My experience with this topic was a health problem I had 2 years ago while I was training for running a full marathon.
I was not near the death according to the doctor, but I thought it was my time to go...I have never been so afraid and my wife though the same, actually she thought that I was dead.
She found me on the bathroom floor in the middle of the night, eye opened but not conscious. All the floor was full of vomit and shit and I was not answering....for few minutes.
When I came back, I thought that I was about to die...we call the ambulance and straight to the nearest hospital.
The cause was a big dehydration during my run and an explosive diarrhea.
I've never been more scared.