Suspension Trauma

Suspension trauma, also known as orthostatic intolerance or harness hang syndrome, is one of the hottest topics to hit work and rescue at height in rencent years. Although the effects have been known about for a while, it is only since the turn of the millenium that industry regulators, rescue teams and those who wear a fall protection harness as part of their work have started to sit up and take notice.

The Work at Height Regulations require all users of personal fall protection systems (used for fall arrest and work positioning) to be trained in rescue and for work to be planned with the consequences of a fall in mind - so workers should know how and when suspension trauma can arise, and how it may affect their rescue techiques.

What is it?

Suspension trauma is fainting in a harness. It can happen to anyone who is held in an upright position and with their legs immobile. You don't need to be ill, injured or even in a harness to suffer the condition and it can start to effect you within a matter of minutes. If you don't stop the progress of the condition then you will lose consciousness and in some cases eventually die.

Our bodies are not really 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're upright gravity is trying to pull all our blood down into our legs - the only thing that stops this happening is a process of muscular pumping. The major blood vessels of the legs are routed through the muscles, and so when we walk or climb the blood is squeezed back up, like toothpaste. This works fine so long as we're using the leg muscles with some effort. Walking about is adequate, but if we stand upright and keep our legs still, then the blood slowly starts to pool in our legs. This is the start of problems.

The brain is the most demanding organ in terms of blood and oxygen supply. It can't survive without oxygen and when we're 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 in the neck measure the blood pressure and can then change heartrate and breathing to compensate. The problem is that the brain is a little stupid when it comes to standing upright, and can't tell the difference between blood pooling in the legs and blood loss from bleeding. The way it reacts is the same, and can make things a lot worse for someone in a harness.

The first thing that happens when blood starts to pool in the legs is that the brain increases pulse and breathing rates, thinking you're bleeding. You feel hot, sweaty, dizzy, breathless and anxious as oxygen and carbon dioxide levels change, but as well as pushing more blood to the brain you're also pushing more blood into the legs. Your brain doesn't know this, so doesn't give you some massive desire to raise your knees or ride an imaginary unicycle - both of which would be a much better response! With blood continuing to collect in your legs, eventually the brain realises that it's supply is still dropping. It kicks in the emergency last-resort plan, where you conserve your remaining energy by fainting and lying down. When you fall over, the blood can return to your brain and you wake up within a minute or two, feeling fine. The problem is of course that you can't fall over in a harness.

So, you're unconscious, and still upright. You're now at imminent risk of death, for two reasons. First your airway isn't safe in this position, so you can suffocate. Second, your poor brain now has next to no oxygen and no way to get any more. Just because you haven't fallen over, your brain cannot wake you up again. There is no Plan B.

The initial symptoms (change in pulse, anxiety, etc) occurs in as little as 5 minutes. Most people will feel unwell within 15 minutes. An otherwise-healthy person can lose consciousness in as little as 10 minutes and at that point will be imminently at risk of death. Age, sex, weight and fitness do not influence these results, and the onsets are very varied - some people can tolerate suspension for up to an hour on one day, then only a few minutes on the next. Discomfort from a harness is not an accurate indicator of risk.

The critical factor is not using the leg muscles and being upright. If you're not upright or still actively using your legs, suspension trauma is not going to occur

Harness design

You can see that harness design has little bearing on suspension trauma itself. You don't need constrictive leg loops, and ALL fall arrest harnesses are designed to hold the body upright. A padded high-price harness doesn't prevent suspension trauma, though it does make the first few minutes a little more comfortable. What matters though is how you can get yourself out of this life-threatening situation. Depending on the design of your harness you may find escape easy, or impossible. Read on to see why!

Utimately anyone working in a harness can prevent suspension trauma by using their leg muscles enough to keep the blood pumping back into the torso. This is what happens when people work in a harness but are kicking and climbing against structures. The problem is that keeping your leg muscles moving enough is quite hard work, and if you're unconscious or injured then you may not be able to move them at all.

With your thighs horizontal, the height difference between your heart and legs is smaller and the pooling effect is reduced to a safe level. In other words:

If you're in a sitting position you are at a much reduced risk from suspension trauma

Hanging in a harness isn't a sitting position, but you can get into one if you can raise your knees far enough. If you're in mid-air then you need to make yourself a knee-loop to lift your legs, either from spare rope, hose, tape, clothing or by carrying a dedicated emergency knee-sling device. Your priority as the person who's fallen, or the person helping, is to raise the knees as soon as possible. If you wait 30 minutes it won't help.

Harness attachment points

In fall arrest you have two places to clip yourself on - an upper front point and an upper back point. These are both designed to hold the body upright after a fall and avoid spinal injury from the deceleration forces. Rear attachment points are often preferred as they keep lanyards out of the way when working, but when you take into account suspension trauma, they are potentially lethal. Front points add clutter, but are massively safer.

Rear Attachment Uncluttered Cannot reach own lanyard Knee-raising very difficult Impossible to protect airway Cannot self-inspect attachment point

Front Attachment Lanyard in easy reach Knee-raising very easy Airway protectable by tilting horizontal Attachment point visible for inspection

An A4 information card is available by clicking here.

All the information presented here is sourced with permission from the international guidelines issued by STIS.

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