A potentially life-threatening condition experienced at high altitudes resulting from oxygen deficiency in the blood and tissues
At high altitudes, the amount of oxygen in the air is reduced. The resulting low levels of oxygen in the blood and tissues cause symptoms such as tiredness, unsteadiness, headache, and nausea. This condition is known as altitude sickness. Altitude sickness usually affects mountaineers, but people flying from sea level to a high-altitude location may experience some mild altitude sickness upon arrival. The severity of the illness depends on how high and fast a person ascends, but altitude sickness does not normally occur below about 2,400 m (8,000 ft).
Symptoms may begin to develop about 6 hours after arriving at high altitude. Symptoms may include:
Tiredness and weakness.
These symptoms are usually mild and disappear within 1–2 days if you do not ascend further. In some people, more severe symptoms, including shortness of breath and vomiting, may develop within 36 hours. In rare cases, fluid may build up in the lungs (a condition known as high-altitude pulmonary oedema) and result in a cough with frothy sputum. Fluid may also accumulate in the brain (high-altitude cerebral oedema), causing the brain to swell, which initially results in clumsiness and difficulty in walking. If altitude sickness is left untreated, further symptoms may develop, including confusion, seizures, and coma, and the person may even die.
If you have mild altitude sickness, rest, painkillers, plenty of fluids, and a light diet should enable you to acclimatize to the altitude. A further ascent should not be attempted until all your symptoms have subsided.
In severe cases, a rapid descent to a lower altitude may be life-saving. Even descending only 300 m (1,000 ft) may lead to an improvement. If symptoms persist, hospital admission is necessary.
In severe cases, immediate oxygen therapy is necessary. If the lungs and brain are affected, a delay in treatment may lead to permanent brain damage and possibly death. Bed rest will be recommended, and the drug dexamethasone (see Corticosteroids) may be given to relieve the symptoms.
Most people treated for altitude sickness recover fully within 1–3 days. Even if the lungs and brain are affected, a full recovery is likely, although in this case treatment may be needed over a longer period of several days or weeks.
Good physical preparation and a high level of fitness are essential prerequisites for climbing at high altitudes. Ascents to high altitudes should be staged and gradual and should include intervals of a few days spent at intermediate altitudes before climbing higher.
Plenty of fluids should be taken on climbs. Occasionally, the drug acetazo-lamide may be prescribed beforehand to reduce susceptibility to altitude sickness. An oxygen supply should be part of the equipment for people climbing above 3,700 m (12,000 ft) because it may be necessary for treating unforeseen cases of altitude sickness.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.