There are real questions about near death experiences. The first is skeptics claims the brain is coping with death by creating a fantasy or dream to make it pleasant.
Yes, some people have suggested that some substance given off when the brain has little oxygen, triggers these 'experiences.'
I don't know.
I did have a 'near death experience' once ... or I think I did.
I was having my tonsils and adenoids out. (What was I? Eight? Nine?)
For that surgery, the hospital I was in still used ether as an anesthetic.
What I believe I remember is the classic tunnel of light, and 'me' somehow rising up to the ceiling from which I could see everyone, and hear voices quite clearly, at least for a moment or two.
The problem is that I've read a fair amount about 'near death experiences' and can't be sure I haven't conflated what I read with what I actually experienced. So I wouldn't take any of this to the bank.
NDE's are interesting, but it's hard to tell whether they really prove anything.
And therefore, I suppose, they don't.