Altitude and Travel

Acute mountain sickness (AMS) is a health risk that is a concern for any traveller adventuring at high altitudes.

High altitude or acute mountain sickness

Acute mountain sickness

Acute mountain sickness (AMS) is common among travellers visiting destinations 2,500 metres above sea level or higher. Around 50% of these travellers are affected by AMS.

Why? The higher the altitude, the less oxygen there is in the air. The 'thinner' the air becomes, the harder it is for the human body to function normally. This is especially true if the ascent has been rapid.

As a result, breathing can become deeper and more rapid, the pulse quickens, and the ankles and hands may swell.

Mild symptoms of AMS

Some, or all, of the range of AMS symptoms can appear within several hours of arrival, or up to three days later. These may include:

  • shortness of breath during exertion
  • headache
  • tiredness
  • loss of appetite
  • dizziness
  • nausea/vomiting (common in children)
  • sleeping difficulties.

For most people, these symptoms ease completely when they acclimatise by spending several days at the same altitude. If symptoms do not abate, descending to a lower altitude generally makes symptoms disappear.

It is important not to go higher if you have ANY symptoms of altitude sickness.

Severe symptoms of AMS

For most people, these symptoms ease completely when they acclimatise by spending several days at the same altitude. If symptoms do not abate, descending to a lower altitude generally makes symptoms disappear.

It is important not to go higher if you have ANY symptoms of altitude sickness.

  • extreme fatigue
  • drowsiness
  • confusion
  • loss of coordination

HAPE affects the lungs. Difficulties with breathing lead to low oxygen levels in the body, followed by respiratory failure and death. Its symptoms include:

  • shortness of breath 
  • weakness
  • cough.
Prevention

The key to preventing AMS is gradual acclimatisation. Ascend slowly. The Wilderness Medical Society recommends acclimatising for a minimum of 2 to 3 nights at 2450–2750 metres before proceeding to higher elevations. They recommend avoiding ascent to a sleeping elevation of 2,750 metres in a single day and not ascending at a rate greater than 500 metres per night once above 3,000 metres. You should also allow an extra night to acclimatise for every ≈1,000 metres of sleeping elevation gain.

 It is also advisable to:

  •  Sleep at a lower altitude than the height reached during that day’s ascent.
  • Eat light, high-carb meals for extra energy.
  • Avoid alcohol. It increases urine output and causes dehydration.
  • Take medication as directed by your travel doctor.
  • Drink additional fluids. Mountain air is cold and dry, and moisture is lost with every breath. Drink enough water and safe fluids to ensure a strong flow of clear urine. If signs of dehydration are present, take extra doses of oral rehydration solution or water.
  • Avoid sedatives.

Rapid ascent is the main contributing factor in AMS at altitudes of 2,500 metres or above. If trekking or climbing above 4,500 metres, the ascent should be well planned. Climbers should have access to treatment medications for both HACE and HAPE.