Mine is very simple; I don't want people struggling to keep me alive, if the chances are that I'm going to die soon anyway. But this kind of thing can only work

Mine is very simple; I don't want people struggling to keep me alive, if the chances are that I'm going to die soon anyway. But this kind of thing can only work if the medical staff are trustworthy, and use common sense. My GP knows my attitudes, but in an emergency it might be any old jobsworth that has to interpret my wishes.