Light at the End of the Tunnel or Too Much Carbon Dioxide?

The connection between mind and body is never as ambiguous as when the body is near death. Reports of near-death experiences (NDEs) in people who suffer cardiac arrest or other life-threatening traumas are unexplained by current science. Theories of psychological, physiological, and transcendental causes abound, but none has defined the true source of the phenomenon. A new study, however, sheds light on the root of NDEs and reports that it may simply be a higher concentration of carbon dioxide in the body.

As many as 23% of survivors of cardiac arrest report memories of NDEs. Most share the same description: accelerated thought processes, peacefulness, joy, and encounters with mystical entities or deceased persons. NDEs have features associated with the phenomenon of dissociation — a psychiatric disorder in which a person’s identity becomes disconnected from bodily sensation. However, most people who report NDEs do not have a pathological mechanism contributing to the psychiatric condition.

The latest study examining NDEs, published in the journal Critical Care, examined 52 patients who survived an out-of-hospital cardiac arrest. Of these, 21% reported memories typical of NDEs. NDEs were more common in patients with higher levels of carbon dioxide on admission to the hospital. The connection with carbon dioxide suggests that NDEs might be associated with changes in the acid-base equilibrium of the brain. Previous studies have proved that changes in the brain’s equilibrium can trigger visions of bright lights and out-of-body experiences. Inhaled carbon dioxide has been studied as a psychotherapeutic agent and caused NDE-like experiences.

The current study found no association between NDEs and gender, level of education, fear of death, time to resuscitation, medication during resuscitation, or religious beliefs. However, patients who have reported previous NDEs are more likely to report another NDE, a finding that has been confirmed by other investigators.

Overall, little is known about dying, particularly the brain and levels of consciousness near the end of life. Cardiac arrest is considered the final stage in the dying process and is the closest physiological model of death that can be examined. As such, cardiac arrest survivors are commonly studied in the investigation of NDEs. Although most survivors do not report any memories for the events surrounding their cardiac arrest and resuscitation, the ones that do describe similar experiences. Additionally, many survivors are able to recall specific events during their resuscitation with vivid and lucid details that are confirmed by the resuscitation staff. Amazingly, many studies have indicated that the brain ceases to function during cardiac arrest, raising questions about the real connections between mind and body and the foundation of consciousness.

Consciousness is the ultimate enigma in the mind-body connection. The complex brain activity that correlates to consciousness may not be directly responsible for it and researchers cannot explain how it is that humans become aware of their surroundings and experience life apart from neural connections and interactions. Many believe that NDEs are proof that humans are more than just a collection of cells and neural processes and that humans have a soul or level of consciousness that is separate from the physical body. But, have the researchers in the current study debunked that theory in explaining NDEs with scientific details? Rationalizing the positive after-effects in overall well-being after an NDE with experimental values and statistics may be ignoring the bigger, transcendental questions of life and death.


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Klemenc-Ketis Z, Kersnik J, & Grmec S (2010). The effect of carbon dioxide on near-death experiences in out-of-hospital cardiac arrest survivors: a prospective observational study. Critical care (London, England), 14 (2) PMID: 20377847

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Jennifer Gibson, PharmD

Jennifer Gibson, PharmD, is a practicing clinical pharmacist and medical writer/editor with experience in researching and preparing scientific publications, developing public relations materials, creating educational resources and presentations, and editing technical manuscripts. She is the owner of Excalibur Scientific, LLC.
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