Anoxia is the complete lack of oxygen to any tissue or organ in the body. Anoxic brain injury is when the brain is deprived of oxygen and blood flow, causing damage to the brain cells. The longer an individual goes without oxygen to the brain, the more damage occurs. Brain cells are extremely sensitive to oxygen deprivation and can begin to die within five minutes after the oxygen supply has been cut off. This can lead to permanent brain damage. For this reason, first responders must always administer oxygen as quickly as possible following an injury.