If you mean suits worn with the purpose of regulating blood flow during high-G aircraft maneuvers, here you go.
The problem during high-G maneuvers is that blood can flow in irregular ways, being pushed towards the outside of the turn like a centrifuge.
In order to counteract this, a G-suit squeezes selectively to create pressure that prevents excess blood from flowing into that part of the body. Most commonly this is the legs to prevent a lack of blood to the brain.
The mechanism for this, at least the known ones, is liquid flowing into bladders to apply pressure.