High Altitude Pulmonary Edema

High altitude pulmonary edema (HAPE) is one of a number of related altitude sicknesses that can affect persons exercising at altitudes they are not accustomed to. HAPE will typically occur at elevations greater than 6,500 ft (2,000 m). The common feature in all types of altitude sicknesses is the onset of hypoxia, a deficiency in the amount of oxygen reaching the body's, particularly the brain, where there is otherwise an adequate supply of blood.

At high altitudes, the amount of oxygen in the air available to the cardiorespiratory system is less than the amount available at sea level, as the reduced

effect of gravity makes the air less dense. There is less oxygen available to enter the body through the lungs; at an elevation of 10,000 ft (3,100 m), the body will have approximately 90% of its normal oxygen level at sea level. HAPE occurs when the body has not been provided an appropriate opportunity to adjust its internal mechanisms to the reduced oxygen environment. This process, known as ventilatory acclimatization, requires approximately four days in which to occur. An important aspect of this acclimatization process is the body's increased production of both erythropoietin (EPO), the hormone that stimulates the production of oxygen transporting red blood cells, and hemoglobin, the oxygen carrying component of the red blood cells.

HAPE occurs in three separate, but related, high altitude circumstances-where the subject has made a rapid ascent to an altitude above 6,500 ft; where the subject has engaged in vigorous exercise at high altitude; where the subject has been exposed to very cold weather. In all circumstances, the body is not able to direct sufficient amounts of oxygen into the body. The onset of HAPE is also affected by the genetic makeup of the individual, as some persons are more susceptible to the onset of HAPE.

The symptoms of HAPE do not usually present themselves until the subject has been at the unaccustomed altitude for 48 hours or more. The most prominent symptoms are a decreased tolerance to exercise and low blood pressure. The injured person may also experience a retinal hemorrhage.

The primary treatment for HAPE is to transport the subject to a lower altitude or to introduce oxygen into the subject's respiratory system. If untreated HAPE can be a fatal condition. There are many ski resorts and lodges through out both Europe and the mountainous districts of North America that at elevations above the level where HAPE may present a risk. A study of Colorado resorts determined an incidence of HAPE of roughly one case per 10,000 skiers per day.

SEE ALSO Cardiopulmonary function; Cardiovascular system; High altitude effects on sport performance.