Jean-Marc Boivin (the Frenchman Ken001 referred to above) paraglided off the summit and landed down on camp 2 on 26 September 1988.
Partial pressure of O2 at sea level is 3 psi; you have to get PPO2 down to about 1.5 psi before blood oxygen saturation dips significantly below 100%.
Ambient pressure at 29,000 feet altitude is 4.6 psi. a mix of 30% O2 should be enough to provide good blood oxygen saturation; breathing pure oxygen at this pressure (or providing pure O2 in a pressurized suit) would be a waste.
It’s worth noting that after all these years, no one has bothered to ascend Everest with a pressure suit.
Even breathing pure oxygen, survival is not possible at those altitudes without using a pressure suit like the one Kittinger wore for those jumps.
Even supposing he had no pressure suit, he would not have developed decompression sickness. The pressure drop from ground to 100,000 feet was rather small (about 14 psi) compared to the kind of pressure drop that a SCUBA diver experiences (up to 50 psi), so he didn’t have much dissolved nitrogen in his blood, and there would have been plenty of time for it to be removed via his lungs during the hours-long ascent. And again, that was all a non-issue anyway because he did use a pressure suit.
Kittenger was pre-breathing pure oxygen for some period of time to flush out N2; the same goes for U2 and SR-71 pilots. Even HALO jumpers will do a flush.
Everest has about 1/3 the atmospheric pressure as at sea level.
To put this in perspective, the pressure difference of jumping from the top of Everest to sea level would be equivalent to jumping into water and swimming to a depth of 22 feet.
That jump would cover a substantial horizontal distance.
If you’re potentially going to be exposed to a rapid decompression event that does not include timely recompression, then reducing your N2 levels beforehand makes sense. A U2 or SR-71 that experiences loss of cabin pressure at cruise altitude (>70K feet) is going to take a while to descend to an altitude where nitrogen dissolution isn’t a serious risk.
OTOH, Kittinger’s ascents took something like 90 minutes to reach peak altitude, and he would have been breathing pure O2 (and dumping N2 from his body) the entire way up. I’m a little puzzled as to why he would need to pre-breathe O2 before even beginning the ascents.
As for climbing Everest…that takes days, during which time there’s plenty of opportunity for a climber’s body to dump N2 on the way up.
Kittinger and the SR71/U-2 pilots were/are wearing full pressure suits. My understanding is that before they close their visors, the suits are flushed with 100% O2 to ensure that there is no residual N2 that could be reincorporated into the body.
As for Mt. Everest: the main reason you carry oxygen is to stay warm. As you go higher, the cells become increasingly inefficient. This, in turn, decreases the amount of energy generated for basil metabolism. The body, then, has to expend more effort to maintain this level. The cost is less heat is generated, which in turn means other processes become more inefficient; such as breathing, climbing, digestion, thinking, etc. Compounding this problem is the energy expended for breathing as you go higher. Read about the 1st accent of Everest without oxygen..
The upshot is you’re going to be colder climbing Everest without supplemental oxygen. The lack of oxygen also increases High Altitude Pulmonary Edema, hypothermia, frostbite, etc. And most crucially, the ability to make critical judgements when things go wrong.
It’s also fortunate that Everest is located as far south at it is; thanks to the earth’s rotation, the air is just a thick enough to support a summit attempt on calm days. If Everest were in Alaska, or Antarctica, the air would be too thin for an O2-free accent. Even so, the summit of Everest is on the absolute hairy edge of survival; if a storm comes through (let’s forget about the cold, blizzard conditions for a moment) and the barometric pressure drops enough, your cognitive abilities could be disabled to the point you would be essentially a zombie unable to move…
Didn’t Bear Grylls try this? I’m sure I saw a program about it on Discovery Channel.
Naw, you’re thinking about the episode where he lava surfs.
Russian climber, Valery Rozov, did a wing jump from Shivling at 6543 meters (21466ft) today. He jumped 2200 meters onto the glacier below, basically back to base camp.
He did it with a powered paraglider