Psychologists have also offered explanations, which are much harder to test. French said one popular theory hypothesizes that a near-death experience is a way for the brain to disassociate from the extreme stress of dying and help a person cope.
A third faction, according to French, are theologians who say a near-death experience is a separation of spirit or consciousness from the mind.
Whitfield, who said she was an atheist before her near-death experience, takes this particular view.
Whitfield was 32 when a swimming pool accident knocked loose a vertebra in her lower spine. She was in the hospital recovering from major spinal surgery and strapped to a hospital bed when the accident with the ventilator occurred.
"They would come in with a ventilator three times a day," said Whitfield, author of "The Natural Soul."
"The ventilator malfunctioned, it didn't reverse, it just kept flowing," she said.
By the time nurses figured out what happened, air had filled her lungs and her intestinal tract to the point where she looked pregnant. Whitfield remembers she blacked out and when she woke up, she found herself outside of her hospital room in the hallway near the ceiling.
"I thought, 'If I stay out here (I'm) going to be in trouble'," said Whitfield. "That's how innocent I was to this whole thing."
Whitfield said she briefly saw her body below her before a darkness enveloped her. Her dead grandmother soon appeared and she relived, jointly, their history on earth together.
"That alone would have been enough to change me forever," said Whitfield. "I would stop telling people [nurses] because I would get upset and then they'd sedate me. They would tell me it was a hallucination, and I didn't' want to hear it was a hallucination."
A week later, Whitfield faced death again. A nurse positioned her face-down in her hospital bed to prevent bedsores. A nurse was supposed to come back in 20 minutes to move her upright, but nobody showed up. Whitfield was stuck in agony and had no idea how long she waited before she blacked out.
"At this point I saw myself as I was leaving my body. I saw myself in the circle bed. I looked up at the darkness and I saw myself as a baby in a crib," said Whitfield.
Whitfield said a benevolent force enveloped her, bringing an overwhelming sense of peace. She traveled with the force and relived scenes from her entire life up to that point. When she came to, she said the experience changed her life forever, but it took years before she told anyone.
"I agree when they [scientists] explain it on an anatomical way, but they can't explain what we go to when we experience this," said Whitfield.
Dr. Sam Parnia, an intensive care physician who studies near-death experiences, said he too sees the problem with trying to explain near-death experiences with a physiological process.
"One of the things that I've heard being bandied about is because we believe that such and such a chemical has been associated with a near-death experience, therefore NDE is a hallucination," said Parnia. "This is really fraught because every human experience is triggered off by some kind of chemical change in the brain."