A Guide for Geologists Working at High Altitude

Geologists working at high altitude (>2,500 m, or 8,200 ft) are susceptible to altitude sickness or acute mountain sickness (AMS; mal de altura, mal de montaña, soroche, or puna in Spanish), a condition resulting from inadequate time for physiological acclimatization to lower ambient oxygen availability at reduced barometric pressure, which is driven by hypobaric hypoxia. This article outlines the symptoms, causes, prevention, and treatment of AMS, a condition triggered by exposure to high altitude without adequate acclimatization. There are three degrees of AMS—mild, moderate, and severe. Many people feel mild AMS when reaching high altitude but most acclimatize rapidly. Those with moderate AMS feel debilitated and usually require descending to low altitude to feel better. Severe AMS includes life-threatening complications involving high-altitude pulmonary edema (HAPE), an accumulation of fluid in the lungs causing shortness of breath, cough, and hypoxia, and/or high-altitude cerebral edema (HACE), the swelling of the brain leading to ataxia, confusion, and altered consciousness. Both HAPE and HACE are medical emergencies that require immediate descent and, if available, oxygen therapy and pharmacologic support. The primary cause of AMS is hypobaric hypoxia—a partial reduction in the pressure of oxygen due to decreased atmospheric pressure at altitude. The risk increases with rapid ascent, which does not allow sufficient time for the body to initiate acclimatization mechanisms such as increased ventilation and red blood cell production.