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The concentration of oxygen (O 2) in sea-level air is 20.9%, so the partial pressure of O 2 (pO 2) is 21.136 kilopascals (158.53 mmHg). In healthy individuals, this saturates hemoglobin , the oxygen-binding red pigment in red blood cells .
Air contains 20.95% oxygen. At 11,900 m (39,000 ft), breathing pure oxygen through an unsealed face mask, one is breathing the same partial pressure of oxygen as one would experience with regular air at around 3,600 m (11,800 ft) above sea level [citation needed]. At higher altitudes, oxygen must be delivered through a sealed mask with ...
Altitude acclimatization is the process of adjusting to decreasing oxygen levels at higher elevations, in order to avoid altitude sickness. [17] Once above approximately 3,000 metres (10,000 ft) – a pressure of 70 kilopascals (0.69 atm) – most climbers and high-altitude trekkers take the "climb-high, sleep-low" approach.
In the region from sea level to around 3,000 m (10,000 ft), known as the physiological-efficient zone, oxygen levels are usually high enough for humans to function without supplemental oxygen and altitude decompression sickness is rare. The physiological-deficient zone extends from 3,600 m (12,000 ft) to about 15,000 m (50,000 ft).
Smoking drastically reduces oxygen intake efficiency, and can have the effect of reducing tolerance by 1,000–2,000 metres (3,300–6,600 ft). [4] Hypoxia can be produced in a hypobaric chamber. This can be useful for identifying individual symptoms of hypoxia, along with rough estimates of the altitude that causes problems for each person.
By contrast, the women of long-resident, high-altitude populations are known to give birth to heavier-weight infants than women of the lowland. This is particularly true among Tibetan babies, whose average birth weight is 294–650g (~470) g heavier than the surrounding Chinese population, and their blood-oxygen level is considerably higher. [24]
About 1 in 50 climbers who ascended Denali [6,194 metres or 20,322 feet] developed pulmonary edema, and as high as 6% of climbers ascending rapidly in the Alps [4,559 metres or 14,957 feet]. [9] In climbers who had previously developed HAPE, re-attack rate was up to 60% with ascent to 4,559 metres (14,957 ft) in a 36-hour time period, though ...
Atmospheric pressure decreases with altitude while the O 2 fraction remains constant to about 85 km (53 mi), so PO 2 decreases with altitude as well. It is about half of its sea level value at 5,500 m (18,000 ft), the altitude of the Mount Everest base camp, and less than a third at 8,849 m (29,032 ft), the summit of Mount Everest. [8]