A discussion on the use of safety harnesses, the benefits of the harness, and analysis of suspension trauma
Three hundred feet in the air, stepping from girder to girder, the last thing I want running through my head is a question regarding the safety equipment I am using. Will the fundamental design of that equipment in fact save my life, or will it actually take it from me? Will I be home watching the ballgame with my family tonight, or will they be preparing for my funeral? Yet these are the questions that are quickly becoming an issue as many workers who are required to wear full-body harnesses have become aware of an article that implies the current design of full body harnesses will, in fact, kill you. But is this fact or fiction?
That article, “Will Your Safety Harness Kill You?” (published on page 86 of the March 2003 Occupational Health & Safety), is loosely based upon the findings of the research document “Harness Suspension: Review and Evaluation of Existing Information” (Sedon, 2002) commissioned by the HSE (Health and Safety Executive) in Europe and published by HSE Books (ISBN 0 7176 2526 5). Both the article in question and the HSE reports expound on the issue of Suspension Trauma.
Suspension trauma, also known as harness induced pathology, is well documented and has been an issue of study since the late 1960s. In its simplest form, suspension trauma is where the body is at rest in a vertical state with the lower body motionless, and as such, blood begins to pool in the lower extremities because the muscles in the legs are not contracting on the veins and helping the blood back to the heart (against gravity). Blood is not properly circulated, the individual’s blood pressure drops, the brain does not receive adequate blood flow, and unconsciousness follows. In contrast, when an individual collapses, the pooled blood is now no longer being held down by gravity and it returns to the heart, where it is once again distributed to the body.
This is a simplistic explanation of a very complex medical condition. When an individual hangs in a harness in a vertical or near-vertical position without moving his legs, the same thing can happen, only this time when he passes out he remains vertical, and death is imminent if he is not quickly brought down. (For a detailed review of suspension trauma and related research, see the HSE report that is available in PDF format from the HSE Web site, www.hse.gov.uk.)
Real Fall Incidents Are Different
That suspension trauma exists is not a question, but whether your safety harness will kill you does bear some very serious discussion. Within the HSE report, several studies are discussed, all determining suspension times and evaluating the physiological impact of suspension on the body. It is important to note that in each of these studies, the participants are directed to remain absolutely still, representing an unconscious worker.
In a real fall situation and unless the worker is hurt during the fall, the likelihood of his being unconscious and subsequently motionless is very slim. His struggling will to a certain degree delay the suspension trauma (keeping his legs moving and helping to move the blood), subsequently increasing the possible suspension time and opportunity for rescue. (Remember, the core basis of suspension trauma is the immobility of the worker where the leg’s muscles are not working to counter the effects of gravity.)
In 2000, four workers were suspended for more than an hour as a result of a scaffolding collapse on the Ambassador Bridge linking Windsor , Ontario to Detroit , Mich. When they were successfully rescued, they were all in good health and were not suffering from suspension trauma. The number of stories of workers who walk away from falls with full-body harnesses far outweigh the few stories of suspension trauma when using a full-body harness with rear dorsal “D” ring. Interestingly, it would seem that suspension trauma incidents appear to be more prevalent in rescue training where the healthy training casualty feigns unconsciousness, hanging limply--only to suddenly pass out and become a real victim. Again, the lack of movement is perhaps more an issue than the mode of suspension.
It is perhaps a lack of knowledge of the subject that allows workers to put themselves into that risky position. That the trauma itself comes on so quickly, with minimal warning, also could explain why a perfectly healthy and aware individual may be so suddenly overcome. We must again come back to the basic question, “Will your safety harness kill you?” P erhaps our problem is not the harness, but our attitude toward fall arrest equipment.
Influence of the Wearer's Attitude
What does attitude have to do with a harness? If I see my harness as a tool of my trade, I will be more inclined to take better care and attention in my choice of harness, how well I maintain it, how my harness fits me, and how I adjust it for both wearability and, more importantly, tolerable suspension. Choosing your harness must be a personal process; a worker should fit the harness for his body and then be briefly suspended to ensure the harness is comfortable. (It is important to remember this suspension is under a controlled, safe environment and should only be maintained for a very brief time.)
The ability to adjust the various straps on a harness properly becomes critical to the harness's performance. Sizing is an often overlooked piece of the puzzle, too. Harnesses often are purchased based upon the "universal" sizing; that one size fits most (not all). By this thinking, a harness of the same size and style is given to a 5-foot, 4-inch, 140-pound worker as to a 6-foot, 290-pound worker.
While the harness may appear to adjust properly and not seem to be a problem during normal work activities, it will feel very different during a fall. Sizing is critical to ensuring that the “D” ring, buckles, and chest strap are all positioned in the right places, minimizing the possibility of injury and maximizing the suspension time. Even the design of the harness (vest style versus crossover) will affect the fit and function for different body types.
