Altitude sickness
With increasing overseas travel and a growing interest in ‘adventure’ holidays, many people are concerned about the dangers of trekking or climbing in areas of high altitude. Altitude (or ‘mountain’) sickness is a very real problem that can have serious, and even fatal, results.
Altitude sickness is caused by the relative lack of oxygen available from the air at high altitudes, due to the difference in atmospheric pressure compared with sea level. In its mildest form, the problem can occur at heights as low as 2000 metres.
Mild cases usually involve headaches, nausea, breathlessness, palpitations and reduced ability to exercise. These symptoms will usually disappear in a few days if the person stays at the same altitude.
More serious forms happen at high altitude (usually defined as more than 3000 metres). In addition to the symptoms already mentioned, affected people may have loss of appetite and difficulty sleeping, and may wake up frequently through the night due to ‘periodic’ breathing. Periodic breathing is when a person breathes normally then stops breathing for 10-15 seconds, which wakes them up. Severe breathing difficulties, vomiting, frequent cough, lack of coordination and loss of consciousness are among the more serious symptoms and necessitate immediate descent or putting the person in a portable altitude chamber. The chamber artificially puts the person at a higher atmospheric pressure and gives the same effect as descending.
There is no way of predicting who will, or will not, suffer from altitude sickness. Surprisingly, increased age, lack of fitness and illnesses such as asthmatic conditions do not seem to make people more prone to the problem. Having had altitude sickness before does not mean that you will necessarily get it again, however, you will be more susceptible. Similarly, having been okay at altitude previously does not guarantee that you will be okay next time.
The best way to avoid mountain sickness is to ascend slowly, taking several days to get to the intended destination. If this cannot be managed — for example, on short flights from sea-level to 3000 metres or more — acclimatisation can be helped by the use of a drug called Diamox, which is started 2 or 3 days before the planned trip. Your doctor can advise if this is necessary or suitable for you.
It is important to stay hydrated when at altitude. Dehydration is a contributing factor to altitude sickness. Much water is lost in the breath in cold, high altitudes, and also by evaporation through sweat, especially when undergoing activities such as skiing or trekking.
If you are planning a trip that involves ascending to high altitudes in a relatively short time, discuss potential problems with your doctor.
Last Reviewed: 13 October 2004
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