This type of brain injury (encephalopathy) is caused by partial (hypoxia) or total (anoxia) deprivation of the brain’s oxygen supply for longer than the compensatory mechanisms designed to prevent neuronal death can cope.
Oxygen is vital for the normal functioning of the brain, as the following figures illustrate:
“The brain represents 2% of our total body weight, but it consumes 20% of all the oxygen in our body.”
This fact is especially relevant given the following:
“The brain has limited capacity to store nutrients, which is why it demands a constant high level of oxygen supply.”
This is why brain tissue is widely accepted as being capable of surviving for up to four or five minutes of sustained anoxia. Once this time has elapsed, the anoxia will begin to cause damage to the brain tissue, and this damage will become more and more severe the longer the anoxia lasts. After 15 minutes of oxygen deprivation, more than 95% of the brain tissue will have been damaged.