Definitions of Mountain Altitude

Arbitrary classifications of the different mountain altitudes have been proposed; in these classifications, the term ‘high altitude’ generally refers to altitudes above 2,500 m. The definitions of high altitude are indicative of the risk of developing minor or major physiological alterations and the altitude sickness related to them. A physiological classification of high altitude proposes to identify as high altitude that mountain altitude in which the SaO 2 drops below 90%. This ‘physiological’ classification of high altitude appears to better take into account the various individual differences related to health status and speed of ascent.