While in extended CPR during cardiac arrest, patients showed no outward signs of consciousness—but scientists did record brain activity in those individuals.
BY CAROLINE DELBERT
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A landmark study reports the brain activity of patients in extended CPR during cardiac arrest.
Patients showed no outward signs of consciousness, but exhibited brain waves and even dreams.
Just 10 percent of patients survive cardiac arrest, making this study complex to design and complete.
Patients’ brain waves, along with recollections of their lives, could finally explain what we’ve typically called “near-death experiences,” (NDEs) scientists say in new research.
Using an experiment design they began developing in 2015—five years before the final, full version of the study was finally completed—the scientists rigged up people who experienced cardiac arrest. This carefully performed study is part of an area of medicine and research focused on resuscitation, using methods like CPR and defibrillation. And due to the sensitive nature of trying to study people who are experiencing cardiac arrest, something that only about 10 percent of patients survive, this kind of work has a ton of value for people who are interested in near-death experiences and other edge cases of brain activity.
The study, published earlier this year in the peer-reviewed journal Resuscitation, involved a combined 25 hospitals with affiliations in Georgia, New Jersey, New York, Ohio, Pennsylvania, Texas, Virginia, Bulgaria, and England. For their research experiment, participating personnel at all 25 hospitals had setups of tablet computers and headphones at the ready. If a patient in the hospital experienced cardiac arrest, the research staff fitted them with the tablet and headphones.
Each tablet showed patients one of ten randomized images, while the headphones played one of three words: apple, banana, or pear. This rig was mounted above each patient, out of the way of medical personnel trying to resuscitate them with CPR. Patients were also fitted for electroencephalography (EEG) to measure brain activity, and had their brain oxygen monitored.
Logistical Challenges
The researchers say this study is “first of a kind,” and that makes sense. Medical staff are trying to save people’s lives, and without a lot of thought and planning, it’s not possible to measure anything else happening while they’re attempting resuscitation. Researchers also needed quantity on their side, because such a slim percentage of people survive cardiac arrest. On medical TV dramas, showrunners love to revive patients and depict dramatic resuscitations, including ones that happen minutes after a patient has gone into arrest. But oxygen in the brain and other factors start to dramatically fall right away, leading to permanent damage in some survivors. For that reason, the scientists gave survivors a set of cognitive tests before including them in the study.
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Is Consciousness Everywhere All at Once?
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What Do You See When You Die?
In the introduction of their new paper, the researchers state that between 350,000 and 750,000 cardiac arrests occur in the United States each year. That’s a lot. It’s between about 1,000 and 2,000 per day, and per the researchers’ estimate of 10 percent survival, only about 100–200 patients survive cardiac arrest each day, and they’re spread out among over 6,000 hospitals in the United States. To gather enough cardiac arrest survivors to make a statistically significant study, researchers had to combine a lot of human power at a lot of hospitals. Their data set is drawn from three years’ worth of observations at 25 hospitals.
For their study, they observed a total of 567 in-hospital cardiac arrests. Fifty-three of these patients survived, 28 of whom were able to complete screening and interviews after their cardiac arrests. (If nothing else, the numbers in this study should be a shock of cold water about health risks and cardiac arrest. On top of existing figures, about 18 million American adults now report having long COVID, including many who have cardiovascular complications.)
People who talk about near-death experiences are usually referring to a specific format, the way talking about an “alien abduction” puts a specific idea in our minds of what someone is likely going to mention next. These things are very cultural. Hoaxes like The Boy Who Came Back From Heaven have reinforced a kind of NDE where someone is drawn into a tunnel of light, and their grandparent comes out to hold their hand. If these experiences are fueled by brain activity, albeit in extreme and unusual circumstances, it makes sense that they have elements of suggestibility and subconscious thought. Even if what takes place is a spiritual event, someone is still seeing it in their mind and with their eyes closed. How concrete are even your most cohesive dreams?
In the study, just 28 people of 567 total both survived cardiac arrest and were able to complete the cognitive evaluations and surveys. Altogether, 4 in 10 of those patients recalled “some degree of consciousness” following CPR. Of those 28, 11 people said they had memories or similar sensations from during their minutes of cardiac arrest. Six people, or 21.4 percent of those surveyed, experienced “transcendent recalled experience of death (RED).” Three reported something like dreams. None of the people exhibited signs that they were actually conscious, like moving around.
One patient said they’d seen their father. One felt they were standing next to their bed and watching their body receive CPR. One heard their deceased grandmother tell them to “go back.” Some remembered the moments before they were finally revived into consciousness. The dreams were, well, dreams: “Then, I walked into a puddle… When I got out of the puddle, I was not wet and I sort of melded into the pavement…”
What Does This Mean?
It’s important to remember that this field of research is tiny, meaning this study is not comparable with anything else right now. And while the 28 surveyed people do represent years of careful preparation and work, that’s still a tiny number. There’s little to be gleaned from the overall figures except that other scientists may feel encouraged to do their own studies in the future. But it’s significant that some people in the study did show brain activity during the resuscitation period. This continued up to 60 minutes after cardiac arrest and resuscitation began.
“Although doctors have long thought that the brain suffers permanent damage about 10 minutes after the heart stops supplying it with oxygen, our work found that the brain can show signs of electrical recovery long into ongoing CPR,” corresponding author Sam Parnia said in an NYU statement. And because this continuing brain activity is a challenge to conventional wisdom, it could explain the quite unified themes many people report during near-death experiences. It’s definitely a reason to do further research.
The attempts to guide or influence memories using images or sounds were almost completely unsuccessful. One person out of 28 identified the three spoken words, and none identified the images. In a way, this reinforces that what was happening was deep inside the brain. It points to a way that some kind of consciousness may endure even when, so to speak, the lights are out in the rest of the brain.
Cardiac arrest, mechanically different from a heart attack, means that blood flow in the body has shut down. This is why resuscitation, like CPR, is so important and so urgent. The brain experiences progressively worse injuries from the absence of fresh oxygen via blood flow, but chest compressions and even mechanical devices can keep some blood moving while doctors work to revive patients. (Doctors do not agree on exactly how chest compressions make blood flow.)
One point of comparison or contrast could be people with obstructive sleep apnea. In a 2019 review, researchers found that reports of dreams and especially nightmares among apnea patients were quite conflicting overall, but reflected that people who used continuous positive airway pressure (CPAP) machines reported fewer nightmares. Could it be that something about the change from an ideally oxygenated brain to a less oxygenated one fires off a change in consciousness?
In apnea patients, the feeling may be more like urgency and panic, leading to nightmares. But in extended cardiac resuscitation, it seems more like peace.
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CAROLINE DELBERT
Caroline Delbert is a writer, avid reader, and contributing editor at Pop Mech. She’s also an enthusiast of just about everything. Her favorite topics include nuclear energy, cosmology, math of everyday things, and the philosophy of it all.
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