The death zone in mountaineering, (originally the lethal zone) was first conceived in 1953 by Edouard Wyss-Dunant, a Swiss physician and alpinist. It refers to altitudes above a certain point where the amount of oxygen is insufficient to sustain human life for an extended time span. This point is generally tagged as , less than 356 millibars of atmospheric pressure). All 14 summits in the death zone above 8000 m, called eight-thousanders, are located in the Himalaya and Karakoram mountain ranges.