Today more than 3,500 people have reached the summit of Everest, but only 5 percent, or 161 people, have done so without oxygen: 35 Sherpas with no deaths, 117 Westies with 10 deaths. The late, great Russian climber Anatoli Boukreev, author of The Climb: Tragic Ambitions on Everest, made three ascents of Everest without Os, and super-Sherpa Ang Rita from Yilajung, Nepal, made ten oxygenless ascents
To Os or Not to Os – National Geographic
Unlimited Potential, Up to 8000m 