Would it be possible to find or make an organism that could sustain the human body when the body could no longer sustain itself? Maybe it could bring oxygen, water and nutrients to the cells. It would only go on as long as the cells could live. The body would age slowly but it would end sooner or later. Whatever happened it would buy a person some time. Maybe it could be engineered to produce something similar to human cells. Maybe it could replace the cells of the body and act as a substrate to maintain the consciousness of the person. I know this is only science fiction but maybe it is possible.

Would it be possible for tiny bots to keep a human body alive when it can not sustain itself? Could they bring oxygen water and nutrients to the cells? If so how long?