It’s possible for climbers (though a climber doesn’t experience the rapid decompression that a jumper would).
Mount Everest at 29,028 feet is significantly higher than the 23,000 foot fall that Ivan Chisov survived, yet a few rare people have climbed Everest without oxygen:
“Reinhold Messner championed the cause for ascending Mount Everest without supplementary oxygen. In 1978, he reached the summit of Everest with Habeler. This was the first time anyone had been that high without supplemental oxygen and Messner and Habeler achieved what certain doctors, specialists, and mountaineers thought impossible.”[1]
Messner went on to climb all fourteen eight-thousanders (the 14 mountains that are more than 8,000 metres or 26,247 feet) without supplemental oxygen.
They acclimate for a fairly long period of time and still most people who try fail.
It’s quite likely that those who succeed were genetically predisposed to do so rather than just making it on sheer will.
There is a good reason why athletes do high altitude training camps it can boost your oxygen carrying capacity, improve fat oxidation and improve your anaerobic capability.
They were miserable, mountaineers however are used to misery and suffering it is part of the activity.
The hard part is that you become much slower, weaker and you judgement is impaired. Also different people have different ability to adopt. Except for Sherpa who have evolutionary adaptation, in normal population there are not that many people who can do it even if they trained their whole life.
No oxygen climbing if you can do it is in some way safer. You go faster, you do not depend on heavy canisters. You do not need to stock upper camps with oxygen. All of this minimizes objective danger(avalanche, serac falls etc) the shorter you are up the safer you are.
I read that Everest climbers start with as many as 70 tents. Most are to hold supplies (and other tents) at progressively higher/smaller camps, eventually resulting in the last tent at the highest camp before the attempt on the peak.
So dozens of trips are taken to ferry tents/supplies up to the next camp. Which add risk for every hour on the mountain.
Ah, my bad. Likely dependent on the individual. Found this [0] interesting as it’s focused on aviation rather than climbing:
> 10,000 feet. Night vision is now degraded by 15-25 percent. The blood saturation has dropped to 90 percent and your brain is receiving the absolute minimum supply of oxygen. This is the absolute highest altitude at which you should haveany trust at all in your own performance although your judgment is already severely compromised. Euphoria will prevent true self-assessment of your abilities. Physical hypoxic symptoms such as tingling and headache may not become apparent for four hours ormore at this altitude, although judgment has long gone by the wayside. Above 10,000 feetblood oxygen saturation and performance degrade steeply.
> 14,000 feet. Blood oxygen saturation is down to a dangerous85%. You will be increasingly disabled at this altitude. Vision will dim. You willexperience serious degradation of judgment, memory and thought. The impairment of judgmentwill leave you feeling just fine and confident in your performance, however. If hypoxia isnot recognized and corrected at this stage of impairment, it is unlikely that it will berecognized. You are in serious danger.
16,000 feet. Only 2,000 feet higher than the last assessment, but you will behave as though you had ingested a full load of gin and tonics. Your blood oxygen saturation will have dropped to 79 percent and you will be seriously disabled. Youwill be euphoric, belligerent, disoriented or perhaps all three. You will be irrational,unreliable and dangerous. If you are alone, your chances of survival are decreasingrapidly.
> 18,000 feet. At this altitude you are incapable of any usefulfunction although you may still feel great! Blood saturation has fallen to 71 percent andyour brain is suffering. You will pass out in about 30 minutes.
> 20,000 feet. If you have not already collapsed, it will not belong now. Five to 15 minutes is about the time of useful consciousness at this altitude and prolonged exposure can result in death. Blood saturation has dropped to 71%.
> 25,000 feet. Forget it! Blood saturation has now dropped to lethal levels. Time of useful consciousness is three to six minutes with death followingnot long after that. Above this altitude, suffering a rapid decompression may also result in a condition divers know as the bends and various other pressure related maladies. Remember, this is only HALF as high as some modern civilian aircraft are certified to fly!
Altitude sickness is a thing, so it's not quite that black and white.
People who live at altitude go through physiological changes. My ribcage permanently increased in circumference after living 3000 feet above sea level for over 2.5 years.
I think it is possible to get the bends jumping from really high, so you probably don't want to even be breathing air with nitrogen in it for a while before you even jump!
