<unk>  refers to deprivation of oxygen supply to brain tissue.  Mild or moderate<unk>  is sometimes known as diffuse<unk> . It can cause confusion and fainting, but its effects are reversible. Total deprivation of oxygen to the brain is called<unk>  anoxia. Extended periods of<unk>  can lead to brain death or permanent brain damage.
Most cases of<unk>  are caused by a sudden change in brain oxygen levels. The body can normally respond to mild gradual changes in blood oxygen with little or no noticeable effect on brain function. The acclimatization process used by high altitude climbers is an example of such adjustment.
The presence of<unk>  symptoms indicates that the brain has been overwhelmed by a change in its oxygen supply.  Consequently, even mild symptoms of<unk>  require immediate medical attention.
Cerebral hypoxia
Oxygen toxicity
Nitrogen narcosis
Cerebral edema
Positional asphyxia
Respiratory losses
Hypothermia
Brain ischemia