AMS is common at high altitude. At elevations over 10,000 feet (3,048 meters), 75% of people will have mild symptoms. The occurrence of AMS is dependent upon the elevation, the rate of ascent, and individual susceptibility. The symptoms of mild AMS are headache, dizziness, fatigue, shortness of breath, loss of appetite, nausea, disturbed sleep, and a general feeling of malaise.
Moderate AMS
Moderate AMS includes severe headache that is not relieved with medication, nausea, and vomiting, increasing weakness and fatigue, shortness of breath, and decreased coordination (ataxia). Normal activity is difficult at best. A good test for moderate AMS is to have the person "walk a straight line" heel to toe. A person with ataxia will be unable to walk the straight line. This is a clear indication that immediate descent is required. It is important to get the person to descend before the ataxia reaches a point where they cannot walk on their own at which point a litter evacuation would be required.
Severe AMS
Symptoms of Severe AMS include shortness of breath at rest, inability to walk, decreasing mental status, and fluid build-up in the lungs. Severe AMS requires immediate descent to lower altitudes (2,000 - 4,000 feet).
There are two other forms of altitude illness, High Altitude Pulmonary Edema (HAPE), and High Altitude Cerebral Edema (HACE). When these occur, it is usually with people going too high too fast or going very high and staying there. The lack of oxygen results in leakage of fluid through the capillary walls into either the lungs or the brain.
Diamox
What is High Altitude?
Acute Mountain Sickness
High Altitude Pulmonary Edema (HAPE)
High Altitude Cerebral Edema (HACE)
