Travel Reference
In-Depth Information
major risk factor. On average, one tourist a year dies in Tibet from AMS. Any traveller who
flies to where the elevation is around 3600m is likely to experience some symptoms of
AMS.
AMS is a notoriously fickle affliction and can also affect trekkers and walkers accustomed
to walking at high altitudes. It has been fatal at 3000m, although 3500m to 4500m is the
usual range.
ACCLIMATISATION
AMS is linked to low atmospheric pressure. Those who travel up to Everest Base Camp, for
instance, reach an altitude where atmospheric pressure is about half of that at sea level.
With an increase in altitude, the human body needs time to develop physiological mech-
anisms to cope with the decreased oxygen. This process of acclimatisation is still not fully
understood, but is known to involve modifications in breathing patterns and heart rate in-
duced by the autonomic nervous system, and an increase in the blood's oxygen-carrying
capabilities. These compensatory mechanisms usually take about one to three days to de-
velop at a particular altitude. You are unlikely to get AMS once you are acclimatised to a
given height, but you can still get ill when you travel higher. If the ascent is too high and too
fast, these compensatory reactions may not kick into gear fast enough.
SYMPTOMS
Mild symptoms of AMS usually develop during the first 24 hours at altitude. These will gen-
erally disappear through acclimatisation in several hours to several days.
Symptoms tend to be worse at night and include headache, dizziness, lethargy, loss of
appetite, nausea, breathlessness and irritability. Difficulty sleeping is another common
symptom, and many travellers have trouble for the first few days after arriving in Lhasa.
AMS may become more serious without warning and can be fatal. Symptoms are caused
by the accumulation of fluid in the lungs and brain, and include breathlessness at rest, a dry
irritative cough (which may progress to the production of pink, frothy sputum), severe head-
ache, lack of coordination (typically leading to a 'drunken walk'), confusion, irrational beha-
viour, vomiting and eventually unconsciousness.
The symptoms of AMS, however mild, are a warning: be sure to take them seriously!
Trekkers should keep an eye on each other as those experiencing symptoms, especially
severe symptoms, may not be in a position to recognise them. One thing to note is that
while the symptoms of mild AMS often precede those of severe AMS, this is not always the
case. Severe AMS can strike with little or no warning.
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