A Critique of the NDE discussion from the Skeptics’ Guide to the Universe Podcast #249

by Keith D. Wood

I recently had the opportunity to listen to the Skeptics’ Guide to the Universe Podcast #249.  In this podcast, the host Dr. Steven Novella discussed NDEs and the recent Slovanian CO2 study.  James Randi was among several contributing guests on this podcast and he also offered insight and commentary.

The following is a critique of the discussion, with specific focus on omissions and key mistakes that were made regarding relevant data and research.

1. Dr. Novella claimed that typical NDEs are remarkably similar to oxygen deprivation of the brain.  He also claimed that ALL of the components can be induced by medications or brain stimulation.

Dr. Novella gave the usual descriptions for NDEs and went on to say that these experiences are remarkably similar to what happens to the brain when it is deprived of oxygen.  In the same sentence, he claimed that all of the components of the NDE experience can be induced with medications and magnetic stimulation of the brain.  He also indicated that he has treated patients who had NDE experiences while having seizures.

Source: Skeptics’ Guide to the Universe Podcast #249.              Time: 10:09

“but, skeptical neuroscientists like myself and others, would point out that these experiences are remarkably similar to what happens to the brain when it is deprived of oxygen and in fact we can induce ALL the components of that experience, floating outside one’s body for example, ah … with either medications, now we can do it by using transcranial magnetic stimulation to turn off parts of the brain, um…I’ve had patients who have had that experience while having a seizure .”

Counterpoints and Discussion:

Dr. Novella mixed several different theories and claims into this statement.  For the purpose of clarity and debate, I separated the claims as follows:

a. Oxygen deprivation of the brain can induce NDEs:

This is probably the oldest and most worn out NDE theory.  There are countless studies that show the effects of oxygen deprivation or cerebral hypoxia.   You can look at studies that describe oxygen deprivation in many different situations and none of them seem to fit the core components of NDE experience.

Let’s explore the reported symptoms of oxygen deprivation in the following scenarios, to see if they match the NDE experience:

i. General symptoms of oxygen deprivation:

  • Change in attention (inattentiveness)
  • Poor judgment
  • Uncoordinated movement
  • Memory Loss
  • Complete unawareness and unresponsiveness (coma)
  • No breathing
  • No response to light

My Conclusion: Doesn’t match reported NDE experiences.


Cerebral Hypoxia

Cerebral hypoxia Defined

ii. Oxygen deprivation in pilots:

  • Dizziness
  • Trouble comprehending instructions
  • Inability to focus
  • Tunnel Vision (not tunnel experience)
  • Feeling unsafe

My Conclusion: Doesn’t match reported NDE experiences.


High-altitude oxygen deprivation

iii. Oxygen deprivation in patients with lung disease:

  • Panic attacks
  • Anxiety
  • Confusion
  • Easy fatigue
  • Lethargy
  • Shortness of breath
  • Sleepiness

My Conclusion: Doesn’t match reported NDE experiences.


Journal of Family Practice – COPD: How to manage depression and anxiety

Respiratory acidosis

iv. Long term effects of Oxygen deprivation to the brain:

  • Short term memory loss
  • Decline in executive functions
  • Difficulty with words, also known as anomia
  • Visual disturbances, such as cortical blindness

My Conclusion:
Doesn’t match reported NDE experiences.


Hypoxic-Anoxic Brain Injury

Other related examples:

  • Self induced oxygen deprivation (Choking Game): Doesn’t match
  • Oxygen deprivation in mountain climbers: Doesn’t match
  • Oxygen deprivation in stroke patients: Doesn’t match

b. Medication can induce NDEs:

I’m guessing Dr. Novella is alluding to the Ketamine model for NDEs.  There is nothing new about this theory and while Ketamine seems to produce similar experiences in some users, they do not appear to be uniform and universal like the NDE.  Many users of Ketamine also report bad and distorted experiences and vow to never repeat their use of this drug.  Some reports of good and bad Ketamine trips can be read at this website.  Erowid Experience Vaults:

It seems that most serious NDE researchers have looked at the Ketamine model and do not feel that it explains the NDE.  In fact, Karl Jansen, probably the most noted Ketamine researcher, later changed his views regarding Ketamine and considered it to be more of a trigger/doorway to something more.

