You might want to look at a Protective Medical Decisions Document:
http://www.internationaltaskforce.org/pmdd.htm
That reminds me...My Aunt, just a few yrs ago, had her pacemaker go awry. They admitted her to the hospital and put her under a lot of meds. When she didn't know her kids when they came in, her kids decided to speak to the Dr and have her food taken away. They claim she wouldn't have wanted to live on "machines". My dad was furious at the time and said they killed her. He says it was the influence of the drugs that was the reason she was out of it. Yet a Dr. went ahead and stopped giving her food.