Actually I thought that the intestines didn't absorb gasses otherwise we would have methane in our blood.
The body well regulates carbon dioxide in the blood stream because of it's PH. I can create carbonic acid and your body likes to maintain a certain PH so the rest is pushed out through the lungs.
Hyperventalating can actually lower your PH enough to see a difference on a litmus test.
Read "The Andromeda strain" by Michael Crighton? In it, a virus from outerspace kills off an entire town and the only survivors were a baby and a drunk. The baby survived because it screamed alot and lowered it's PH, and the drunk survived because he got high on sterno which raised his PH and the alien bug could only exist at a narrow PH in the body. Hehehe.