this is exactly what hospice is about. it is backdoor euthanasia. OTOH, i believe a terminal patient should have the means available to them if they can take no more. the reason i say thins is not because i believe in ending ones own life, its because i think the measures taken to save peoples lives create an unnatural ability to resist death when the moment has come. heart stints and pacemakers are a form of this. it is no more right to force a person to live than it is to force them to die. it has to be a personal choice all the way to the end. and if they are not in control, for any reason, then err on the side of keeping them alive.
another caution - a DNR is an opportunity for hospital workers to create a situation which calls for heroic measures and then evoke the DNR. a DNR is a potential, maybe probable, death sentence.