Altitude sickness

From ArticleWorld

Altitude sickness, also called Acute Mountain Sickness (AMS), results from the inability of the body to function with the lack of oxygen at altitudes higher than 2,400-3,000 m, most often because of too-fast ascent. If acclimatization is not managed properly, altitude sickness can either cause mild to severe discomfort, and in extereme cases lead to serious pulmonary or cerebral damage, or even death. Susceptibility to mountain sickness is often said to have very little to do with a person's fitness. The physiological causes of more serious manifestations of AMS are undetermined.

Acclimatization

While it is recognised that some people feel the effects of altitude as low as 1,500m, generally, most people can ascend up to 3,000 m with little or no discomfort. Above this, however, the standard practice for people who normally live at low altitude is 'Climb higher, sleep lower', and the recommended gain in altitude is no more than 300 m per day. Climbing higher starts the process of acclimatization, which is simply the body getting used to functioning with less oxygen. Oxygen saturation in the blood can drop by as much 25% at very high altitude such as mountaineers often find themselves in.

Symptoms

The most common symptom at altitude is a dull, heavy headache. This in itself is not cause for alarm, and indicates merely that the body is actively adjusting to the change. Discomfort worsens when the headache is accompanied by nausea, fatigue, malaise, lightheadedness and insomnia. At this stage it is sensible to remain at the same altitude, or even descend for a night. Descent is essential if a person is disoriented, vomiting often, or coughing up frothy liquid.

At its worst, altitude sickness can turn into edema, or the accumulation of fluid in the body. High Altitude Pulomonary Edema (HAPE) is fluid retention in lungs, causing hacking, deep coughs without phlegm, rales, acute nausea and fatigue, dyspnea, and even fluid retention in the kidneys. Potentially very painful and dangerous, HAPE can be improved by bringing the person down to a lower altitude, preferably below 3,000 m.

High Altitude Cerebral Edema is less common, affect 1%, or half those who get HAPE, but much more dangerous, and often fatal. HACE is described in accounts of Himalayan climbing, as well as undertakings such as David Breashears' The Death Zone. Symptoms include serious confusion, loss of coordination and reflexes, impaired thought, bowel dysfunction, paralysis, and judgment-threatening fatigue and visual impairment. Evacuation to lower altiitude nis the only way to save people with HACE, ideally below 2,700 m, though every hundred metres counts.

Therapeutic measures

While proper acclimatization and descent on developing symptoms are the only sure-fire ways to deal with AMS, trekkers, climbers, and travellers to places like Lhasa, La Paz, and Everest base camp sometimes take acetazolamide, commonly called Diamox, to relieve symptoms on the milder end of the AMS spectrum, and speed up acclimatization once the symptoms appear. Of great therapeutic value are bottled oxygen, and Gamow bags, which can reduce the effective altitude for those inside them by as much as 1,500 m, and bring immediate relief from symptoms. People suffering from HAPE and HACE are administered dexamethasone, though descent and immediate medical treatment of symptoms is the only real solution.