About breathing..........

I don't know about others, but I know that I unknowingly seem to hold my breath when going through a temporary excruciating pain. It is not something I do on purpose, it just happens at the onset of a painful medical procedure. Then I realize I am holding my breath and have tensed up. I know that holding my breath does not eradicate the pain but it is an automatic reaction. When I realize I am doing it, I try to breath normally.

I am just wondering if others have this "automatic" response when undergoing a painful medical procedure.

Do others breath abnormally when going through elevated pain levels?