What is it?
Acute Mountain Sickness (sometimes known as altitude sickness) is caused by the lack of oxygen at high altitudes. Symptoms start usually above 2700m. Early symptoms include headaches, nausea, breathlessness, palpitations (rapid heartbeats), loss of appetite and reduced ability to exercise. Sleep can also be affected, waking frequently through the night due to ‘periodic’ breathing. Complications can develop, especially with rapid ascent to high altitude, and some may experience severe breathing difficulties. This more severe form is called high altitude pulmonary oedema (HAPE). High altitude cerebral oedema (HACE) is characterised by lack of coordination, confusion, severe headaches and even loss of consciousness. Although uncommon, both HAPE and HACE are potentially fatal.
There is no reliable way of predicting who will suffer from altitude sickness. Surprisingly increased age, lack of fitness and illnesses such as asthma 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 had no problems at high altitude previously does not guarantee that you will be symptom free next time. Some people with chronic illnesses can safely travel to high altitudes, but some diseases make high altitude travel dangerous.
The best way to avoid altitude sickness is to ascend slowly, taking several days to reach the intended destination. This allows the body time to get used to the decreasing supply of oxygen available at high altitude and is a process called acclimatization. At high altitudes it can take three to five days for your body to acclimatize before you should ascend further. If it is not possible to acclimatize — for example, if you are taking a short flight from sea-level to 3000 meters or more — acclimatization can be helped by taking the medicine acetazolamide, which helps by increasing a person’s breathing rate. This will reduce the risk of altitude sickness, but won’t guarantee to prevent it. If suffering from altitude related symptoms, it is always advisable to descend.
It is important to stay hydrated when at high altitude. Dehydration worsens altitude sickness. Much water is lost through breathing in cold, high altitudes, and also through sweat, especially when undergoing activities such as skiing or trekking. Avoiding strenuous activity in the first 24 hours at high altitude also helps to reduce the symptoms of AMS. Alcohol and sleeping pills slow down the acclimatization process and should be avoided. Alcohol also causes dehydration and worsens AMS.