Fun fact: your intestines are also lungs. Or maybe more accurately, lungs evolved from intestines. It turns out, you can oxygenate people by sticking an oxygen supply up their ass. Which is a possible treatment for people who have suffered respiratory failure.

Proof that I'm not just blowing hot air up your butt, except maybe I am: https://www.science.org/content/article/mammals-can-breathe-through-their-intestines

He was out of breath.