Four minutes without oxygen will kill brain cells. This can bring on anoxic brain injury. Such a very short time deprived of oxygen, yet it can have an enormous effect on the rest of the victim's life.
Oxygen deprivation can have a great many causes.
Anoxic brain injury can be the result of cardiac arrest, cardiovascular disease, brain tumors, chest trauma, severe bronchial asthma, stroke and anesthesia accidents.
Failed suicide attempts, near-drowning, choking or suffocation, barbituate overdose, electrocution, exposure to carbon monoxide, are all events that can lead to anoxic brain injury.
Severe forms of anoxic brain damage can lead to coma, or a vegetative existence.
The person who suffers from mild to moderate anoxic brain injury is more fortunate. But they can still experience significant and massively difficult changes in their lives.
The production and function of neurotransmitters, which regulate much of our cognitive, emotional and physical abilities, will have been disrupted. The individual may then suffer from difficulties with thought processes, poor memory, and even changes in their personality and behavior.
Their intelligence is not necessarily affected, but the brain will very possibly be processing much slower than it used to. This can lead to all manner of frustration for the brain-injured person as they are often all too aware of their new limitations but are unable to change the new reality. They are faced with the challenge of learning new ways of dealing with their day to day lives.
The doctor involved in a case such as this may order tests to determine how severe the damage is, and what part of the brain has been hit. Head CT scans, MRI scans, EEG tests, SPECT scans may all be helpful. Evoked potential tests can evaluate the brain and spinal cord, and the nerve pathways from the eyes and the ears.
Rehabilitation may be an option depending on the type and severity of the damage. A physical therapist will help to retrain motor skills. This can help with walking, for instance. An occupational therapist can help in relearning or improving daily skills, like dressing.