I just meant that you should let them die, when they don't want to live anymore.
The OP didn't mention anything about them not wanting to live anymore. You might want to amend your post to mention that before taking any action (or lack thereof) you might ask them if they would prefer to be saved or just left to die, and agree to be bound by their preference.
If they were unable to express their preference (for whatever reason, for example because you're only able to watch them from a monitor and save them remotely), what unilateral action would you take for an elderly person?