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What is altitude sickness?

Altitude sickness is a condition that occurs when your body doesn't adjust to the low oxygen or 'thinner' air at high altitudes. It usually occurs when you travel to a high altitude too quickly, without allowing your body to acclimatise to the lack of oxygen. It is also known as acute mountain sickness.

Altitude sickness is usually mild or moderate. However, serious cases can occur, causing fluid in the lungs or brain. If not treated immediately, these serious cases can be fatal.

What causes altitude sickness?

Oxygen levels in the air begin to decrease when you reach 1,500 metres above sea level. This means that getting enough oxygen for your body can be very difficult. Your body has to breathe faster and pump blood faster to continue providing sufficient oxygen for your organs. When this process occurs too quickly and without adequate rest, it can lead to altitude sickness.

Mild altitude sickness is common from around 2,500 metres (8,000 feet) and up. Severe altitude sickness usually occurs at around 3,600 metres (12,000 feet) and up. The severity of the illness mostly depends on how fast you ascend and what height you reach.

What are the symptoms of altitude sickness?

Symptoms of altitude sickness include headache, loss of appetite, nausea, dizziness, weakness, difficulty sleeping, and shortness of breath. Symptoms usually develop between 6 and 24 hours after reaching a high altitude. As your body gets used to the high altitude, the symptoms improve. If they don't improve during within 48 hours, you should descend to a lower altitude immediately, as you may be developing complications.

When altitude sickness becomes serious, it can develop into two life-threatening conditions affecting your lungs and brain: High Altitude Pulmonary Oedema (HAPE) and High Altitude Cerebral Oedema (HACE).

HAPE is caused by fluid leaking into the lungs and preventing oxygen from entering the bloodstream. Symptoms include severe breathing problems, extreme fatigue, chest tightness, blue skin, disorientation, irrationality, and a persistent cough that produces frothy liquid.

HACE is caused by fluid leaking through the capillaries that surround the brain and making the brain swell. Symptoms include loss of coordination, hallucinations, disorientation, weakness, headaches, and loss of consciousness.

Both HACE and HAPE are medical emergencies and can be fatal if not immediately treated. If you have any symptoms of these conditions, you must descend to a lower altitude and seek medical treatment.

How can I prevent altitude sickness?

Allowing yourself adequate time to acclimatise to the higher altitude is the best way to prevent altitude sickness. Acclimatising means resting at each new altitude. If you are going to a very high altitude, you may need to rest and spend a night at several points on the journey. Avoiding strenuous activity until at least 24 hours after arriving at your highest altitude, as well as drinking lots of water, can also minimise the risk of altitude sickness.

What medication treats altitude sickness?

121Doc provides Diamox, a medication used to treat and prevent altitude sickness. Its active ingredient is acetazolamide, which is thought to correct the chemical imbalance in your blood that altitude sickness can cause.

In the UK, Diamox is not licensed to treat altitude sickness, but it is regularly prescribed 'off-label'' for this purpose. This means that the medicine has not undergone clinical trials for this purpose, but is used as an effective and safe treatment for the condition.

Diamox should be taken a few days before ascending to ensure effectiveness. Though it is effective in reducing altitude sickness, Diamox is not a replacement for following the correct acclimatisation methods.

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