years ago.
The pacemaker with a relatively new battery probably kept things going on longer than was necessary, but she had oxygen, morphine and ambien and so was relatively comfortable. Once she had the stroke, there was no one at home but the shell, which did soldier on for 72 hours.
Then it all just stopped.