Altitude sickness Dr Rob Hicks Altitude sickness is becoming a common problem as an increasing number of people are travelling further and going on activity holidays.

In this article

What causes it? Who's affected?

What are the symptoms? What's the treatment?

Can it be prevented?

The body's muscles and organs need an adequate supply of oxygen to function properly. As altitude increases, the percentage of oxygen in the air remains constant but the pressure decreases, meaning we breathe in fewer oxygen molecules with each breath.

This leaves the body short of its requirements and causes altitude sickness.

It's well known that mountaineers may be affected by altitude sickness, but anyone at high altitudes can experience symptoms. This includes people who fly to high-altitude destinations and those who go on walking and trekking trips.

How severely someone is affected by altitude sickness depends on how high they go and how quickly they ascend. It's unusual for altitude sickness to occur below 2,400m (8,000ft).

When altitude sickness occurs because the body is not getting enough oxygen, mild symptoms may include:

• Tiredness
• Headache
• Nausea
• Unsteadiness

For most people, symptoms start after about six hours of being at high altitude. As long as the person remains at the same altitude, the symptoms will usually disappear within one or two days.

Vomiting, chest pains and shortness of breath are signs that someone is affected more severely. These symptoms may take a day or two to appear.

Coughing up frothy sputum is a sign that fluid is collecting in the lungs, while clumsiness and difficulty walking can occur if the brain swells.

If severe cases of altitude sickness aren't treated, fits, confusion and coma may follow.

It's important not to ignore altitude sickness. If symptoms are mild, rest, fluids, a light diet and painkillers will enable the body to acclimatise. No further ascent should be attempted until all the symptoms have disappeared.

Descending to a lower altitude is often necessary when symptoms are more severe. If this fails to resolve symptoms, hospital treatment is needed. Any swelling of the brain will be treated with oxygen, rest and drugs.

Most people who are treated correctly for altitude sickness make a full recovery, usually within a few days. However, when the condition is more severe, treatment over a longer period may be necessary.

Problems with altitude sickness can usually be avoided if care is taken to prepare properly. Climbers, in particular, are all too aware of the importance of:

• Good physical fitness
• Staged ascents that allow time to acclimatise
• Drinking plenty of liquid
• Being aware of the possibility and the symptoms of altitude sickness
• Not ignoring symptoms of altitude sickness if they occur

This article was last medically reviewed by Dr Rob Hicks in October 2007