That's the thing, it raises a lot of philosophical questions. How do we define "death" if we can maintain the unity and function of the organism by supplanting its systems? What is the appropriate use of this technology?

There's a fascinating (though sad) case of a boy who became brain dead after contracting viral meningitis. I remember reading about it in a bioethics class. He lived for another 20 years without anything resembling a brain. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5102206/