My man Steve, a Brazilian Jiu Jitsu practitioner, has a post about breathing while sparring, and how important it is to make yourself breathe.
I recently had a couple of interesting experiences with breathing while sparring.
1. Gumba Frank, a fellow black belt and classmate, is always a challenge in standup sparring. Frank is not only tremendously strong, he also has amazing hand speed (even more amazing that he's around 52 years old) and he is a very skilled counterpuncher. He also, surprisingly for someone in an orthodox stance, relies almost exclusively on his left, front, hand. My best strategy against him is to use my reach and to circle to my left, his right--the opposite of what I would normally do against a right hander. I want to steer clear of his left hook.
I realized a few weeks ago while sparring with him that I felt so anxious (when he hits, it hurts) that my breathing was speeding up and becoming shallow, which was tiring me out. And getting tired is a problem because I do best with him when I constantly move. I had to consciously slow down my rate of breathing and deepen the individual breaths. It helped. I was surprised that I hadn't been aware of that pattern before.
2. Last Saturday, I was grappling and got another 50-something black belt, Warren, in an arm triangle. That's a type of choke where I'm using one of his arms against his neck to help finish him off. Warren is a bit of a street fighter, and he came up with a creative solution: He took his free hand, pinched my nose shut, and covered my mouth with his hand, cutting off MY breath. Nobody had ever done this to me before. Eventually, I had to loosen my grip on him to pry his hand from my mouth, but that allowed him to get free from the arm triangle. People did point out to him later that it was an illegal move, but I was laughing about it, I certainly didn't expect it!