A true crossover (“X”) design will fit women and thin or smaller (5 feet, 7 inches and shorter) body types much better because it forms the harness to the body, bringing the webbing into the body’s center of mass. Where you have a body with more mass, especially in the stomach area, a vest style is more appropriate and allows the harness to be properly adjusted for both working and fall protection.
As a tradesperson will learn to properly utilize his power and hand tools, so must he learn to use his fall protection tools. Training is an essential key to changing the attitudes of individuals working at height. Education must include the proper application, donning/doffing, fit, and suspension in harnesses. It also must include what to do when you are suspended so that you can maximize your tolerable suspension--moving the legs, raising knees into the body (difficult, yes, hanging from the back “D” ring, but essential to keeping the blood moving through the body).
New products and techniques must be considered so we can effectively deal with the different stages of fall protection. Most studies, including the HSE report, detail the different requirements for subsequent stages of fall protection. It can be shown through research (as presented by Amphoux, 1983, in a presentation entitled "Exposure of human body in falling accidents," Toronto, Canada) that the most desirable point for the fall and subsequent impact of stopping that fall is the dorsal “D” ring located between the shoulder blades.
This research supports the choice of the standards bodies of North America to utilize the dorsal “D” ring as the required connection point for fall arrest. CSA, t he Canadian Standards Association, even goes farther. CSA Z259.10 M90 section A5 identifies the best solution for a fall arrest as a body holding device but also identifies the risks associated with that choice. Educating the worker to the risks associated with the job and tools is always critical. Product manufacturers must start to develop products that will deal with getting workers from a near-vertical position (best for fall arrest) to a near-horizontal or at least seated position (best for suspension). As a minimum, we need to look at ways to provide the conscious worker with some tool that allows him to stand and work the leg muscles (maintaining blood flow).
Implications for Rescue and Response Times
Without question, the renewed interest in suspension trauma has highlighted a need for better rescue and rescue response times. With or without the implications of an unconscious worker, a rescue plan must be in place and able to be initiated immediately upon a worker falling. Workers must never work at height alone so that the plan can be immediately activated; a lone worker cannot initiate a plan for his rescue if he is hurt or unable to reach a means of communication.
Rescue must be initiated by reaching the worker and getting, at the very least, a loop strap to the worker so he can stand and take some of the pressure off his harness and move the muscles in his legs. Where possible, rescue devices should be implemented so the worker can be moved into a less vertical position; however, it is critical that where a worker is or even may be experiencing the effects of suspension trauma, he must not be laid horizontal. By laying the worker horizontal, the pooled blood causing the trauma will now rush to the heart and may, in essence, overload it, causing massive damage to the ventricle and potentially resulting in imminent death. Rescue must be practiced on a regular basis so workers can effect a safe and efficient rescue within a very short time (15 minutes maximum).
The Challenge for Safety Managers
As professionals within the fall protection industry, our challenge--no, our responsibility--is to mitigate, reduce, and wherever and whenever possible, to eliminate the risk associated with working at heights. Our first question should always be, “Can I do the job differently? Can I design out the need to go to height?” If we can’t design out the risk, then we must reduce and/or eliminate the risk of a fall through prevention (guardrails, restraints), leaving our last choice as fall arrest.
If fall arrest is the choice, then we must take the responsibility of making the right choice for equipment, ensuring it fits and works for the individuals using it. We must train those workers on not only the how to’s of fall protection, but also the why’s. Finally, if we are going to put our workers at risk, then we must have a plan to get them down safely and efficiently within a limited amount of time (no more than 15 minutes, though most recommendations are becoming five minutes). Rescue must be a part of our total fall protection plan.
Within our industry, resistance to change is without question our greatest challenge. Suspension trauma is not a new concept, just one risk of many associated with working at height. To blame the harness is systematic of a society that wants to find a quick-fix solution. Just as a saw, a drill, a wrench, hammer, or any other tool can be used improperly, so can a harness. I would rather bet my life--and I do on a regular basis--that when used properly, my harness will save my life. [OHS endbug]
Emmett McGregor is a master trainer and Director of Business Development for the training and consulting division of DBI/SALA, a Capital Safety Group Company located in Red Wing, Minn. DBI/SALA Training and Consulting provides a full range of fall protection and industrial rescue training programs ranging from four-hour awareness to 40-hour competent and qualified person courses. For more information, call 800-328-6146, ext. 690, or visit www.salagroup.com
1. Harness Suspension: Review and Evaluation of Existing Information, (Sedon, 2002).
2. Suspension Trauma? Who is at Risk, John Greenfield.
3. Suspension Trauma--Serious Risk to Subject, Robert Thomas, Sept. 27, 1999 , in a post to the firstname.lastname@example.org list.