Why

CO2 is metabolic. That's why living in the mountains extends lifespan. Go see why folks above >7000ft are the most metabolically healthy people in America.

Thanks

The percentage of CO2 stays the same at altitude. The partial pressure changes and I think that that has more to do with your body not being able to offgass/respirate CO2 as efficiently. I don’t know if high CO2 environments are actually metabolic if they are artificial. I have seen it in plants, not animals. The mental performance hit of high CO2 seems real enough…