His exact quote:

“I am no longer as opposed to spritual explanations of these phenomena as this article would appear to suggest. Over the past two years (it is quite some time since I wrote it) I have moved more towards the views put forward by John Lilly and Stan Grof. Namely, that drugs and psychological disciplines such as meditation and yoga may render certain ‘states’ more accessible. The complication then becomes in defining just what we mean by ‘states’ and where they are located, if indeed location is an appropriate term at all. But the apparent emphasis on matter over mind contained within this particular article no longer accurately represents my attitudes. My forthcoming book ‘Ketamine’ will consider mystical issues from quite a different perspective, and will give a much stronger voice to those who see drugs as just another door to a space, and not as actually producing that space”.


The Ketamine Model of the Near Death Experience
Erowid Experience Vaults:

c. Magnetic stimulation can induce NDEs:

Dr. Novella did not indicate what studies he was specifically referring to.  However, I’m assuming that he was referring to studies like Persinger’s God Helmet and brain stimulation research done by scientists such as Olaf Blanke.

When you look at the experiments in this area conducted by Olaf Blanke, you see that the experiences do not closely match the NDE.  Some of Blanke’s test subjects reported sensations of feeling disconnected from their bodies, but did not report the other core components of the NDE.  In fact, one patient in Blanke’s research reported a hallucinatory experience, in which her limbs appeared like they were shrinking and growing.

Pin Van Lommel addressed the magnetic stimulation claim in his article: A Reply to Shermer; Medical Evidence for NDEs

The Out of Body Experience; Olaf Blanke

Out of Body Experiences
d. Seizures can induce NDEs:

Some people who suffer from temporal lobe seizures have reported experiences similar to NDEs.  However, there seems to be mixed opinions among researchers as to whether or not these experiences truly resemble NDEs.

Dr. Melvin Morse suggested a model which theorizes a connection between the right temporal lobe (the God Spot) and non locality.  He also cited a handful of studies which indicated similar experiences between NDEs and temporal lobe seizures. However, in his book “Light and Death”, Dr. Michael Sabom discounts the seizure NDE link.  He cites a rather large study of epileptic patients conducted by Dr. Denis Williams, which showed that 91% of the seizures were accompanied by fear, depression or displeasure.  The study further showed that while 9% of the seizures were reported as being pleasant, the emotions did not match the core NDE experience.  Dr. Sabom also quotes Dr. Ernst Rodin, Director of the Epilepsy Center of Michigan, as follows:

“The hallmarks and nuclear components of NDEs are a sensation of peace or even bliss, the knowledge of having died, and, as a result, being no longer limited by the physical body.  In spite of having seen hundreds of patients with temporal lobe seizures during three decades of professional life, I have never come across that symptomatology as part of a seizure.”

Dr. Bruce Greyson also downplayed the link between seizures and NDEs, in his article, “Near-death experiences: clinical implications“.


Near Death Experiences: Dr. Michael Sudduth
Temporal Lobe Epilepsy
Light and Death: Michael Sabom
Dr. Melvin Morse: God Spot
Near-death experiences: clinical implications

2. Dr. Novella claims that NDEs are culturally specific in nature.

Source: Skeptics’ Guide to the Universe Podcast #249.             Time: 11:34

“With near death experiences, they do sort of fit in around the edges, culturally specific experiences, so Christians have a Christian Near Death Experience.”

Counterpoints and Discussion:

I was surprised at this statement.  One of the most interesting observations about NDEs is that they seem to be cross-cultural.  Atheists, Christians, Muslims, Buddhists, etc., all report the same core NDE experiences.  It is important to note, that children who are very young and not heavily indoctrinated into a specific religion, report the same experience that adults report, regardless of their culture.

Dr. Novella is correct that people tend to describe the being of light, in terms of their own culture and background. This would be expected, as they can only draw from the words that they are familiar with.  However, this should not be confused with their description of the core NDE experiences.

Dr. Novella backed off this statement slightly based a guest’s question.  He stated the following:

Source: Skeptics’ Guide to the Universe Podcast #249.             Time: 12:24

“that’s one of the common cross-cultural elements is the tunnel vision, floating outside the body. The real hard core neurological stuff is cross-cultural. But then you know, seeing an angel or something more cultural gets filled in.”

Data Sources:

Near Death Experiences: An Outline by Dr. Michael Sudduth

Culture and NDEs

3. Dr. Novella refers to the Slovenian study regarding C02 levels and NDE’s

Dr. Novella makes some key mistakes in his description of this study.  They are as follows:

a. He claims that the patients in the study suffered cardiac arrest outside the hospital, but were resuscitated in the emergency room.  Here is his exact quote:

Source: Skeptics’ Guide to the Universe Podcast #249.             Time: 12:56

“They had cardiac arrest outside the hospital, and then were brought in and resuscitated in the emergency room.”

