Air you breathe out is around 40 thousand ppm (and higher during exertion), and the air in the lungs isn't completely replaced every breath - I doubt there's much measurable difference at the actual alveoli at the levels we're talking about. You'll probably get more of a difference if you're breathing deeper and faster, or just got up to get a coffee or similar.

And interestingly there are studies that show that breathing in air up to 3% co2 (30k ppm) "did not substantially impair either cognitive and motor performance" [0]

[0] https://www.tandfonline.com/doi/epdf/10.1080/10803548.2007.1...

I've found the same. And thinking it through, I can't come up with a mechanism for how a few more CO2 molecules bopping around in a sea of nitrogen and oxygen changes anything about how my lungs exchange the CO2 in my body with air around me. These counts are ppm, nothing!