Rapid ascent to the summit of Mount Everest ft could cause loss of consciousness and death. Yet climbers ascending.
This peak over a period of weeks, without supplemental O, have experienced only minor medical problems. The process by which humans gradually adjust to hypoxia, enhance performance, and increase their chances of survival is known as altitude acclimatization. Successful acclimatization also improves sleep and protects against altitude illnesses.
Englishman Doug Scottwho has successfully conquered Mount Everest, Mount McKinley, and several of the world's tallest peakscommented on the importance of acclimatization.
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No, I don't acclimatize quickly, but once I have acclimatized, I seem to get along well. I have to allow myself a good three weeks before I feel like climbing reasonably, before I feel anything like climbing.. I don't know anybody who won't benefit from three weeks of acclimatizing. His estimate of the time required to acclimatize has been supported by several experts.
Numerous physiologic adaptations occur in humans during chronic exposure to a hypobaric-hypoxic environment such as Mount Everest. Many of these have been clarified in studies that transported lowland visitors to high- or extreme-altitude locations.
During several weeks at altitude, the gradient of between the alveoli and the blood increases during exercise, thereby increasing the arterial content and reducing hypoxia.
Chemical receptors in the carotid arteries of the neck become more sensitive to hypoxia and stimulate greater ventilation, thereby increasing levels in the blood. This response is vital; without it, the brain would not sense the danger of low levels in arterial blood. Over many weeks and months, however, this adaptation is blunted. The carotid bodies in the neck may be the site of this effect because they display significant structural enlargement and biochemical changes.
Increased red blood cell production begins on the first day of altitude exposure, due to the production of the hormone erythropoietin by the kidneys. However, this enhanced red blood cell production is accompanied by a decline in plasma volume, as shown in tablepageThe net result is that total blood volume does not increase during the first two months at altitude. After this, red cell volume continues to increase for at least one year, and probably longer. It is possible that this natural polycythemia which is primarily stimulated by trauma, parasites, or malnutrition may be an inappropriate response at altitude, because it may reduce exercise and work performance. Long-term acclimatization, however, increases plasma volume and increases red blood cell mass, thereby enlarging total blood volume.
Bone marrow increases its iron uptake to form additional hemoglobin, beginning after exposure.
The myoglobin muscle's counterpart to hemoglobin; an storage site in skeletal muscle increases.
Muscle fiber cross- sectional area decreases with chronic hypoxic exposure; capillary density remains unchanged or decreases; and mitochondrial density is unaltered. This means that a constant capillary network supplies a smaller muscle mass, resulting in greater delivery.
The ratio of aerobic to anaerobic metabolism increases so that energy production ATP formation is more efficient and the production of lactic acid is smaller. This metabolic adaptation occurs, in part, because the intramuscular content of mitochondrial and respiratory enzymes increases.