The high elevation is less oxygen and also less pressure, just the opposite. I think the altitude in some locations are just away from pollution and also pollen if above tree line maybe?
I looked at some links on the web page about the treatment in a Hyperbaric Chamber and it was not showing support. This one the Undersea and Hyperbaric Medical Society (UHMS) did have a pdf file link on their finding of other about the use to help with side effects of some specific cancer drugs or combinations. It all was leaving it to more studies.
What I know of is that for nitrogen, as bubbles in the blood, Decompression sickness, that it has been used for quite a while since that it was called caisson disease. See the documentary of a designer of the Brooklyn Bridge where the term caisson disease came from. A father engineer and his son that over saw the construction ended with the bridge being built and his son getting the bends and leaving him disabled as well as many workers.
about the Roeblings'.
No one knew what coming up too quickly after staying down at depth too long was about. They were doing excavation and making the pilings for the bridge. If they could have kept the pressure in the chambers at sea level and somehow they were strong enough not to be crushed, then no one would have been disabled or died from the nitrogen. An alternative is mixing up Oxygen and Helium or another inert gas Argon could have also prevented this. Argon is a heavy gas so it also keeps you warmer and your voice does not get that high pitch. I saw an episode of Sea Hunt and they did not get that part right about voice chaining with breathing helium. I have watched documentaries with the designer of the aqualung and his son, Jacques-Yves Cousteau & Jean-Michel Cousteau, where I found it difficult to comprehend the voices at that high pitch. But the show Sea Hunt with Mike (Lloyd Vernet Bridges, Jr.) is interesting anyway.