Harness-Induced Pathology - The Dangers of Suspension Trauma

Working in vertical rescue environments presents significant risks, including harness-induced pathology (HIP), or orthostatic intolerance. This is a potentially life-threatening condition that rescuers and victims must be aware of. HIP occurs when the human body is held upright with restricted lower-body blood flow for an extended period, such as when a person is strapped into a harness.

The onset of symptoms can occur within just a few minutes, but usually takes at least 20 of free-hanging. Symptoms can include paleness, sweating, shortness of breath, blurred vision, dizziness, nausea, low blood pressure, and numbness in the legs.  

The mechanism behind suspension trauma is the pooling of blood in the lower extremities due to gravity and the restriction of blood flow by the leg straps of the harness, coupled with a lack of lower extremity movement.  All of these work together to reduce blood flow to the heart and brain. When blood flow to the brain is severely restricted, a person can experience syncope or fainting. Normally, when a person becomes syncopal, they fall to the ground, which is nature’s method of restoring that critical cerebral blood flow.  If, instead, the individual remains vertical after losing consciousness, such as when they’re suspended in a rescue harness, the continued lack of oxygen to the brain can lead to brain injury or even death. Uncorrected syncope can result in cerebral anoxia and can quickly become life-threatening.

As with most things, when it comes to HIP, an ounce of prevention is worth a pound of cure. To help mitigate the risks of HIP, rescuers who are hanging in harnesses for long periods should use their leg muscles frequently to pump blood back to the torso, such as by pushing against a rock ledge, using caving leg loops, or even simply shifting their weight from one leg strap to the other. Victims in the process of being rescued should be instructed to do the same.

If HIP has already taken hold and a rescuer or victim is beginning to demonstrate signs or symptoms, the most definitive means of relieving suspension trauma is immediate rescue and removal from the harness. If immediate rescue is impossible, raising the victim's legs to a sitting position can help, using equipment like a loop of rigging tape behind the knees.

Finally, rescuers must be vigilant in using proper personal protective equipment, including a well-fitted harness, to safeguard themselves and their victims during technical rope operations. Rigorous inspection, maintenance, and correct use of all safety gear are crucial to overcoming the many hazards of vertical rescue environments.