The exam for brain death is simple. A doctor splashes ice water in your ears (to look for shivering in the eyes), pokes your eyes with a cotton swab and checks for any gag reflex, among other rudimentary tests. It takes less time than a standard eye exam. Finally, in what's called the apnea test, the ventilator is disconnected to see if you can breathe unassisted. If not, you are brain dead. (Some or all of the above tests are repeated hours later for confirmation.)
Here's the weird part. If you fail the apnea test, your respirator is reconnected. You will begin to breathe again, your heart pumping blood, keeping the organs fresh. Doctors like to say that, at this point, the "person" has departed the body. You will now be called a BHC, or beating-heart cadaver.
What if there is sound evidence that you are alive after being declared brain dead? In a 1999 article in the peer-reviewed journal Anesthesiology, Gail A. Van Norman, a professor of anesthesiology at the University of Washington, reported a case in which a 30-year-old patient with severe head trauma began breathing spontaneously after being declared brain dead. The physicians said that, because there was no chance of recovery, he could still be considered dead. The harvest proceeded over the objections of the anesthesiologist, who saw the donor move, and then react to the scalpel with hypertension.