Joseph,
As someone who lives in the high altitude of Colorado, I have never heard of actual restrictions. I believe w/ everything I have learned is that the higher elevations are suppose to be another way to contract PAH. I know that that form of contraction is not formally listed as a cause in medical literature as far as I know. What I also know is that in lower elevations a person can exist a lot longer before becoming O2 dependent. I have read where living in the high elevations can also shorten life expectency. I was also told by my first pulmonologist that if I would relocate to a lower elevation I would not be oxygen dependent so soon & that life expectancy can be longer. So that dr. reiterated everything I had read in numerous sources.
Now unfortunately for me, relocating is not now nor will it ever be a possibility. So just another fact I had to come to terms w/ in living w/ this condition, just in case there weren't enough, that was just 1 more added to the list. I also know if someone travels from a low elevation to the higher elevation depending on the individual & where they are w/ this condition, if they don't need oxygen at home they probably will for their duration in the high elevation, that goes hand in hand w/ a person who goes to higher elevation & is on O2 they need to plan on increasing the LPM.
Hope this helps!!!!!!!!!

I live in Scottsdale where the altitude is a very PH friendly 1000 feet. I have found that I cannot visit any places in my state that have high elevations, like the Grand Canyon with 7000 feet or Sedona with just over 4000 feet. And I have elected to no longer fly rather than have to deal with worrying about traveling with O2 or hassling with the other issues air travel would present.

I don't believe there are restrictions, but you may need/need more oxygen at higher altitudes. I also live in CO. Moving isn't a realistic option. Plus, now I have a grandbaby. I don't know how long I will have with her. I've been here 28 years and get altitudes sickness going to Estes Park. Lol. If you're on O2 already, shouldn't be an issue. Did not know it can shorten lifespan. Oh well.