The next morning, after his condition had worsened considerably and I had spoken with the consulting pulmonologist and nephrologist, I requested a DNR order which the floor nurses honored just that evening. Thus Dad was saved -- actually, he saved himself -- from not only what he had explicitly rejected but also an exceedingly difficult 2014 that would have confronted him with multiple grave medical problems even if heroic intervention would have succeeded in the short run. He knew what problems he faced, but I didn't know the full extent of them until I read his recent medical records in his apartment the next morning.
Intellectually, I can make sense of all this. Emotionally, I'm still working through it but I take comfort from the fact that he didn't die the death that he didn't want. I'm not saying that he died exactly as he wanted to, given the near-impossibility of communicating verbally on his last day because of the BIPAP. But the fact is, he never said in advance how he wanted to die. Perhaps he didn't know or simply chose to keep that to himself.
The thought "what if?" did cross my mind in 2006 when I was diagnosed with aggressive prostate cancer. Like most doctors, I would not have wanted a prolonged battle against a terminal illness if early intervention had failed. (I am not keen on the word battle in that context.) But again, this doesn't answer the question, How do I want to die? I don't know. Do you?