One in five people may recall near-death experiences after surviving cardiac arrest: Study

One in five people who survive cardiopulmonary resuscitation (CPR) after cardiac arrest may describe lucid experiences of death that occurred while they were seemingly unconscious and on the brink of dying, a first-of-its-kind study has found.

CPR is a lifesaving technique, consisting of chest compressions often combined with artificial ventilation, that's useful in many emergencies, such as a heart attack or near drowning, in which someone's breathing or heartbeat has stopped.

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The research, published in the journal Circulation, involved 567 men and women whose hearts stopped beating while hospitalised and who received CPR between May 2017 and March 2020 in the US and UK.

Despite immediate treatment, fewer than 10 per cent recovered sufficiently to be discharged from hospital, the researchers said.

Survivors reported having unique lucid experiences, including a perception of separation from the body, observing events without pain or distress, and a meaningful evaluation of life, including of their actions, intentions and thoughts towards others, they said.

The team found these experiences of death to be different from hallucinations, delusions, illusions, dreams or CPR-induced consciousness.

The research, presented at the American Heart Association's Scientific Sessions 2022 on November 6 in Chicago, US, also included tests for hidden brain activity.

A key finding was the discovery of spikes of brain activity, including so-called gamma, delta, theta, alpha and beta waves up to an hour into CPR.

Some of these brain waves normally occur when people are conscious and performing higher mental functions, including thinking, memory retrieval, and conscious perception, the researchers said.

"These recalled experiences and brain wave changes may be the first signs of the so-called near-death experience, and we have captured them for the first time in a large study," said Sam Parnia, an associate professor at NYU Langone Health.

"Our results offer evidence that while on the brink of death and in a coma, people undergo a unique inner conscious experience, including awareness without distress,” Parnia said.

Identifying measureable electrical signs of lucid and heightened brain activity, together with similar stories of recalled death experiences, suggests that the human sense of self and consciousness, much like other biological body functions, may not stop completely around the time of death, Parnia added.

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"These lucid experiences cannot be considered a trick of a disordered or dying brain, but rather a unique human experience that emerges on the brink death," said Parnia.

As the brain is shutting down, many of its natural braking systems are released. Known as disinhibition, this provides access to the depths of a person's consciousness, including stored memories, thoughts from early childhood to death, and other aspects of reality.

While no one knows the evolutionary purpose of this phenomenon, it clearly reveals "intriguing questions about human consciousness, even at death," said Parnia.

The researchers noted that although studies to date have not been able to absolutely prove the reality or meaning of patients' experiences and claims of awareness in relation to death, it has been impossible to disclaim them either.

They said recalled experience surrounding death now merits further genuine empirical investigation without prejudice.

Some 25 hospitals in the US and UK participated in the study, called AWARE II. Only hospitalised patients were enrolled to standardize the CPR and resuscitation methods used after cardiac arrest, as well as the recordings made of brain activity.

Additional testimonies from 126 community survivors of cardiac arrest with self-reported memories were also examined in the study to provide greater understanding of the themes related to the recalled experience of death.

Further research is needed to more precisely define biomarkers of what is considered to be clinical consciousness, the human recalled experience of death, and to monitor the long-term psychological effects of resuscitation after cardiac arrest, Parnia added.