Depends on the approach you want to take. It's possible but IDK if you'd see any sort of health benefits from simply lowering the CO2, you'd probably also want to increase the O2 content.

This is actually a crazy thing that some of the very wealthy are doing in mountain homes. They have O2 tanks setup with their homes so that when they arrive they don't experience altitude sickness.

https://www.outsideonline.com/outdoor-adventure/snow-sports/...