"We have to have them because unexpected events can take away the ability to make our wishes known," she said. "But like a map, it's incomplete -- slightly out of date with traffic or construction or a tree fell on the road. This is where personal judgment comes in."
And even asking a blinking patient can be ambiguous. In Rudd's case, learning his wishes depended on the how Menon asked the questions, Charo said.
"I ask, 'Do you want to die?' and you say, 'no." But I haven't asked all the questions, and if you are never going to get better, what would you rather do, keep you like this forever?" said Charo. "For someone just emerging from the horror and depression of this condition might say, 'no,' to everything."
Today Rudd has been moved to a hospital that specializes in rehabilitation for spinal injuries. He can move his head an inch either way and smile or grimace and has regular visits from his children and parents.
"I think he will continue to make progress," Menon said. "We hope some of his cognitive function and facial muscles will come back eventually."
Rudd will forever be on a ventilator and may change his mind about living, months or years down the road, but that's his call.
"This is about the autonomy of an individual," he said. "I would try my best to respect his wishes if he was cognitively intact and not depressed."
Still, Menon is satisfied he did the right thing by waiting for Rudd to blink his decision when his parents were ready to pull the plug.
"When a person is unconscious, they can't make their wishes known," he said. "Doctors need to get the best possible information to what they might desire. We have to take the family into account, but it's not as robust as from the patient."