The way we (meaning my family) look at it is from the standpoint of "are we preserving life or prolonging death?"
I recently shared a story about my grandpa and how we decided to not have his heart restarted if it failed again. It did, we didn't, and he passed away rather peacefully minutes later.
But a little backstory might shed some light on this situation. My grandpa had a serious heart condition and diabetes - a fairly lethal combination. In his lifetime of 80-some odd years, his heart had been restarted for him over 22 times. The first was when he was 32. He lived with chronic pain from his heart issues and his diabetes was most savage. When he was in his late 60s, he had a massive stroke that made it so that he couldn't talk. He had to relearn how to walk. I finally beat him at a game of golf. When my grandma passed, he was alone for awhile and didn't manage his diet and he had another stroke, followed two days later by another heart attack. He had to have been in the hospital for, I dunno, three to four months, not counting rehab. At one point in time, after they had reshocked his heart, they asked him "should we continue this when it happens again?" I thought he was gonna take out the doctor. He grunted quite a bit and pointed at the defrib-thingy-a-bob and pointed to his heart. Yep, keep it coming.
Back to more present times, Grandpa told my dad the last time he went into the hospital that he was ready to die...but not quite. He asked that all his grandkids and his one great grandkid (my son) come visit him so that he could say goodbye to us. That was, by far, one of the hardest things I have ever done. Makes me tear up thinking about it. And we all did. Within a day of that happening, he deteriorated quickly. We had him shocked twice and that was it. No more. But he got to say goodbye to his family and the last memory I have of my grandpa was the big grin he got on his face when he saw his great-grandson. he pointed at my son, and then pointed at me and then back at my son. It was him telling my son to take care of me.
These people who talk about dying with dignity being getting shot up with drugs or taken off feeding tubes...I contend that they know nothing about dying with dignity. For Christians, there is no dignity in death, because we die that physical death because of sin. But even still...I'd say that my grandpa's death comes as close to a dignified death as one could.
So you see, we looked at it from the perspective of were we clinging to grandpa and not allowing his body to do what it needed to do to shut down? or were we taking the measures to save his life. For us, it was medically clear that he was dying and that continuing to shock his heart was only prolonging that.
Whew. Sorry about the long post!!