After watching an ambulance crew trying to resucitate my Dad after he had a massive heart attack I can fully sympathise with your view. My Sister and I both realized that to all intents our Dad had died and we wanted the resucitation to stop, however, our Step-Mum was hysterical and begged them to keep trying which they did for about anouther 20 minutes - so I guess you just have to "play it by ear" in each individual case so that the people left behind feel that you have done everything possible for their loved one.