What is the Death Zone?

In mountaineering, it refers to altitudes beyond 26,000 ft above sea level, where oxygen levels are not sufficient to sustain human life.

The human body functions best at sea level where the atmospheric pressure is 101,325 Pa or 1013.25 millibars (or 1 atm, by definition). The concentration of oxygen (O2) in sea level air is 20.9% so the partial pressure of O2 (PO2) is about 21.2 kPa. In healthy individuals, this saturates hemoglobin, the oxygen-binding red pigment in red blood cells.

In the death zone and higher, no human body can acclimatize. The body uses up its store of oxygen faster than it can be replenished. An extended stay in the zone without supplementary oxygen will result in deterioration of body functions, loss of consciousness and, ultimately, death. Scientists at the High Altitude Pathology Institute in Bolivia dispute the existence of a death zone, based on observation of extreme tolerance to hypoxia in patients with chronic mountain sickness and normal fetuses in-utero, both of which present pO2 levels similar to those at the summit of Mount Everest.

Mountaineers use supplemental oxygen in the death zone to reduce deleterious effects. An open-circuit oxygen apparatus was first tested on the 1922 and 1924 British Mount Everest expeditions; the bottled oxygen taken in 1921 was not used (see George Finch and Noel Odell). In 1953 the first assault party of Tom Bourdillon and Charles Evans used closed-circuit oxygen apparatus. The second (successful) party of Ed Hillary and Tenzing Norgay used open-circuit oxygen apparatus; after ten minutes taking photographs on the summit without his oxygen set on, Hillary said he “was becoming rather clumsy-fingered and slow-moving”.

 

Picture Credit : Google

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