Counterpoints and Discussion:

He is clearly wrong.  The patients were successfully resuscitated outside the hospital and were admitted to intensive care units.  This is important, because the C02 levels were not checked until they were admitted and had already been resuscitated outside the hospital.

Note the following excerpt from the original study:

“We studied out-of-hospital cardiac arrest survivors who were successfully resuscitated in out-of-hospital settings and consecutively admitted to intensive care units”

a. Correction 5/16/2010:

After re-reading the Slovenian CO2 study, I would like to point out a partial mistake on my part regarding the following above sentence:.

“This is important, because the C02 levels were not checked until they were admitted and had already been resuscitated outside the hospital.”

It appears that the petCO2 levels were measured during CPR and were then compared to the pCO2 levels in the blood after hospital admittance.

Data Sources:

Slovenian C02 Study

b.     Dr. Novella goes on to explain that his big problem with the study is the premise that people who are having the experience are having them while undergoing CPR.     Here is his exact quote:

Source: Skeptics’ Guide to the Universe Podcast #249.             Time: 14:55

“the major problem that I have with it, is the premise that the people who are having the experience are having them while they’re undergoing CPR, because that’s when they measured the oxygen, the carbon dioxide and everything else. That’s when their C02 levels were elevated”

Counterpoints and Discussion:

He is clearly wrong in this statement as well.  He again makes a critical mistake by claiming that doctors measured the oxygen and carbon dioxide levels during CPR.  The blood gas analysis was done after the patients were admitted and already successfully resuscitated outside the hospital, not during CPR.  Therefore, we don’t know what the C02 levels were during CPR.

See this excerpt from the original study:

“Only the blood sample analysis that was performed on the samples taken in the first five minutes upon the admission of the patients to the hospital was taken into account.”

Correction 5/16/2010:

After re-reading the Slovenian CO2 study, I would like to point out a partial mistake on my part with regard to the following above sentences:

“He again makes a critical mistake by claiming that doctors measured the oxygen and carbon dioxide levels during CPR. ”

“Therefore, we don’t know what the C02 levels were during CPR.”

It appears that the petCO2 levels were measured during CPR and were then compared to the pCO2 levels in the blood after hospital admittance.

However, it is important to note that the petCO2 levels were actually lower than the post admittance pCO2 levels in both the NDE and non-NDE groups.  Also, both of these levels were either lower or within normal range.  Therefore, I would suggest that that data does not support any suggestion that the NDE may be due to CO2 buildup during or after cardiac arrest.

Data Sources:

Slovenian C02 Study

c.     Dr. Novella then presents the theory that perhaps the NDE is happening at a later time, when the patient’s brain is slowly recovering.  He further posits that by the time they become conscious, the patient conflates all of the memories that occurred during the ordeal and while they were delirious.  Here is his exact quote:

Skeptics’ Guide to the Universe Podcast #249.             Time: 15:09

“but what if the experience that they’re having is occurring an hour later or a day later, while their brains are slowly recovering from the experience. Then by the time they become conscious, they conflate all those memories, they have no time sense. To them it just happened, right. And just happened, so it must have happened while they were getting CPR, they were floating outside their body, but they could have incorporated memories from the last two days when they were delirious, when their brain was slowly recovering”

Counterpoints and Discussion:

Many scientists and even posters in the Skeptiko forums have cited Occam’s Razor as a means for determining likelihood among theories.  Lets apply Occam’s Razor to the following two scenarios and see which one seems more likely:

Scenario A:

During cardiac arrest, some patients experience a form of consciousness that appears to be separated from the physical body.  Because of this separation, many of these patients can accurately describe their resuscitation procedures and events from a perspective that would not normally be possible.

These patients report the same core NDE experiences as millions of other near death survivors.

Scenario B:

The brain stores fragments of delirious memories during cardiac arrest, resuscitation and recovery.  This would include accurate sensory perceptions, overheard conversations, awareness of detailed medical procedures being performed and specific personnel present during resuscitation.  At some point in time during the patient’s recovery, the brain chooses to reconstruct these fragments into a lucid, accurate and well-formed NDE that has lasting transformative effects on the patient.

Not only does the brain accomplish this restructuring, but it does so in the very same manner millions of times, given the number of people who have experienced NDE’s.

And the winner is? I would say A, according to Occam’s Razor.

d.     Dr. Novella makes the same mistake as other readers by describing the patients as having “high” levels of C02.

