Severe altitude sickness can lead to two very serious conditions: cerebral oedema and pulmonary oedema.
These conditions are rare, but can occur if a person ascends to a very high altitude too quickly and stays there.
High altitude cerebral oedema
High altitude cerebral oedema (HACO) occurs when a lack of oxygen causes fluid to leak through the capillary walls and into the brain, causing the brain tissue to swell. Capillaries are tiny blood vessels that surround major organs, such as the brain, heart and lungs.
The symptoms of HACO include:
- headache
- weakness
- disorientation
- loss of co-ordination
- memory loss
- hallucinations and an inability to distinguish between reality and imagination
- loss of consciousness
- coma
HACO can occur if a person ascends rapidly to high altitude, or stays at a very high altitude for a week or longer. If it is not treated immediately, it is likely that HACO will lead to death. To prevent this, an immediate descent of at least 600m (2,000 feet) is necessary.
The steroid medication dexamethasone can be used to treat HACO. Oxygen should be given if available. However, if possible, someone with the condition should be transferred to hospital as soon as possible to receive follow-up treatment.
In practice, this may involve transfer by emergency helicopter, although in many parts of the world no formal rescue services exist, and it should also be remembered that at extreme altitudes (for example on the upper slopes of 8,000m peaks), helicopters may not be able to operate.
High altitude pulmonary oedema
High altitude pulmonary oedema (HAPO) occurs when fluid builds up in the lungs. The fluid prevents oxygen from being transferred from the lungs into the bloodstream. As the condition gets worse, the amount of oxygen in the blood decreases, which causes the following symptoms:
- cyanosis (a blue tinge to the skin)
- severe breathing difficulties (even when resting)
- tightness in the chest (caused by the pulmonary artery narrowing)
- a persistent cough, bringing up white frothy liquid (sputum)
- extreme tiredness and weakness
- confusion and disorientation
- irrational behaviour
Eventually, it will lead to death.
The symptoms of confusion and irrational behaviour are due to a lack of oxygen to the brain. To prevent death, someone with HAPO should descend immediately by at least 600m (2,000 feet).
Nifedipine is a medication that can be used to treat HAPO. However, as with HACO, someone with the symptoms of HAPO should be transferred to hospital as soon as possible for follow-up treatment.
The HAPE database
If you or someone you know has had HACO or HAPO, you can register with the International HAPE Database. The database has been set up to assist with research into these two very serious health conditions.
