Although rare, altitude sickness can also lead to potentially life-threatening conditions that affect the brain or lungs. 

High altitude cerebral oedema

High altitude cerebral oedema (HACE) occurs when a lack of oxygen causes fluid to leak through the capillary walls and into the brain, resulting in swelling of the brain tissue. Capillaries are tiny blood vessels that surround major organs, such as the brain, heart and lungs.

Symptoms of HACE can include:

• headache
• weakness
• disorientation
• loss of co-ordination
• memory loss
• hallucinations and an inability to distinguish between reality and imagination
• loss of consciousness, eventually leading to coma

HACE can occur if a person ascends to a high altitude rapidly or stays at a very high altitude for a week or longer. A person with HACE often doesn't realise the seriousness of their condition, and may insist they're all right and want to be left alone.

If HACE isn't treated immediately, it's likely it will be fatal. Immediate descent to a lower altitude is necessary to prevent this.

The steroid medication dexamethasone can be used to treat HACE. If available, oxygen should also be given. Someone with HACE should be transferred to hospital quickly to receive follow-up treatment.

See treating altitude sickness for more information.

Dexamethasone

Dexamethasone can be very useful for treating severe complications of altitude sickness, such as high altitude cerebral oedema (HACE). It is a strong steroid that reduces swelling of the brain, and is usually taken as a tablet several times a day.

The medication is particularly useful for "buying time" until it's safe to make a descent. For example, it can be used during the night to relieve symptoms when making a descent isn't possible or may be dangerous. Symptoms usually start to improve within about six hours.

Dexamethasone can cause side effects such as stomach upset, difficulty sleeping (insomnia) and mood changes.

High altitude pulmonary oedema

High altitude pulmonary oedema (HAPE) occurs when fluid builds up in the lungs. The fluid prevents oxygen being transferred from the lungs into the bloodstream.

As the condition worsens, the amount of oxygen in the blood decreases, which can cause:

• a blue tinge to the skin (cyanosis)
• severe breathing difficulties (even when resting)
• tightness in the chest
• a persistent cough, bringing up pink or white frothy liquid (sputum)
• extreme tiredness and weakness
• confusion and disorientation
• irrational behaviour

The symptoms of confusion and irrational behaviour are caused by a lack of oxygen to the brain, but can also occur in high altitude cerebral oedema. To prevent death, someone with HAPE should descend immediately to a low altitude.

Nifedipine is a medication that can be used to treat HAPE. Dexamethasone may also be useful, although further studies are needed to assess its effectiveness.

As with HACE, someone with the symptoms of HAPE should be transferred to hospital as soon as possible for follow-up treatment.

See treating altitude sickness for more information.

The HAPE database

If you or someone you know has experienced HAPE, you can register with the International HAPE Database. The database has been set up to assist with research into this very serious health condition.