[N_Lens]

I've read that book and also Patrick McKeown's 'Oxygen Advantage', which also talks about CO2 tolerance and the benefits of Buteyko.

https://www.amazon.com/Oxygen-Advantage-Scientifically-Breat...

https://www.youtube.com/watch?v=-m8jIhQyiDY

Good stuff honestly, helped me a lot