- Death zone
The death zone, in
mountaineering , refers toaltitude s above a certain point where the amount ofoxygen cannot sustainhuman life. The point is generally tagged as between 7000 meters (22,950 feet)cite web |url= http://www.8000metres.com/death-zone |title= The Death Zone|work= Andy|publisher= 8000 metres|date= 2005-06-07] to 8000 meters (26,250 feet).cite web
url= http://www.pbs.org/wgbh/nova/transcripts/2506everest.html
title= Everest:The Death Zone
work= Nova
publisher= PBS
date= 1998-02-24] Many deaths in high-altitude mountaineering have been caused by the effects of the Death zone, either directly (loss of vital functions) or indirectly (wrong decisions made under stress, physical weakening leading to accidents).Physiological background
The
human body functions at its best atsea level , where theatmospheric pressure is measured at 1 atm. Thehemoglobin (the oxygen-binding red pigment inred blood cells ) is saturated withoxygen (nearly 100 %) at that air pressure. [cite web
url=http://www.flightstat.nonin.com/documents/Hypoxia,%20Oxygen%20and%20Pulse%20Oximetry.pdf
title=Hypoxia, Oxygen, and Pulse Oximetry
work=FlightState Pulse Oximeter
accessdate=2006-12-29]At higher altitudes, the air pressure drops and so does the amount of available oxygen. At 5,000 meters (16,400 feet, height of
Mount Everest base camp ), the amount of oxygen is only half that at sea level. At 8,848 meters (29,029 feet, summit of Mount Everest), only one-third as much is available. [cite web|url=http://www.physicalgeography.net/fundamentals/7d.html|title=Introduction to the Atmosphere|work=PhysicalGeography.net|accessdate=2006-12-29] When thepartial pressure of oxygen drops, the human body tries to compensate by a process known asaltitude acclimatization . Additional red blood cells are manufactured, the heart beats faster, non-essential body functions are temporarily shut down, food digestion efficiency declines (as the body shuts thedigestive system down) [ cite journal | last =Westerterp | first =Klaas | authorlink = | coauthors = | year =2001 | month =June | title =Energy and Water Balance at High Altitude | journal =News in Physiological Sciences | volume =16 | issue =3 | pages =134–137 | pmid =11443234 | url =http://physiologyonline.physiology.org/cgi/content/full/16/3/134 | accessdate = | quote = ] and one breathes more deeply and more frequently. However, acclimatization cannot take place immediately – in fact, it takes place over a period of days or even weeks. Failure to acclimatize may result inaltitude sickness , includinghigh altitude pulmonary edema (HAPE ) orcerebral edema (HACE ). [cite web
url=http://www.princeton.edu/~oa/safety/altitude.html
title=Outdoor Action Guide to High Altitude: Acclimatization and Illnesses
work=Outdoor Action First Aid & Safety Training
accessdate=2006-12-29]At extreme altitudes (above 7,500 meters, 24,600 feet), sleeping becomes very difficult, digesting food is near-impossible,Fact|date=February 2007 and the risk of HAPE or HACE increases greatly.Fact|date=February 2007
Finally, in the "death zone" at 7,000 (22,950 feet) - 8,000 meters (26,250 feet) and higher, no human body can acclimatize. An extended stay in the zone without supplementary oxygen will result in deterioration of body functions, loss of consciousness and ultimately, death.
ee also
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August 2008 K2 climbing accident References
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