What is hypoxia and what can happen with prolonged hypoxia?

Hypoxia is the physical condition induced by an inadequate concentration of oxygen in the blood and the organs. The insidious danger of hypoxia is the subject’s unawareness of his deteriorating faculties which may actually be perceived as a feeling of well-being or euphoria. Prolonged exposure to moderate to severe hypoxia could result in brain damage to the extent of total intellectual deficiency. Note: there is a wide variability in individual tolerance.