Penny Sartori said some people recalled meeting dead relatives
An intensive care nurse from Swansea has published an academic book about near death experiences following 10 years of research.
Penny Sartori, who works at Singleton and Morriston Hospitals in Swansea, has 15 accounts, mainly from heart attack patients, of near-death experiences.
They include out-of-body occurrences, reports of a tunnel leading to a bright light and meeting dead loved ones.
The book, costing £85, is intended for academic study and college libraries.
Ms Sartori decided to launch her formal study in 1998 after working closely with critically-ill patients throughout the 1990s and discovering there was very little reference data available for nurses and other healthcare workers.
She spent five years compiling the study, three years writing it up and two years preparing it for publication. The book is called Near Death Experiences of Hospitalized Intensive Care Patients, a Five Year Clinical Study.
She found that people who went through out-of-body experiences floated above themselves and were able to accurately recount what had happened in the room even though they were unconscious and their eyes were closed.
"People also reported travelling down a tunnel towards a bright light," she said.
"Some reported meeting a figure who told them their time had not yet come, and others said they met dead relatives and communicated with them by telepathy."
In another case a patient reported encountering a dead relative who gave a message to pass on to another member of the family who was still alive.
Ms Sartori said the information had stunned the receiver because it had been a secret and it was impossible the patient had prior knowledge of it.
Near-death experiences were typically often explained away as the effect of endorphins, abnormal blood gases or low oxygen levels, she said.
However, the study measured these and took them into account when researching the patients' reports.
"All the current sceptical arguments against near-death experiences were not supported by the research," she said.
In one case a critically-ill patient, who also had cerebral palsy, awoke from a near-death experience able to use his right arm normally, even though it had been bent and contracted since birth.
"It shouldn't have been possible without an operation to release his tendons, but he could open his arm freely," said Ms Sartori.
Some patients reported floating back into their bodies after nearly dying, and for others it was a sudden snap back.
"Some patients reported having their entire lives flash by them in an instant," she said.
While she found 15 patients reporting near-death experiences, Ms Sartori believes it could be more common but that some patients' ability to recall the event fails shortly after they pass the critical episode and regain consciousness, like a dreamer forgets a dream.
She now intends to continue her research into the phenomenon and is developing a private theory, not included in her book, about what could be happening to these patients.
"I don't think it's quite as simple as life after death," she said.
"It's what consciousness is and how we define it. We are entering an exciting time researching consciousness.
"Current science says it is a by-product of the brain. But it may be that consciousness is around us and the brain might be a mediator, an antenna, instead of controlling consciousness.
"It is a fascinating subject and I'm looking forward to continuing my research," she added.