HEALTH & SAFETY

High altitude has a relative meaning. However, for our purposes we have adopted the following measurements.

High    2,500 to 3,500 meters or 8,202 to 11,482 ft
Very High    3,500 to 5,500 meters or 11,482 to 18,044 ft
Extremely High   5,500+ meters or 18,044+ ft

People react differently to high elevation. In spite of significant research on the subject, the question of exactly who performs well or doesn’t perform well at altitude is evasive. There is agreement, however, that performance is largely dictated by personal physiology and experience at high elevation. The high alpine environment is a spectacular place to visit, but humans are generally unable to survive above approximately 17,000 ft. for any significant length of time due to a reduction in available oxygen. As elevation increases, available oxygen decreases. Consequently, a climber advancing up a mountain will experience greater and more acute fatigue as elevation increases. A climber at 17,000 ft. may survive for months while a climber above 23,000 ft. may survive for only hours. Remarkably, reports of people suffering from altitude at only 6,000 ft. are common in the Western United States.

Air at sea level comprises about 21% oxygen, while the barometric pressure averages about 1 bar (1000 mbar). As altitude increases, the oxygen concentration remains the same, but since the pressure falls, the number of oxygen molecules per breath is reduced. At 11,500 ft, the barometric pressure is only about 630 mbar (depending on weather), so there are roughly 40% fewer oxygen molecules per breath. In order to supply an adequate amount of oxygen to the body, breathing must increase. This extra breathing increases the amount of oxygen in the blood, but not in comparison to sea level volumes. Since the amount of oxygen required for activity is the same, the body must adjust itself to coping with less oxygen. This process is known as “acclimatization.” Failure to give your body the opportunity to undergo this process may lead to a dangerous condition known as acute mountain sickness.

Experienced high altitude mountaineers are familiar with their unique physiology and the rate at which they can advance up a mountain safely using the acclimitization process. Based on experience and strong personal awareness, these mountaineers understand how their bodies react to altitude and their limitations. Experienced mountaineers frequently have their acclimitization schedules and performance factors down to science. For example, a high performance mountaineer understands how much altitude they can achieve over what mileage and in what period of time. Further, the individual understands what amount of food and water must be consumed from base-summit-base to remain healthy.

It takes many climbers years of experience to understand their physiology and acclimitization schedule. To achieve a full appreciation of the acclimitization process, mountaineers must also be familiar with the conditions that may result from high altitude exposure described below.

Acute Mountain Sickness

Acute mountain sickness (AMS) is common. At elevations over 10,000 ft., three quarters of people can expect to suffer mild symptoms. The occurrence of altitude sickness is dependent upon several factors, including elevation, rate of ascent and the individual’s susceptibility. Many people experience mild altitude sickness during a normal acclimatization process.
Symptoms usually start 12-24 hours after arrival at altitude and begin to decrease in severity after the second or third day. Symptoms of mild AMS may include a headache, dizziness, fatigue, shortness of breath, loss of appetite, nausea, disturbed sleep and a general feeling of malaise. Symptoms may be more severe at night when rate of respiration decreases.
Mild altitude sickness does not interfere with normal activity and symptoms generally subside within 72 hours as the body acclimatizes. If symptoms are mild, ascent can normally continue at a moderate rate.
Altitude sickness is considered to be a neurological problem caused by changes in the central nervous system. The only cure is acclimatization or descending. Symptoms of mild AMS can be alleviated with analgesics, but it is important to note that masking the symptoms is not treating the problem. Consequently, introduction of medication may be masking the symptoms of a more serious condition.

Moderate AMS

Moderate AMS symptoms may include a severe headache that cannot be relieved with medication, nausea and vomiting, increasing weakness and fatigue, shortness of breath and decreased coordination (ataxia). Normal activity is difficult, although the person may still be able to walk on their own. Descending 500-1,000 ft. for twenty-four hours or more may result in improvement. Individuals suffering from Moderate AMS should remain at lower altitude until symptoms have resolved. Ataxia may be the clearest indication that immediate descent is required. It is important that the individual descend before the ataxia impairs the ability to walk independently.

High Altitude Pulmonary Edema (HAPE)

HAPE results from fluid build-up in the lungs. The lack of oxygen results in fluid leakage through the capillary walls and into the lungs, preventing oxygen exchange. As the condition becomes more severe, the level of oxygen in the bloodstream decreases, potentially leading to cyanosis, impaired brain function and eventual death. Symptoms may include a shortness of breath at rest & tightness in the chest, fatigue & weakness, feeling of impending suffocation at night, persistent cough producing white, watery, or frothy fluid, confusion and irrational behavior. HAPE requires immediate descent of 3,000 ft. or more. Climbers suffering from HAPE generally require evacuation for advanced care and treatment.

High Altitude Cerebral Edema (HACE)

Also a serious condition requiring immediate action, HACE is the result oxygen deprivation leading to a swelling of the brain tissue from fluid leakage. Symptoms may include headache, ataxia, weakness, decreasing levels of consciousness, disorientation, loss of memory, hallucination, combative behavior, comatose and eventual death. HACE requires immediate descent of 3,000 ft. or more. Climbers suffering from HACE generally require evacuation for advanced care and treatment.