CPR only keeps the blood flowing until the medics get the heart started again. It can lead to brain damage. I would hate to end up a drooling idiot. Worse would be a fully functioning brain but total physical immobility.
After my stroke I was bedridden, I had a catheter to drain my piss, wore a nappy and was cleaned up by the nurses. My motor functions were very limited and I had to be fed by a carer as I couldn't use a knife and fork. But it was bearable as I knew time and therapy would restore my faculties. However, if that was permanent, I would prefer to end it all.
Where does DNR end and assisted suicide begin?