Heart attack patients who have seen the light during clinical death may offer answers to one of life's most baffling questions: what happens when we die?
The Aware (Awareness during Resuscitation) project has been launched by the University of Southampton to examine near-death experiences in heart attack survivors.
Following an 18-month testing phase in UK hospitals, the largest ever international study in the field has now been expanded to three years.
It is set to examine 1,500 heart attack patients in 25 UK and US hospitals to see if they experienced out-of-body experiences while they had no heartbeat or brain activity.
To test their experiences during this time, otherwise known as clinical death or cardiac arrest, researchers have set up shelves in participating hospitals which hold images that can only be seen from above the ground.
Patients will then be asked to recall any memories from the time of cardiac arrest to see if they experienced any accurate out-of-body experiences or merely "illusions".
The project is led by Dr Sam Parnia, an intensive care doctor and expert in the field of consciousness during clinical death, who is a visiting technician at the University of Southampton.
He said: "Contrary to popular perception, death is not a specific moment.
"It is a process that begins when the heart stops beating, the lungs stop working and the brain ceases functioning - a medical condition termed cardiac arrest."
He explained cardiac arrest could last from a "few seconds to an hour or more", in which time a patient's life could still be saved.
"What people experience during this period of cardiac arrest provides a unique window of understanding into what we are all likely to experience during the dying process", he said.
Participating hospitals include Southampton University Hospitals NHS Trust, Hammersmith and Charing Cross, and Swansea's Morriston, among others.
Collaborators in the US include Indiana State University, Rosalind Franklin University of Medicine and Science, Drexel University, Brooklyn Medical Centre, the University of Virginia, Wayne State University and New York University, as well as Vienna General Hospital in Austria.