Some people who survive cardiac arrest report experiencing some form of awareness during this time when their heart has stopped beating. In a new study in the journal Resuscitation, researchers aim to better understand what, if anything, goes on in the brains of cardiac arrest patients receiving CPR.
In interviews, some study participants reported experiences such as seeing deceased family members, feeling aware of the CPR and having dreams while their hearts were stopped. Brain scans showed that some patients exhibited brain activity that resembled consciousness during resuscitation, according to Scientific American’s Rachel Nuwer.
“There’s nothing more extreme than cardiac arrest, because they’re literally teetering between life and death; they’re in a deep coma and they don’t respond to us physically at all,” lead author Sam Parnia, who studies resuscitation at New York University, tells NBC News’ Theresa Tamkins. “What we’re able to show is that up to 40 percent of people actually have a perception of having been conscious to some extent.”
Researchers have previously studied near-death experiences, trying to gain insight into the last moments before life ends. A May study of four dying comatose patients found that two exhibited an increase in brain activity after they were taken off life support. And this summer, scientists identified a brain area involved in one’s physical sense of self, suggesting it might play a role in the floating feeling common to out-of-body experiences.
For the new study, scientists observed treatment of 567 patients who suffered cardiac arrest while in the hospital. In this state, blood flow to the brain and other organs stops. Nine out of ten people who go into cardiac arrest outside a hospital die, according to the National Heart, Lung and Blood Institute.
When patients went into cardiac arrest, medical personnel placed devices that measured brain oxygen levels and brain activity on their heads without impeding treatment, writes Scientific American. Of the 567 patients, 53 survived to discharge and 28 participated in interviews for the study. Patients received CPR for about 26 minutes on average.
Eleven of the interview participants—or approximately 40 percent—reported experiencing awareness during cardiac arrest. To supplement this arm of the study, which involved a relatively small number of patients, the researchers also collected 126 self-reported experiences of awareness during cardiac arrest from an existing database and from mailed-in responses. These people said they experienced weightlessness, reevaluations of life or feelings of moving toward a destination as if through a tunnel, and some reported memories of receiving CPR.
Additionally, around 40 percent of the 53 participants from whom researchers were able to gather brain activity had brain waves consistent with consciousness for a time. Though their brains had flatlined, they exhibited spikes in activity even up to one hour into the resuscitation, reports CNN’s Sandee LaMotte.
“I think that’s incredible,” Sheldon Cheskes, who studies cardiac arrest resuscitation at the University of Toronto and didn’t contribute to the findings, tells NBC News. “You would never have known that without being able to do that brainwave monitoring.”
However, the team did not find a connection between this surging brain activity and an experience of consciousness. “That is, those patients who had near-death experiences did not show the reported brain waves, and those who did show the reported brain waves did not report near-death experiences,” Bruce Greyson, a researcher at the University of Virginia who studies near-death experiences and did not contribute to the paper, tells CNN.
Though more research is needed to reach conclusions about near-death experiences, the findings could still impact medicine today. The research should “inform our humanity,” Lakhmir Chawla, an intensive care unit physician who did not contribute to the study, tells Scientific American. It should “compel clinicians to treat patients who are receiving CPR as if they are awake,” he adds, something “we rarely do.”