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Suspension trauma, also known as Harness Hang Syndrome (HHS) is an effect which occurs when the human body is held upright without any movement for a period of time. If the person is strapped into a harness or tied to an upright object they will eventually suffer the Central Ischaemic Response (commonly known as Fainting). If you faint and remain vertical you will die due to your brain not receiving the oxygen it required. People at risk of suspension trauma include people using industrial harnesses (fall arrest systems, abseiling systems, confined space systems), people using harnesses for sporting purposes (caving, climbing, parachuting, etc), stunt performers, circus performers, and so on.

In normal life this problem does not occur because when we walk our veins naturally move blood back out of our legs, but when movement is restricted and we are stuck standing still we naturally faint to recover. Ordinarily, falling to the ground after fainting, would have the effect of raising the legs relative to the heart, and consciousness would soon return.

Averting Suspension Trauma is a major part of Cave rescue, Rope rescue and similar fields. Tests have shown that healthy, rested individuals sitting immobile in standard harnesses will usually lose consciousness around 6 minutes, and no more than 10 minutes, and sometimes even as rapidly as 3.5 minutes. Individuals who are not starting out in such a good situation, due to exhaustion, injury, hypothermia and so on are presumably at even greater risk. Because of this, if a person is found to be stranded in their harness time is of the essence for rescuing them.

Symptoms begin with an overall feeling of illness, similar to influenza, excessive sweating, nausea, dizziness and hot flashes. Observers will notice brain function impairment that deteriorates rapidly. As the situation develops, there will be difficulty in breathing, elevated heart rate, cardiac arrythmias, an abrupt increase in blood pressure followed by unconsciousness, and death shortly thereafter.

Prevention of Suspension Trauma is greatly preferable to trying to deal with the consequences. Specific recommendations are for individuals doing technical ropework to be careful not to exhaust themselves so much that they end up without the energy to keep moving, make sure everybody in a group is trained in single rope rescue techniques, especially they should know how to do a single rope pickoff, a rather difficult technical manoeuver that must be frequently practiced in order to perform it smoothly. If someone is stranded in a harness, but is not unconscious or injured, and has something to kick against or stand on (such as a rock ledge or caving leg-loops) it is helpful for them to use their leg muscles by pushing against it every so often, to keep the blood pumping back to the torso. If the person is stranded in midair or is exhausted, then keeping the legs moving can be both beneficial and rather dangerous. On the one hand, exercising the leg muscles will keep the blood returning to the torso, but on the other hand, as the movements become weaker the leg muscles will continue to demand blood yet they will become much less effective at returning it to the body, and the moment the victim ceases moving their legs, the blood will immediately start to pool. "Pedalling an imaginary bicycle" should only be used as a last-ditch effort to prolong consciousness, because as soon as the "pedalling" stops fainting will shortly follow.

If it is impossible to rescue someone immediately, then it is necessary to raise their legs to a sitting position, which can be done with a loop of rigging tape behind the knees or specialized equipment from a rescue kit. During and after the rescue it is important not to allow the subject to lie on the ground, as this can cause heart attack and multiple organ failure—they must be kept sitting upright for at least 30 minutes after the rescue, and these instructions must be forced upon any ambulance crew attending the scene. It is imperative to get the patient to a hospital as soon as possible, to avoid life-threatening complications due to reflow syndrome, compartment syndrome, reperfusion injury. These complications may not become obvious for hours or even days after the event, by which time irreperable damage may have occurred.

• Orthostatic intolerance

• www.suspensiontrauma.info this is probably the most authoratative source of information. Other publications, even government pamphlets, have been known to give misleading or dangerously out-of-date advice.
• www.texasroperescue.com library

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