• 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

Acclimatisation

In order to climb at altitude all climbers must first allow their bodies to acclimatise. Acclimatisation is the process by which our bodies adjust to a change in the environment. On Everest this means adjusting to lower levels of oxygen.

When on an Everest expedition, a climber spends a lot of time and effort getting their bodies to adjust to the altitude. Although not an exact science, the common method for acclimatisation is to expose the body to incrementally higher altitudes and then either rest at that level or return to a lower altitude to allow the body to recover and produce more red blood cells.

In practise, as the levels of oxygen at Base Camp are only half that at sea level, even the trek up to the mountain forms part of the acclimatisation. This means taking regular rest days during the trek in, especially after days of significant increases in altitude. Once at Base Camp the climbers will rest again to allow their bodies to recover before beginning the 'acclimatisation rounds' up the mountain. For most climbers their acclimatisation schedule will look something like this:

• Climb from Base Camp up to Camp 1 and spend the night before returning to Base Camp
• Rest at Base Camp
• Climb from Base Camp to Camp 1 and from Camp 1 to Camp 2. Stay a night at Camp 2 before returning to Base Camp
• Rest at Base Camp
• Climb from Base Camp to Camp 1 and from Camp 1 to Camp 2. Stay a night at Camp 2 before climbing up to Camp 3. Stay a night at Camp 3 and return to Camp 2. Stay the night at Camp 2 before returning to Base Camp.
• Trek down to Dingboche, a lower altitude to help the body recover and produce red blood cells faster
• Return to Base Camp

Once the acclimatisation rounds are complete the climbers are considered ready and wait at Base Camp for a window of good weather to permit a summit attempt.

In most adults complete acclimatisation is possible up to altitudes of approximately 5,000 to 5,500 metres. Above this elevation however there is a fine balance between acclimatising to altitude and deterioration. Above 8,000 metres the levels of oxygen are so low that climbers are unable to acclimatise as the body uses up its stores of oxygen quicker than it can replenish them. Prolonged exposure at this altitude results in the deterioration of the climber's condition and eventually death, this is why it is referred to as the 'Death Zone'. The only course of action for spending long periods in the Death Zone is to use supplemental oxygen, also known as the 'O's'.