Suspension trauma, or orthostatic intolerance, is a natural human reaction to being upright and immobile, where blood pools in the legs leading to unconsciousness. It can be caused by suspension in a harness (deliberate or accidental), when trapped in a confined space, when secured to a vertical stretcher or litter - any situation where you are forced to stay upright without standing. If it is allowed to develop unchecked, it will be fatal.
This website provides free, impartial advice on how to deal with the risks of suspension trauma, both at work and at play. It also gives in-depth guidance for medical staff and first responders, as it is not part of the normal first aid, EMT or paramedic training in most countries.