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At very high altitude, 3,500 to 5,500 metres (11,500 to 18,000 ft), maximum SaO 2 falls below 90% as the arterial PO 2 falls below 60mmHg. Extreme hypoxemia may occur during exercise, during sleep, and in the presence of high altitude pulmonary edema or other acute lung conditions. Severe altitude illness occurs most commonly in this range.
The medical problems that are direct consequence of high altitude are caused by the low inspired partial pressure of oxygen, which is caused by the reduced atmospheric pressure, and the constant gas fraction of oxygen in atmospheric air over the range in which humans can survive. [1]
Re-entry HAPE is also an entity that has been described in persons who normally live at high altitude but who develop pulmonary edema after returning from a stay at low altitude. [3] If HAPE is not treated, there is a 50% risk of mortality. [4] Symptoms include crackling sounds when breathing, dyspnea (at rest), and cyanosis. [4]
CMS was first described in 1925 by Carlos Monge Medrano, a Peruvian doctor who specialised in diseases of high altitude. [3] While acute mountain sickness is experienced shortly after ascent to high altitude, chronic mountain sickness may develop only after many years of living at high altitude. In medicine, high altitude is defined as over ...
Mild cases of the "bends" and some skin symptoms may disappear during descent from high altitude; however, it is recommended that these cases still be evaluated. Neurological symptoms, pulmonary symptoms, and mottled or marbled skin lesions should be treated with hyperbaric oxygen therapy if seen within 10 to 14 days of development. [102]
Rapid altitude changes with accompanying changes in ambient pressure exposed the aircrews to an increasing number of episodes of sinus barotrauma. Referred pain from barosinusitis to the maxilla consists about one-fifth of in-flight barodontalgia (i.e., pain in the oral cavity caused by barometric pressure change) cases.
High-altitude adaptation in humans is an instance of evolutionary modification in certain human populations, including those of Tibet in Asia, the Andes of the Americas, and Ethiopia in Africa, who have acquired the ability to survive at altitudes above 2,500 meters (8,200 ft). [1]
Altitude sickness. Frostbite or hypothermia from exposure to freezing cold air at high altitude. [14] Physical trauma caused by the violence of explosive decompression, which can turn people and loose objects into projectiles. At least two confirmed cases have been documented of a person being blown through an airplane passenger window.