Understanding & Preventing Altitude Sickness (AMS)

The Physiology of Thin Air

At sea level, the effective oxygen concentration is 21%, with atmospheric pressure pushing that oxygen into your blood easily. At Everest Base Camp (5,364m), the oxygen percentage is still 21%, but atmospheric pressure is reduced by 50%. Each breath delivers only half the oxygen molecules your muscles and brain are accustomed to.

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The Golden Rules of Himalayan Acclimatization

1. Climb High, Sleep Low: During acclimatization rest days (such as Namche Bazaar at 3,440m), hike up 400–600m higher to Everest View Hotel (3,880m), rest for 2 hours, then return down to sleep. 2. Limit Sleeping Elevation Gains: Above 3,000m, never increase your sleeping altitude by more than 400–500 meters per night. 3. Mandatory Rest Days: Take an acclimatization day every 3–4 days or after every 1,000m gained. 4. Hydration Benchmark: Drink 3.5 to 5 liters of fluid daily. Dehydration mimics and accelerates AMS symptoms.

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When to Descend Immediately

If mild headache progresses to vomiting, ataxia (inability to walk heel-to-toe in a straight line), or confusion, these are early signs of HACE (High Altitude Cerebral Edema). Rule #1 of the Mountains: The only cure for severe altitude sickness is downward elevation. Descend at least 500–1,000 meters immediately.