OK thanks...I did wonder if the headaches and vomiting were indications of a blocked valve....clearly not the case.
The headaches and vomiting, sever enough to have a "near death experience" can be explained on scientific grounds as the body reacts by producing endorphins.
Endorphins,PCP, LSD, Marijuana, cocaine, heroin and morphine all may cause distortions of reality, alterations of body image, and disorientation as to time and place. The near-death experience does not involve distortions of reality, but rather the perception of another reality superimposed over this one.
Best I can do ;-)