Source: Skeptics’ Guide to the Universe Podcast #249.            Time: 14:19

“Is the high CO2 causing the brain to have this experience?”

They did not have high levels of C02; they had very slightly higher levels than the non-NDE group.  Normal C02 levels are around 6.0kPA.  The NDE-Group averaged 6.6kPA, which is not high enough to even be considered abnormal.

In addition, people who suffer from lung disease, sleep apnea and even scuba divers, deal with C02 levels much higher than what was reported in this study.  Yet, you don’t hear reports of people in those groups having spontaneous NDEs.

Data Sources:

Normal PC02 levels
Sleep Apnea and Hypercapnia
Hypercapnia in the obstructive sleep apnea
Hypercapnia or Carbon Dioxide and Diving (part I)
Hypercapnia Defined
Respiratory acidosis

e.     Dr. Novella makes the claim that the study showed that the C02 level was highly predictive of those who had NDE’s.

Source: Skeptics’ Guide to the Universe Podcast #249.            Time: 13:45

“Where as the CO2 very highly predicted who would go on, who had a near death experience and who didn’t”

Yet, as Dr. Bruce Greyson pointed out in a recent email to Alex, if the authors would have corrected their statistics to account for random chance, none of the differences would have been significant. In all fairness to the authors, they were very careful to note the following weaknesses in their own study:

“Our study suggests that some physiological factors or processes might be important in provoking NDEs. On the other hand, the experiences induced by neurophysiological processes mostly consist of fragmented and random memories and confused experiences unlike the real NDEs that are clear, highly structured and easily recalled.”

“The number of patients in the sample is the main weakness of our study. Therefore, some important differences might have been overlooked and the results should be interpreted with care.”

Data Sources::

Slovenian C02 Study
Dr. Greyson Email to Alex as posted in Skeptiko Forum Thread

4.     James Randi, mocks the NDE experience by relating to what he claims was his NDE experience.

James Randi Claimed he had a NDE as the result of a spinal injury he suffered during a car accident.  He indicated that he remembered being in a tunnel with a white light at the end.  He further commented that he remembered moving down a tunnel with white lights and could feel and hear a rumbling sound.  He then explained that he finally realized he was being wheeled down a hospital hallway and was feeling the rumbling of the gurney wheels as well as seeing the lighting fixtures in the ceiling.  He further indicated that the person at the end of the tunnel was the ambulance attendant who was standing at the end of the hallway.

Randi’s story can be found at the following time segment in the podcast.  It’s a lengthy quote, so I chose not to provide the excerpt.

Source: Skeptics’ Guide to the Universe Podcast #249.                  Time: 17:11

Counterpoints and Discussion:

This is both laughable and intellectually insulting at the same time.  Has he ever really read any NDE research?  Does he realize that his “experience” doesn’t even slightly resemble the experiences reported by NDE patients?   I’m hoping this was just an attempt at humor on his part and not a real analogy.

5.     James Randi attempts to draw a parallel between mistaking a stranger for his assistant and NDE components.

James Randi recounts a story where he was walking through a parking garage looking for
his assistant who was to give him a ride home.  He mistook another gentleman for his assistant and equated that with a hallucination and a wonderful transformative experience.

He went on to point out that many people think their perception is accurate, when a lot of times it is not.  Thus, he concluded that you cannot count on the accuracy of the NDE reports.

Source: Skeptics’ Guide to the Universe Podcast #249.              Time: 18:10

Huh?  This doesn’t make any sense to me.  He mistook a stranger for his assistant and
somehow this was a transformative experience that relates to NDEs!

Randi has a valid point regarding misperceptions.  However, in the case of NDEs,
many details are verifiable, right down to visual detail of medical procedures and personnel present during resuscitation.


I would like to conclude my critique by addressing the following statement made by Dr. Novella:

Skeptics’ Guide to the Universe Podcast #249.                        Time: 10:39

“There’s a lot of evidence sort of triangulating on the fact that this is probably a brain experience, not any kind of dualistic mind separate from body experience.”

Counterpoints and Discussion:

I’m not sure what triangulating evidence Dr. Novella is referring to, but I would argue that most of the current research doesn’t support his claim at all.  In fact, I would argue that there is nothing new about the claims against the NDE as a dualistic experience.  Consider the following NDE theories:

1.     Cerebral hypoxia

2.     NDE from CPR blood flow

3.     Final deathbed story

4.     Drug induced hallucinations

5.     Temporal lobe association

6.     CO2 / Blood gas involvement

If anything, I would argue that the triangulating evidence has shown that these theories do not adequately explain the NDE.