A full-body harness is an indispensable component of any personal fall arrest system, designed to stop a fall and save a worker’s life. While the harness arrests the fall, the resulting motionless vertical suspension introduces a secondary, potentially fatal risk. This danger is the consequence of remaining suspended while awaiting rescue, a condition known as suspension trauma or orthostatic intolerance. Trauma suspension straps provide a simple, highly effective measure to mitigate this danger and buy precious time for rescue.
Physiological Effects of Prolonged Vertical Suspension
Motionless vertical suspension in a harness can trigger a life-threatening medical condition known as orthostatic intolerance, or suspension trauma. The primary danger is the pooling of blood in the lower extremities due to gravity and a lack of muscular movement. When a worker hangs still, the leg muscles are relaxed, preventing them from helping to pump blood back toward the heart via the muscular venous pump.
The harness leg straps, which are designed to distribute the impact force of the fall, can inadvertently act as tourniquets, constricting the major veins in the groin and the backs of the legs. This constriction, combined with gravity, significantly restricts the return of deoxygenated blood to the heart and lungs, causing blood to pool in the legs. With less blood circulating back to the torso, the heart’s output decreases, leading to a rapid drop in blood pressure and a lack of oxygen reaching the brain, which is termed cerebral hypoxia.
Symptoms such as light-headedness, dizziness, nausea, and visual disturbances can begin in as little as five to ten minutes, rapidly progressing to syncope, or fainting. Since the harness prevents the worker from collapsing into a horizontal position, the necessary restoration of blood flow to the brain does not occur. This continued lack of oxygen can lead to unconsciousness and death, sometimes within 15 to 40 minutes, underscoring why prompt rescue is mandated.
How the Straps Relieve Pressure
Trauma suspension straps are small, packaged webbing devices attached to the harness, usually near the hips, and deployed by the suspended worker. The fundamental purpose of these straps is to create a temporary foothold, or stirrup, allowing the worker to change their body position. By deploying and standing in the loops, the worker transfers their weight from the constricting leg straps to their feet.
This action immediately relieves the pressure exerted by the harness webbing on the femoral veins in the upper thighs. When the worker pushes down against the strap, the leg muscles contract, activating the muscular venous pump. This muscle contraction helps push the pooled blood out of the lower extremities and back into the central circulation, interrupting the cycle of orthostatic intolerance.
The straps are not a rescue device but a temporary self-aid measure that extends the time a worker can safely remain suspended while waiting for rescue. They are designed as a continuous loop, allowing the worker to step into the stirrup with one or both feet for adjustable support and better balance. By restoring blood flow, the worker remains conscious, can communicate with rescuers, and maintains a stable physical state for a longer period.
Post-Fall Deployment Procedure
Immediately following a fall arrest, the worker must prioritize deploying the trauma suspension straps to prevent suspension trauma. The worker should first locate the small pouches containing the straps, usually secured to the harness webbing on either side of the waist. After locating the pouches, the worker must quickly release the closure mechanism, often a zipper or hook-and-loop fastener, to deploy the full length of the webbing.
Once the strap is released, the worker connects the two ends of the webbing to form a continuous loop or stirrup, often using a clipping or hook-and-loop system. The worker then places one or both feet into the loop and uses the foothold to push down and stand up, shifting body weight off the harness leg straps. The strap length is often adjustable to ensure the worker can stand comfortably and relieve the sub-pelvic pressure.
Even while standing in the deployed stirrups, the worker should actively flex and “pump” their leg muscles by moving their feet up and down. This rhythmic movement is crucial for maintaining the muscular venous pump and encouraging blood return to the heart. This self-rescue step is an interim measure, and the worker must maintain movement and communication until rescue is completed.
Upon rescue, the worker should not be immediately laid flat, as a sudden influx of pooled blood to the heart can cause a severe condition known as reperfusion injury or “rescue death.” Instead, the worker should be placed in a semi-reclined or sitting position, often called the “W” position, with the knees bent and close to the chest, for at least 30 minutes. This position allows for a gradual and safer return of circulation while medical services are accessed.