My daughter is in her final year of nursing school at UCLA. She is in her 300hr rotation at a local LA-area hospital ICU this quarter. She recently was involved in a code blue of a very sick 80+ yr-old woman who had DNR on file. The woman's daughter was in the room and went into such hysterics that the hospital decided to ignore the DNR. My daughter performed chest compressions in an attempt to revive the woman, but was ultimately unsuccessful. The daughter was satisfied that the hospital did their best to help her mother. Te mother didn't complain despite having her DNR ignored.
On the other hand, my stepfather's cousin, in her mid-90's, had her DNR ignored when she went into cardiac arrest at an assisted living facility in southern California. She was furious when she became conscious and aware of what was done to her a few days later. She wanted to end her suffering and was ready to go. She lived another year or so after that, but was quite unhappy the entire time.
Knowing what to do at the (possible) end of life is not easy. I had had very clear instructions from my father about what to do if he was left alive and dependent on machines to keep him alive. A few years later he went into liver and kidney failure and was being kept alive in the ICU on a ventilator while I flew back from a business trip in the Philippines. While my brother and sister helped make the decision, I, as the person named in the durable power of attorney, had to make the final call. You can imagine what it feels like to tell the doctor to unplug the machines and then watch your father fade away and die over the next couple of days. It was a devastating thing for me, personally, to have to say. With or without instructions, end-of-life decisions are hard!