|West, J.B. Respiratory Physiology; The Essentials 6th ed. Baltimore: Williams & Williams, 1999: 119-120.||"Highest human habitation at is at 6000 m and 380 mm Hg (barometric pressure)."||6000 m|
|Climbing at Extreme Altitudes above 7000 meters. UIAA Mountain Medicine Center, October 2002.||"Permanent human habitation ceases - due to lack of oxygen, not terrain - above 5400m …. Around 6000m acclimatised climbers may expect to feel well, have reasonable appetites, sleep normally and be capable of carrying loads of 20-25 kilos on easy ground. Ascent rates comparable to those on Alpine routes have been well documented over many years. Above 7000m, the situation changes: the feeling of tiredness and lethargy increases, continuous exercise becomes impossible and climbing even easy slopes becomes a painstaking, breathless achievement"||6000 m|
|Huey, Raymond B. and Xavier Eguskitza. Limits to human performance: elevated risks on high mountains. The Journal of Experimental Biology. Vol. 204 (2001): 3115–3119.||"Heights greater than 8000m are well above the highest human habitation (5950m; West, 1986a) and are inhospitable for sustained human life. Accordingly, such extreme heights are sometimes referred to as the 'Death Zone' (Krakauer, 1997)."||8000 m|
|West, John B. High Altitude Medicine & Biology, Highest Permanent Human Habitation. University of California San Diego, Dec 2002, Vol. 3, No. 4: 400–407.||"Individuals have lived for as long as 2 yrs at an altitude of 5950 m, and there was a miner's camp at 5300 m for several years."||5950 m|
|Jensen, Niels F. Clinical Arterial Blood Gas Analysis [pdf]. Written Board P.R.E.P., 2001.||"The highest human habitation occurs at about 20,000 feet where the PAO2 is in the low 50s."||6100 m|
The maximum or "vertical limit" of human survivability is around 6000 meters. Extreme heights are called "death zones" and are usually above 8000 meters. Heights higher than 8000 meters are inhospitable for sustained human life. Research indicates that humans cannot live permanently above an elevation of 5500 meters (18,000 feet) without suffering a gradual physiological deterioration that eventually leads to death. Mountaineers who anticipate spending time above this altitude have to fatten themselves before the climb to offset their inevitable weight loss.
As the altitude increases, the barometric pressure decreases. The availability of oxygen decreases as the altitude increases. The increase in oxygen content through the increase in the number of red blood cells is one of the most important mechanisms of adaptation to high altitude. As of May 2003, National Geographic Magazine reports that La Rinconada, Peru, is currently the highest permanent human habitation. La Rinconada, a mining village of over 7,000 people in Southern Peru at an altitude of up to 5100 meters, has been in existence for over 40 years.
Monique Anthony -- 2005