Near-Death Experience = Overdose of CO2

near death experience, tunnel of light, handsFirst, scientists explained guardian angels. Now, a study of patients offers a scientific explanation for near-death experiences (NDEs).

As PhysOrg reports, between 11 and 23 percent of heart attack sufferers report the typical symptoms of a near-death experience (NDE). As the BBC notes, these symptoms often include:

. . . seeing a tunnel or bright light, a mystical entity, or looking down from the ceiling at the scene below in an “out of body” experience.

Others describe a simple but overwhelming feeling of peace and tranquillity.

Drugs and religion have usually been the explanations given for NDEs.

Slovenian researchers, led by Zalika Klemenc-Ketis of the University of Maribor, studied 52 consecutive heart attack cases in three major hospitals.

Eleven of the 52 patients had NDEs, with the common symptoms. They interviewed the patients and reviewed their records to determine whether they had any commonalities.

The patients lacked commonality in age, sex, ethnicity, religious belief, fear of death, level of education, recovery time, or drugs used in resuscitation.

The things they did have in common? Elevated CO2, and slightly elevated potassium levels in the blood.

The study report is currently being finalized. The provisional paper and abstract are available in the current issue of Critical Care, and a provisional abstract may be accessed HERE. The provisional abstract:


Near-death experiences (NDEs) are reported by 11-23% of cardiac arrest survivors. Several theories concerning the mechanisms of NDEs exist – including physical, psychological, and transcendental reasons – but so far none of these has satisfactorily explained this phenomenon. In this study, we investigated the effect of partial pressures of O2 and CO2, and serum levels of Na and K on the occurrence of NDEs in out-of-hospital cardiac arrest survivors.


A prospective observational study was conducted in the three largest hospitals in Slovenia. Fifty-two consecutive patients (median age 53.1 years, 42 males) after out-of-hospital cardiac arrest were included. The presence of NDEs was assessed with a self-administered Greyson’s NDE scale. The initial partial pressure of end-tidal CO2, the arterial blood partial pressures of O2 and CO2 and the levels of Na and K in venous blood were analysed and studied. Univariate analyses and multiple regression models were used.


NDEs were reported by 11 (21.2%) of the patients. Patients with higher initial partial pressures of end-tidal CO2 had significantly more NDEs (P < 0.01). Patients with higher arterial blood partial pressures of CO2 had significantly more NDEs (P = 0.041). Scores on a NDE scale were positively correlated with partial pressures of CO2 (P = 0.017) and with serum levels of potassium (P = 0.026). The logistic regression model for the presence of NDEs (P = 0.002) explained 46% of the variance and revealed higher partial pressures of CO2 to be an independent predictor of NDEs. The linear regression model for a higher score on the NDE scale (P = 0.001) explained 34% of the variance and revealed higher partial pressures of CO2, higher serum levels of K, and previous NDEs as independent predictors of the NDE score. Conclusions

Higher concentrations of CO2 proved significant, and higher serum levels of K might be important in the provoking of NDEs. Since these associations have not been reported before, our study adds novel information to the field of NDEs phenomena.

Other research on NDEs:

A 2006 study on NDEs found that patients who experience NDEs tend to have a less-clear boundary between conscious and unconscious states.

The US team said the same parts of the brain are activated when people dream as in near death experiences.

Near death experiences were defined by the University of Kentucky researchers as a time during a life-threatening episode when a person undergoes an out-of-body experience, unusual alertness or sees an intense light or feels a great sense of peace.

They found 60% of those who reported such experiences said they had experienced the REM state of sleep during periods of wakefulness.

Examples of this include waking up and feeling unable to move, having sudden muscle weakness in the legs and hearing sounds just before falling asleep or waking up that others do not hear, the team said.

In related news, a three-year, 1,500-patient study of NDEs, testing out-of-body experiences at 25 major hospitals in the US and the UK, is due to be completed in 2011:

Some people report seeing a tunnel or bright light, others recall looking down from the ceiling at medical staff.

The study, due to take three years and coordinated by Southampton University, will include placing on shelves images that could only be seen from above.

To test this, the researchers have set up special shelving in resuscitation areas. The shelves hold pictures – but they’re visible only from the ceiling.

Dr Sam Parnia, who is heading the study, said: “If you can demonstrate that consciousness continues after the brain switches off, it allows for the possibility that the consciousness is a separate entity.

“It is unlikely that we will find many cases where this happens, but we have to be open-minded.

“And if no one sees the pictures, it shows these experiences are illusions or false memories.”

So far, researchers haven’t released any preliminary data. No case studies of patients who actually see the pictures on the shelves.

What do you think will come of it? Will NDEs go the way of guardian angels . . . explained by science, but still believed in regardless?

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