I have a friend who had a spontaneous pneumothorax. He even wrote a song about it after he recovered.

I myself punctured and collapsed both lungs. My thinking is: if there's a reasonable chance I'll survive, go for it. If there's not, stop trying to prolong the inevitable. That said, when I had the accident they told my wife to get there as fast as she could because I was likely not going to make it, and that was thirty years ago. So: if they're confident I'm going to die, don't try to prolong it :-)