This is the location to find information about a living will - which after the Schiavo case you may really want to consider having. An advance directive aimed at ensuring that your doctors and significant others know what treatments you would, or would not, want has suddenly become the most important tool one could have in the event that there is any difference between your views and your family's views about end of life care. Country simple: if you would want a feeding tube removed were you in persistent vegetative state, and you think that it is enough that you told your family as much, think again and get a living will. Your state's information is above.
Warning: not guaranteed to protect you against the combined legislative force of a majority of congress.