Altitude sickness, often called high-altitude sickness, is an illness caused by lack of oxygen in the blood and body tissues at high altitude. People who normally live at low altitudes may find that they have problems adjusting to the high altitudes of many mountain regions. Air pressure decreases with altitude, thereby forcing a person’s body to function with lower levels of oxygen than those found at or near sea level.
The primary cause of high-altitude sickness is hypoxia (insufficient levels of oxygen in the blood or body tissue). Symptoms of high-altitude sickness usually occur at altitudes over 7,000 feet (2,100 meters) above sea level. Physicians recognize three forms of altitude sickness: (1) acute mountain sickness (AMS), (2) high-altitude cerebral edema (HACE), and (3) high-altitude pulmonary edema (HAPE). Medical experts do not fully understand the cause of AMS, but they believe it is related to swelling that occurs in the brain at high altitudes. Common symptoms of AMS include nausea, poor sleep, headache, and drowsiness. With HACE, the symptoms are similar to those of AMS but are more severe and also include loss of balance and changes in mental condition. Individuals suffering from HAPE experience a build-up of fluid in the lungs. They typically have a cough, gurgling breaths, chest congestion, and difficulty breathing. Most deaths from high-altitude sickness can be attributed to HAPE.
Treatment of altitude sickness is best accomplished by descent to a lower elevation. A person with symptoms of altitude sickness should descend to a lower altitude immediately. Physicians may also administer supplemental oxygen and medications if necessary.
There are several drugs that can help prevent and treat altitude sickness. One drug, called acetazolamide, is effective in preventing and treating AMS. The drug increases breathing rate and thus raises the amount of oxygen in the blood. Another drug, called dexamethasone, reduces brain swelling and is commonly used to treat HACE. Supplemental oxygen is the best treatment for HAPE, but physicians may also use a drug called nifedipine. This drug acts to halt fluid build-up in the lungs.
Another method used to treat altitude sickness involves the use of a portable chamber made from lightweight fabric. One such device, called a Gamow bag, is big enough to hold an adult, sealed inside the zippered bag. The air pressure inside the bag is then raised using a portable air pump. Once inflated, the interior environment of the bag simulates the air pressure at lower elevation and thereby relieves the symptoms of altitude sickness.
A gradual ascent to high altitude that allows the body a chance to adjust to hypoxia is the most effective way to prevent altitude sickness. Physicians recommend that once people climb above an altitude of 8,200 feet (2,500 meters), they should take an extra day of rest for every increase of 2,000 feet (600 meters) to 4,000 feet (1,200 meters) ascent above this altitude.
See also Anoxia .
