Dr. John Murphy:

It is caused by the effect of a lack of oxygen on the brain. It was thought that it was like a road traffic accident in the sense that the injury occurs at the point of the impact, but that no longer appears to be the case. The way the brain works means that the injury that takes place as a result of a lack of oxygen happens over a period of hours, rather than in a single moment. That gives one an opportunity to move in and cool the body down to 32° or 33°, which is approximately 4° lower than normal, thereby allowing the brain to rest and recover. That seems to be the way it works. We cool the body down to 33.5° for 72 hours. It is quite complicated, but the results are very promising.