• About The Patch Expedition
• Climbing in Aid of Unicef
• Meet The Team
  • The Patch Team
• Corporate Sponsors
  • Become a Corporate Sponsor
• Training for Everest
  • Technical
  • Physical
  • Mental
  • Nutrition
• Climb Your Own Everest
• Climbing Everest
  • Everest Facts
  • The Gear
  • The History of Everest
  • The Route
  • Altitude and Illness
    • Our Bodies and Oxygen
    • Altitude and Oxygen
    • Acclimatisation
    • The Death Zone
    • Supplemental Oxygen
    • Sickness on the Big Hill
• FAQ's

Oxygen at Altitude

The reason climbing, or doing any thing for that matter, at altitude is so difficult is because our bodies get starved of oxygen. Contrary to popular belief, the percentage of oxygen in the air doesn’t change significantly with altitude. In fact the percentage of oxygen at the summit of Everest is still approximately 21%, the same as that at sea level. So why do climbers feel out of breath when they are high up on the mountain and why do most require supplemental oxygen to climb Mount Everest? This is all to do with pressure.

The higher and further away from sea level you are, the lower the atmospheric pressure. The atmospheric pressure determines the density of the air, therefore in effect the higher you go the less air there is to breath. So although the percentage of oxygen doesn’t change, the number of oxygen molecules available to breath reduces the higher you climb. At 18,000 feet the atmospheric pressure is approximately 50% of that at sea level, therefore each breath only brings in about half the number of oxygen molecules. At the summit of Everest the amount of oxygen is less than a third of that available at sea level.

As well as reducing the amount of oxygen available, altitude also effects the transport of oxygen around the body. At sea level the atmospheric pressure helps force oxygen from the lungs into the blood and then the tissues. However, as the pressure drops at higher altitudes, it is much harder for oxygen to get to where it is needed.