How suspension trauma happens

摘要

Our bodies are not ideally designed for being upright. Our hearts are quite high up in the body and can't suck blood up from the legs, so whenever we are upright, gravity is pulling our blood down into our legs. The only thing that stops it staying there is a process of muscular pumping. The major veins in the legs are routed through the muscles, and so when we use those muscles, the blood is squeezed back up. This works well so long as we are using the muscles. Walking about is fine, but if we stand upright and keep still, the blood starts to pool in our legs. The brain is the most demanding organ in terms of blood and oxygen supply. It cannot survive without oxygen, but when we are upright it's in the worst position to get it - right at the top of the body. It does, however, have the ability to control its fuel supply, as pressure sensors (baroreceptors) in the head measure the blood pressure and can then change the heart rate and breathing to compensate. The problem is that the brain can't tell the difference between blood pooling in the legs and blood loss from bleeding. The way it reacts is the same, and this can make things a lot worse for someone in a harness.