My father-in-law did not want his life prolonged by extraordinary means.
When he suffered his final stroke, my sister-in-law requested that the hospital staff NC ("No Code")
The next day she came back, she found her father drugged into unconsciousness whereas the day before he had been partially lucid. In other words, he was being prepped to die!
Immediately she revoked the "No Code" and my father-in-law received treatment and feeding again.
This happened in Pennsylvania.
DNR, "Do not resuscitate" often becomes "Do not treat"
That's one reason why we want my father here at home. As explicit as you can be about what kind of care you want for your loved one, you never know unless you're right there keeping your eye on things.
The National Right to Life Committee has put out an excellent model document called the "Will to Live." My mother-in-law used it as a basis for her own advance directives, PLUS (this is important) she had a serious talk with all her children discussing and explaining exactly what she would want under different circumstances.
http://www.nrlc.org/euthanasia/willtolive/
Go there, do that.