Physiological differences of breath holds? What is happening in the body with oxygen and carbon dioxide when we hold our breath and then when we hold a retention? What are the differences?

Hello! My 1st time posting on here as have discovered I need 'likes' to gain access to other Levels of fabulous breathwork practices on this site. So please throw me a few likes :) I have not long completed day 28 of the MB30! Wow! Just love these morning activation practices. I have noticed a greater sense of general calm/steady-ness within myself. However, also some very painful emotions/trauma/reactions have surfaced in a very powerful way. This is good, but intense. I feel like my system is purging, I am grateful for this. C x

Releasing 5 traumas - thankyou! Life's conditioning has been a heavy chain I have been dragging around - it is so liberating to feel some freedom after completing this practice. Loving the intensity Brian!