Cooling the body down is thought to slow tissue damage
Scientists have developed new ways to cool heart attack and stroke victims' brains to protect them from brain damage.
UK doctors believe that cooling could save lives by slowing the release of harmful chemicals from nerve cells, and many hospitals have adopted the idea.
Among the inventions, reported in New Scientist magazine, is a cap that blows cold air across the scalp.
Other innovations include a chilling nasal spray and an icy lung injection.
Many intensive care units across the UK now use cooling techniques to help heart attack patients after two major research studies showed significant benefits.
This "therapeutic hypothermia" is normally induced using cooled pads, ice packs or even injecting chilled saline liquid into the blood stream.
However, researchers are hunting for ways to achieve the necessary 4C drop more efficiently - or targeting only the brain itself.
The first of the new devices, developed at the University of Edinburgh, is a cooling helmet which works by passing cold air across the scalp, exploiting the dense network of blood vessels there.
Tests on volunteers, reported in The British Journal of Anaesthesia suggested that the hood was able to cool the brain by 1C per hour.
In the US, scientists are working on other quicker ways to achieve this, one by spraying a fine mist of droplets deep into the nasal cavity.
The liquid used, perfluorocarbon, evaporates rapidly, taking heat away from the area, and cooling the brain as a result - by up to 2.4C per hour.
A trial in pigs suggested this might not just reduce the chance of brain damage, but also improve the chances of successful resuscitation.
Other more radical ideas being trialled in the US involve squirting an icy "slurry" into the entrance to the lungs.
This is potentially the fastest, achieving the target four degree drop in just fifteen minutes, although again, it has only been tested on pigs so far.
Dr Richard Lyon, also based in Edinburgh, is conducting a study looking at the temperature of heart attack patients, with possible aim of testing the idea that early cooling - perhaps delivered by paramedics, might be the key to the best outcome.
He said: "In many cases, cooling would not happen until the patient reached intensive care, which could be several hours after the heart attack.
"Significant damage may already have happened by then."
He said that in these circumstances, the cooling method would have to be suitable for paramedic use - and the chilled saline solution, rather than a more complex device might fit the bill better.
He said: "Another issue is that selectively cooling the brain is not necessarily going to be effective against brain damage following a heart attack. You may need to cool the whole body."
However, he said that cooling had the potential to be a major lifesaver: "You have to treat 30 patients with clot-busting drugs after a heart attack to save one life - with cooling it is more like six."