Altitude illness includes a number of conditions that may occur in individuals travelling to high altitude, usually above 2,500 metres (8,200 feet). Most trips to altitude can be enjoyed safely if sensible precautions are taken. High altitude is defined as an elevation above 1,500m and can be divided into the following categories: high altitude 1,500 to 3,500m, very high altitude 3,500 to 5,500m and extreme altitude above 5,500m.
If an individual ascends gradually to high altitude, their body is usually able to adjust to the reduced oxygen levels. This process is known as acclimatisation. If ascent is too swift, then acclimatisation may not occur rapidly enough and altitude illness may follow.
Altitude illness includes: acute mountain sickness (AMS), high altitude cerebral oedema (HACE) and high altitude pulmonary oedema (HAPE). Severe AMS, HACE and HAPE are life-threatening conditions that need urgent attention.
The key to preventing high altitude illness is gradual ascent with regular rest days. Medications may be used to help prevent altitude illness in certain individuals. People with pre-existing medical conditions should consult with their healthcare provider prior to travel.