High altitude may be easily defined by three categories: High Altitude, Very High Altitude and Extreme Altitude. Each of these are defined below.
High Altitude: High altitude may be defined as elevations between 5000 and 11,500 feet. Given sufficient time most climbers will adapt to these types of elevations.
Very High Altitude: Though more than 10 million people throughout the world live at altitudes that range between 11,500 and 18,000 feet, the rest of us do not. As a result a variety of individual factors come into play when traveling to such an altitude. A climber's fitness and his age are both huge factors at such altitudes. Surprisingly, younger climbers tend to have more problems at altitude than older climbers.
Extreme Altitude: Elevations that exceed 18,000 feet are considered extreme. Performance at such high altitudes declines dramatically.
Death Zone: The words, "death zone" say it all. You probably should not spend too much time above 26,000 feet if you want to stay alive.
These definitions really don't mean much. They're simply an academic way to understand altitude. Your body will respond to altitude changes at every elevation no matter what the name of the altitude is. Some people will do well up high at extreme altitudes and some won't.
Thinner air and adaptation to a higher altitude results in a number of physiological effects. The first thing you'll notice is heavier breathing and diuresis (you'll need to pee a lot). As you notice this a million different things are going on in your body as you climb to higher altitudes. These changes include the following from medicinenet.com:
If your body is not adapting properly you may actually get sick. If the sickness appears to be getting worse, the best thing to do is to descend to a lower altitude. There are three types of altitude related illnesses to watch out for. Two of the three can be fatal, so it is incredibly important to monitor yourself and your team-members. The altitude illnesses are as follows:
- The depth of respiration increases;
- The pressure in the pulmonary arteries increases, forcing blood into portions of the lung which are normally not used at sea level;
- We make more red blood cells to carry oxygen;
- We make more of a specific substance (called 2,4-DPG)that facilitates the release of oxygen from hemoglobin to the body tissues.
Acclimatization generally takes 1 to 3 days at a given altitude. For example, if a person hikes to 10,000 feet (3,048 meters) and spends several days at that altitude, their body acclimatizes to 10,000 feet (3,048 meters). If the person then climbs to 12,000 feet (3,658 meters), the body needs to acclimatize once again and it takes another 1 to 3 days.
Acute Mountain Sickness (AMS): This is a common response to a rapid change in elevation. Symptoms include headaches and nausea. Usually this will go away after you hydrate and spend some time at a given altitude.
High Altitude Pulmonary Edema (HAPE): This is a life-threatening pulmonary edema that results from an increased blood flow through the lungs. Symptoms include wet sounds in the lungs, dizzyness, and sometimes even bloody sputum. Symptoms develop very quickly and the response -- to get the victim down to a lower altitude -- must take place just as quickly.
High Altitude Cerebral Edema (HACE): This is a life-threatening swelling of the brain. Symptoms include poorly functioning mental abilities (i.e. confusion, fatigue and weird behavior) and severe ataxia (dizzyness). As with HAPE, it is extremely important to immediately descend with the victim.
In this brief discussion we were not able to cover every type of treatment for different altitude related problems and we didn't even touch on altitude drugs. To dip deeper into the world of high altitude mountaineering and altitude physiology you might enjoy Altitude Illness: Prevention and Treatment by Stephen Bezruchka and Mountain Sickness Prevention Recognition and Treatment by Dr. Peter Hackett.
--Jason D. Martin