I have my medical directive filled out in what is called POLST, or Physician Ordered Life Sustaining Treatment. I have specified the conditions that will allow treatment to stop. The notice is a pink piece of paper on my refrigerator.
By law, an ambulance attendant is required to give all life-saving procedures possible. This may not be the preference of the patient. If the situation is at all serious, the attendant will look for this form on the refrigerator. The ambulance attendant will know my medical wishes, save or throw overboard:-)
I also have this notice on the dash of my car, just in case I am in an auto accident.
This is the official form for California.
To learn more about this form for a nationwide application, go to http://polst.org/
For California, go to http://capolst.org/