We often hear the term “Suspension Trauma” used to describe a person becoming unconscious after being suspended in a harness, this is outdated and most importantly; used incorrectly.
The word “Trauma” is used to describe a physical injury like a bleed, organ damage or a broken bone which is not the reason for the loss of consciousness here. It is actually “Orthostasis”, being held motionless in vertical suspension which causes unconsciousness. Some form of trauma is likely during any significant fall and this could cause or speed up the loss of consciousness such as severe blood loss, (you could refer to this as “suspension trauma”, trauma relating to/caused by a fall, but it adds unnecessary confusion).
In this specific scenario the loss of consciousness is not due to any physical injury but vertical, motionless suspension. So “Trauma” isn’t technically correct, it is far better to use the word “Syndrome” to define the collection of signs and symptoms we refer to as “Pre-syncope” and “Syncope”.
“Pre-syncope” refers to how the casualty feels before losing consciousness, such as: light-headedness, nausea, tingling or numbness of the arms or legs. “Syncope” is when the casualty losses consciousness.
Suspension Syndrome is caused when harness leg straps cause pressure up into the groin when left suspended. This causes blood to start pooling in the legs. Being motionless aggravates the situation further as our muscles usually aid in return blood flow when we move around, we call this the Muscle Pump. The harness straps will squash the veins a bit but not the muscular arteries, this means blood can flow into the legs but struggles to get back out and to the heart, (it does not entirely occlude or close the vein). When less blood gets back to the heart less blood is pumped to the lungs and on to the brain; we call this “reduced cardiac output”. This lack of oxygen getting to the brain will eventually cause unconsciousness or Syncope.
The effects are far greater in un-padded fall arrest harnesses.
Being suspended against your chest such as when we attach fall arrest lanyards to the rear of your harness can increase pressure in the chest which can further reduce blood return.
Some people are a lot more likely to suffer Suspension Syndrome due to things like, fitness, dehydration, alcohol and prescribed medication.
Suspension Syndrome is not a crush injury, although in theory it is possible for a build-up of by products such as Potassium along with blood with little oxygen to return to the heart; this is sometimes referred to as “Reflow Syndrome”.
You must have a rescue plan.
A casualty who is experiencing pre-syncopal symptoms or who is unconscious whilst suspended in a harness, should be rescued as soon as it is safely possible.
If the rescuer is unable to immediately release a conscious casualty from a suspended position, elevation of the legs by the casualty or rescuers where safely possible as well as leg movement may prolong tolerance of suspension.
Once on the ground you should follow basic first aid procedures.
Evidence-based review of the current guidance on first aid measures for suspension trauma http://www.hse.gov.uk/research/rrpdf/rr708.pdf
Advice for first-aiders responding to harness suspension incidents http://www.hse.gov.uk/firstaid/whats-new/harness.htm
CAMP Suspension Trauma: The “SOSPESI” Project https://www.camp-usa.com/safety/technical-info/suspension-trauma-research/