What Actually Happens to Your Body Above 8,000 Metres
A t sea level, the air around you contains approximately 21% oxygen. Your lungs breathe it in effortlessly. Your blood captures it. Your brain, your muscles, your organs all function within a narrow physiological range that billions of years of evolution have finely tuned for exactly this atmospheric pressure. At 8,000 metres above sea level the altitude at which Mount Everest's death zone begins the air still contains 21% oxygen. But the atmospheric pressure has dropped to roughly one-third of what it is at sea level. This means your lungs inhale the same proportion of oxygen with every breath, but each breath contains only a third as many molecules. Your body is, in the most literal sense, slowly suffocating in open air. This is not a metaphor. It is physiology. And it explains everything about what happens to human beings at extreme altitude. The First Hour at Altitude: Acute Mountain Sickness Most people ascending to 3,500 metres or above will experience some degree of Acute M...