Seems like this is a type of freeze, as in fight, flight, or freeze. Rory Miller says that when a violent event happens the first thing to do is break the freeze that normally consumes us. That is done by taking two actions, preferably actions with movement you can see. Shouting is good too. When people freeze, sometimes they imagine themselves acting instead of actually acting which just continues the freeze. One action isn't enough because one could just refreeze, which might happen anyway which would mean it's time for another two actions.
Alan suggests that an increase in "Body Sense" will improve breathing. This is partly a vocabulary problem but he is also partly wrong. What causes a freeze, or shallow breathing, or constricted breathing is the retreat of a persons spacial mind to their own body. In normal social interactions the spacial mind is a bubble around the body. The bubble is always changing, sometimes it is big, imagine a couple of cowboys smoking rollies on the front porch; and sometimes it is small, imagine polite people on a crowded subway. Stand on a stage confidently and joyously singing the national anthem and the spacial body will get big. On the other hand, with stage fright the bubble becomes like plastic wrap on the body. In a challenge confrontation between two males of the same tribe, these spacial body bubbles stay close to the body in order to de-power the confrontation--because the goal is for one guy to submit to the others dominance, not to do life threatening damage.
Allow me to go a little deeper. There are two bodies. An inner body which is primitive, clumsy, very powerful, without memory, it has simple desires and doesn't carry around preferences. Then there is an outer body, this is the body with muscles, and shapes and pain that most people think of and feel as a body. When the mind sets these two bodies against each other we get all the things that only people can do, like playing baseball and writing letters. There are tons of variations in how these two bodies can mix, but they all include some sort of retreat of the spacial mind into the physical mass of the bodies. The mind is amazing, it can be active both inside and outside the bodies.
There is a simple difference between a male asserting a dominance challenge and a woman experiencing constricted breathing while listening to idiots rant. They both have a shrunken spacial mind with an outer body that is constricting their movements. In the case of the male asserting dominance the spacial mind will suddenly grow then suddenly shrink in a tit for tat dance with the other male. His inner body will be very active, the slang for it is "chomping at the bit," the more he "cuts loose" the more his outer body lets the inner body act--'though he will still be self restricting. The woman with constricted breathing is trying to force the inner body to stay still by constricting it with the outer body. The inner body wants to go bananas but this is socially unacceptable so the mind uses the outer body to contain it by shrinking the spacial mind tight to the surface of the body. It can be quite painful, especially in the abdominal region and around the neck and shoulders.
So to answer Loretta's question, basically you want something that will literally lift your spirits--making your spacial body big. An action that will get your spacial mind outside your body. A big loud socially rude sign could work. Aaaaggghhh! Bleachhhhh! Going to a window sticking your head out and shouting something silly at the birds. Running for the door? Basically action trumps inaction. Throw your arms to the sky and say in your deepest rumbling atheist voice, "Oh God Almighty!" Whatever it is you do, it has to be inappropriate. It has to be rude. Maybe get right in between the ranters, grab them around the waist or the shoulders and say in the most May West voice you can muster, "Heeeeyah, can we talk about SEX NOW?"