Climbing Facts and Health Risks
Acclimatization
Acclimatization is the process of the body adjusting to the decreased availability of oxygen at high altitudes. It is a slow process, taking place over a period of days to weeks.
High altitude is broken down as:
- High Altitude: 1500 - 3500 m (5000 - 11500 ft)
- Very High Altitude: 3500 - 5500 m (11500 - 18000 ft)
- Extreme Altitude: above 5500 m (18000 ft + )
Certain normal physiologic changes occur in every person who goes to altitude:
- Hyperventilation (breathing faster, deeper, or both);
- Shortness of breath during exertion;
- Changed breathing pattern at night;
- Awakening frequently at night;
- Increased urination.
As one ascends through the atmosphere, barometric pressure decreases, so you must work harder to obtain oxygen, by breathing faster and deeper.
Acclimatizing safely.
With altitude, there are certain health risks that can occur. Climbers should be vigilant of any signs of these conditions in themselves or their fellow climbers.
Acute Mountain Sickness (AMS)
AMS is a result of your body not being acclimatized to its current altitude.
As you ascend, your body acclimatizes to the decreasing oxygen. But if you ascend more quickly than your body can adapt, you can get altitude sickness. The exact mechanisms of AMS are not completely understood. A person likely has AMS when a headache plus any one or more of the following symptoms is present after a recent ascent above 2500 meters (8000 feet):
- Loss of appetite, nausea, or vomiting;
- Fatigue or weakness;
- Dizziness or light-headedness;
- Difficulty sleeping.
All of these symptoms may vary from mild to severe. AMS has been likened to a bad hangover, or worse. However, because the symptoms of mild AMS can be somewhat vague, a useful rule-of-thumb is: if you feel unwell at altitude, it is altitude sickness unless there is another obvious explanation.
Anyone who goes to altitude can get AMS. It is primarily related to individual physiology and the rate of ascent; there is no significant effect of age, gender, physical fitness, or previous altitude experience. Some people acclimatize quickly, and can ascend rapidly; others acclimatize slowly and have trouble staying well even on a slow ascent. There are factors that we don't understand; the same person may get AMS on one trip and not another despite an identical ascent itinerary.
High Altitude Cerebral Edema (HACE)
AMS is a spectrum of illness, from mild to life-threatening. At the "severely ill" end of this spectrum is High Altitude Cerebral Edema, when the brain swells and ceases to function properly. HACE can progress rapidly, and can be fatal in a matter of a few hours to one or two days.
Symptoms of HACE are:
- reduced ability to think clearly;
- lethargy;
- loss of co-ordination and staggering walk.
Immediate descent is the best treatment for HACE.
High Altitude Pulmonary Edema (HAPE).
Another form of severe altitude illness is High Altitude Pulmonary Edema, or fluid in the lungs. Signs and symptoms of HAPE include any of the following:
- extreme fatigue;
- breathlessness at rest;
- cough, possibly productive of frothy or pink sputum;
- gurgling or rattling breaths;
- chest tightness, fullness, or congestion;
- blue or grey lips or fingernails.
The treatment for HAPE is the same as for HACE: immediate descent.
Preventing Acute Mountain Sickness
The key to avoiding AMS is a gradual ascent that gives your body time to acclimatize. People acclimatize at different rates, so no absolute statements are possible, but in general, the following recommendations will keep most people from getting AMS:
- If possible, you should spend at least one night at an intermediate elevation below 3000 meters.
- At altitudes above 3000 meters (10,000 feet), your sleeping elevation should not increase more than 300-500 meters (1000-1500 feet) per night.
- Every 1000 meters (3000 feet) you should spend a second night at the same elevation.
Remember, it's how high you sleep each night that really counts; climbers have understood this for years, and have a maxim "climb high, sleep low". The day hikes to higher elevations that you take on your "rest days" (when you spend a second night at the same altitude) help your acclimatization by exposing you to higher elevations, then you return to a lower (safer) elevation to sleep. This second night also ensures that you are fully acclimatized and ready for further ascent.
