What is death?
Death occurs when the heart stops beating. We call this death by cardiopulmonary criteria and it is how death is defined for more than 95 percent of people. A person stops breathing and their brain shuts down, causing all life processes to cease. More recently with the birth of modern intensive care medicine and the ability to artificially keep people's hearts beating, doctors like myself can keep a patient's heart beating longer.
Where people may have suffered irreversible brain damage and brain death, this leads to a situation where the brain has died, but the person's heart is still beating, so legally, they are declared dead based upon irreversible brain death, or death by brain death criteria. This happens in a small fraction of the cases where people are declared dead.
For millennia death was considered an irreversible event and nothing could restore life. During the last decade, we've realized it's only after a person has died that the cells inside their body, including the brain, begin their own death process. We used to think that you had five or 10 minutes before brain cells died, from a lack of oxygen, but we now know that's wrong.
You have hours, if not days, before the brain and other organs in the body are irreversibly damaged after death. It's actually the restoration of oxygen and blood flow back into organs after a person's heart stops, but is then resuscitated that paradoxically leads to accelerated cell death. So, this accelerated secondary injury process is what we need to combat in medicine now.
What is a death experience?
I call it an "experience of death" because that's what it is. People report a unique cognitive experience in relation to death. They may have a perception of seeing their body and the doctors and nurses trying to revive them, yet feel very peaceful while observing. Some report a realization that they may have actually died.
Later they develop a perception or a sensation of being pulled towards a type of destination. During the experience, they review their life from birth, until death, and interestingly this review is based upon their humanity.
They don't review their lives based on what people strive for, like a career, promotions, or an amazing vacation. Their perspective is focused on their humanity. They notice incidents where they lacked dignity, acted inappropriately towards others, or conversely, acted with humanity and kindness.
They re-experience and relive these moments, but also, what's fascinating, which sort of blows me away because I can't really explain it, is they also describe these experiences from the other person's perspective.
If they caused pain, they experience the same pain that other person felt, even if they didn't realize it at the time. They actually judge themselves. They suddenly realize why their actions were good or bad, and many claim to see the downstream consequences of their actions.