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Overview:

• Altitude sickness mainly occurs at heights above 2500 metres
• The condition occurs because of the body trying to adjust to lower oxygen levels
• In rare cases, the illness can lead to life threatening conditions
• Symptoms of altitude sickness include headache, dizziness, nausea, loss of appetite
• Do not climb any higher if you develop altitude sickness
• Descend if you do not feel better after one day
• The drug acetazolamide (Diamox) can be used to help prevent altitude sickness

What is it?

Altitude sickness is a common problem for mountain climbers and travellers to some areas.

A high altitude is considered any height above 2500 metres (8000 feet) because altitude sickness is uncommon at heights lower than this. Healthy people can travel quickly to a height of 3500m (although some will get altitude sickness after arrival). People should not travel to heights much above 3500m directly from sea level.

More than 50 percent of travellers develop some form of altitude sickness at heights above 3500m, and most people will suffer from it if they quickly ascend to 5000m or higher. Anyone can get altitude sickness including those who are physically fit.

Patients with illnesses such as heart or lung disease or high blood pressure should obtain medical advice before travelling higher than 4000m.

Altitude sickness occurs because of the bodily changes in response to lower levels of oxygen at large heights.

In rare cases, altitude sickness can lead to two life threatening conditions such as pulmonary oedema (fluid on the lungs) and cerebral oedema (swelling of the brain) which need to be treated as an emergency.

What are the symptoms?

The main indication of altitude sickness during ascent is a painful headache with one or more of the following symptoms:

• Loss of appetite, nausea or vomiting
• Dizziness
• Sleeping problems
• Fatigue or weakness
• Confusion
• Unsteady walking

Symptoms of more serious altitude sickness include a headache which does not respond to pain relief medication, and shortness of breath that continues while resting. Symptoms usually develop during the first 36 hours of being at high altitude.

Symptoms of cerebral oedema, which can be fatal due to fluid in the brain, include irrational behaviour, confusion and a staggering gait. Patients need to be evacuated to a lower altitude immediately. They should not return to a higher altitude until they have a medical examination.

The symptoms of pulmonary oedema, which causes fluid in the lungs, include breathlessness while resting, a persistent cough and an unusual chesty sound. Patients with this condition need immediate evacuation and medical attention.

Certain normal bodily changes happen in most people who travel to high altitude. These include:

• Breathlessness during movement
• Hyperventilation (breathing fast)
• Increase in urination
• Awakening during the night
• Strange dreams

What can be done?

The first rule with altitude sickness is not to ascend any further because this could lead to cerebral oedema or pulmonary oedema.

A climber should stay at the same altitude until they have recovered and aclimatised to the new altitude. Descending the mountain will also aid recovery. Descend if you have not recovered in one day.

Pain relief such as aspirin and paracetamol can be used to ease the headache, and drugs used for travel sickness such as prochlorperazine (Stemetil) can help relieve nausea and dizziness.

The drug acetazolamide (Diamox), which is used to treat fluid retention and makes you urinate, can be used for the treatment of minor altitude sickness. However, it does have side effects includingnausea.

The use of an oxygen mask can also be helpful.

Portable hyperbaric chambers can also be taken on an expedition. Although they cost thousands of dollars, they can also be rented, and can be life savers.

How can it be prevented?

Gaining height slowly while taking time to adjust to new altitudes is the best way to avoid illness.

At altitudes above 3000 metres your sleeping height should not rise above 300 metres a night, and every 1000 metres you should spend two nights at the same height.

Other measures to help prevent altitude sickness include keeping warm and drinking plenty of water because the body needs more water at higher altitudes. Be sure to treat or boil water before drinking it.

Make sure you eat enough even if you don't feel like it. A diet high in complex carbohydrates is generally believed to be the best food for high altitudes.

Do no over do it and become exhausted, and make sure you sleep well.

The drug acetazolamide (Diamox) can also be taken prior to ascent to help avoid altitude sickness.

Getting help

Your doctor, or local travel clinic will be able to help.

Awareness and understanding of the condition before travelling is important.