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Oxygen
Whether you're at sea level or high on a mountain, the atmosphere holds the same level of oxygen: 21 per cent. As people climb higher, however, they experience less atmospheric (barometric) pressure, and the oxygen molecules are farther apart, making it harder to breathe. Whether you're at sea level or high on a mountain, the atmosphere holds the same level of oxygen: 21 per cent. As people climb higher, however, they experience less atmospheric (barometric) pressure, and the oxygen molecules are farther apart, making it harder to breathe.
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Acclimatisation
At sea level, atmospheric pressure helps force oxygen from the lungs into the blood and tissues. At higher altitudes, as the pressure decreases, this process slows down. The body responds by increasing the number of red blood cells, which carry oxygen, as well as increasing production of an enzyme that transfers oxygen to the tissues. Mountaineers know it takes time for the body to adjust to the decrease in oxygen at higher altitudes.
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Acute mountain sickness
Commonly known as altitude sickness, AMS affects all climbers to some degree. Among the biggest complaints are headaches, nausea and vomiting, dizziness and insomnia. AMS is usually not serious, but its symptoms may be early indications of pulmonary oedema or cerebral oedema.
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High-altitude pulmonary oedema
If the pressure within a climber's lungs becomes too great, plasma (the liquid part of the blood) may leak into the alveoli of the lungs. As the lungs fill with fluid, the climber may suffer from shortness of breath, chest pain, wheezing and coughing. Most fatal cases occur above 3,600 metres.
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High-altitude cerebral oedema
Increased blood flow to the brain in response to its call for oxygen produces swelling which may initiate confusion, drowsiness, hallucinations and coma in the climber. This is potentially fatal, but patients can recover completely if treated immediately at a lower altitude.
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Lack of judgement
Decreased oxygen to the brain can cause climbers to experience a lack of mental clarity. Climbers may forget to eat, or even lose their sense of direction. Their memory may fail them and some might be unable to speak normally.
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Ataxia
Climbers need good balance, coordination and manual dexterity, but the part of the brain that controls these abilities requires a lot of oxygen to function correctly and as the air thins at altitude, the supply of oxygen also thins, resulting in a potential loss of coordination and balance.
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Sleep disturbance
During sleep, decreased oxygen levels may trigger the climber's breathing to become sporadic, with several deep breaths followed by several seconds of no breaths at all.
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Dehydration
The effects of deeper, harder breathing at altitude mean even more water than normal is being lost from a climber's body, via his or her lungs.
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Weight loss
Many climbers lose their appetite at high elevations. The intestines may play a role in weight loss too, by failing to absorb some foods (particularly fats) as efficiently as they normally would.
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Blood clotting
Red blood cell production increases at altitude over one to two months, causing blood to thicken, which may cause clotting in some chambers. Another likely source of clotting is dehydration at high altitudes.
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High altitude toothache
This painful condition occurs when a pocket of air gets trapped in fillings. It can irritate a nerve, loosen the filling or even pop the filling out from the pressure of high altitude.
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High altitude flatus expulsion
This condition arises at altitude when climbers may detect an increase in the normal amount of gas in their intestines due to changes in the atmospheric pressure.
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Snow blindness
The higher someone climbs, the greater his or her exposure to dangerous ultraviolet radiation. In fact, for every 300 metres of elevation, ultraviolet light exposure increases by about four per cent. So climbers at the top of Everest are exposed to nearly 30 times the UV light they would face at sea level. Snow on the ground only makes matters worse, as it can reflect 80 per cent of the ultraviolet light.
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Sunburn
Sunburn poses a real danger. Climbers need to wear sunscreen with an SPF of at least 30, and reapply it at least every two hours during the day.
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Frostbite
A climber who starts to lose feeling in any extremity needs to warm up immediately, as severe frostbite can damage fingers, toes, feet and other body parts so badly that they may ultimately need to be amputated.
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Pneumonia
At altitude, dust, dry air, the climber's increased respiratory rate and relative dehydration can sometimes lead to pneumonia. The resultant severe coughing - on Everest this is called the "Khumbu cough" after the glacier - is often enough to break a rib. Pneumonia must be treated with antibiotics.
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Hypothermia
A pathologic reaction of body temperature leading to impaired judgment, clumsiness, slurred speech, weakness and progressive mental impairment and ultimately, loss of consciousness and heart dysfunction.
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