altitude sickness

Article

July 5, 2022

Altitude sickness (also mountain sickness) is a syndrome in people who go to great heights without physiological adaptation to the reduced oxygen concentration in the breathing air. Another name is D'Acosta disease (after José de Acosta). The altitude at which the first symptoms appear varies from person to person and is strongly dependent on your constitution. Altitude sickness can very rarely occur between 2000 and 2500 m. The main symptoms are headaches, and there is often loss of appetite, nausea, vomiting, tiredness, weakness, shortness of breath, dizziness, tachycardia, drowsiness to the point of apathy, tinnitus and sleep disorders. Altitude sickness can turn into acute and life-threatening high-altitude cerebral edema (HACE), and high-altitude pulmonary edema (HAPE), which is also life-threatening, can develop.

Affected

Climbers

The severity and frequency of altitude sickness in mountaineers depends primarily on the altitude reached and the speed of the ascent. In unacclimatized mountaineers, 10 to 25 percent show signs of altitude sickness after climbing to 2500 meters, but these are usually mild and do not limit activity. However, 50 to 85 percent of mountaineers at an altitude of 4500 to 5500 meters are affected by insufficient acclimatization. Altitude sickness can be significantly more severe and prevent further ascent. In addition to the altitude reached, other strong risk factors for the occurrence of altitude sickness are an ascent of more than 625 meters per day from 2000 meters and a lack of previous acclimatization with less than five days above 3000 meters in the previous two months. Women are more commonly affected, as are younger people under the age of 46 and people who suffer from migraines. A lack of fitness is not a risk factor for altitude sickness.

Residents of high altitudes

In the Andes, where numerous large cities such as El Alto, La Paz, Cuzco or Quito are at an altitude of 3000 to over 4000 meters, altitude sickness, called "Soroche", is a constant problem for many locals and travelers alike. Tibetans have a genetically increased respiratory rate and increased blood flow, so that they - in contrast to the indigenous peoples of South America - do not get sick as often. Other peoples in the Himalayan region, such as the Sherpa, are also known to have a significantly reduced genetic tendency to mountain sickness, as their blood plasma production is increased. The Han Chinese are known to suffer from subacute mountain sickness in children born at high altitudes. A similar syndrome has been described in soldiers stationed for several months at altitudes above 6000 m. Chronic altitude sickness (Monge disease after its first describer Carlos Monge Medrano, 1925) affects long-term residents of high altitudes; here there is also polycythemia, pulmonary embolism and symptoms similar to Pickwick syndrome.

Causes and history

The reason for this is that the air pressure drops with increasing altitude and with it the oxygen partial pressure. In addition to the already reduced oxygen uptake, the low oxygen partial pressure leads to a narrowing of the blood vessels in the lungs (pulmonary vasoconstriction; see Euler-Liljestrand mechanism) and thus to a further drop in the oxygen content in the blood. The body is undersupplied with oxygen (hypoxia). The body's own respiratory regulation does not counteract this, as it primarily reacts to the carbon dioxide content, the blood's strongest respiratory drive. However, this does not increase with decreasing air pressure. High-altitude pulmonary edema and high-altitude cerebral edema can occur as further complications. Due to the prevailing lack of oxygen, reflex hyperventilation occurs, which is caused by increased exhalation