what is anoxia?

Anoxia is a condition caused due to absence of oxygen supply to an organ or a tissue.
As at high altitudes the partial pressure of oxygen is low, the mole fraction (here the amount of oxygen present in air) is comparatively lower, the solubility of oxygen decreases in our blood, thus causing lesser supply of oxygen through blood capillaries to brain. This is the reason that prevents climbers to think clearly.