Suspension Trauma: The Danger of Fall Arrest Systems

A construction workers falls off the edge of a tall, partially built structure. They plummet six feet, but thankfully they don’t make contact with the ground.

Instead, their fall arrest system kicks into gear. The line locks. The anchor point holds steady. The worker stays securely attached in their harness.

The fall protection planning worked – the worker’s fall has been successfully arrested.

But just because they haven’t hit the ground, it doesn’t mean they’re safe. Not yet.

That worker is still suspended in mid-air, which means they’ll suffer from suspension trauma if they don’t come down soon. And the effects could be serious.

Fall Hazards in Construction

According to the Bureau of Labor Statistics (BLS), the construction industry accounts for almost 20% of all workplace fatalities. Of these fatalities, nearly 40% are due to falls, slips, and trips – almost all of which are falls to a lower level.

The construction industry is also responsible for a disproportionate percentage of all fatal falls. Specifically, 47.4% of them in 2022.

Since falls are such a prominent and often fatal hazard in the construction industry, it’s no surprise that fall protection equipment is considered a crucial hazard control measure on any construction site.

However, while fall arrest systems are essential for preventing injuries from falls, they can introduce their own dangers, like suspension trauma.

What Is Suspension Trauma?

Suspension trauma is a condition that sets in when a worker remains suspended in their fall protection harness for an extended period of time.

It’s also known as harness-induced pathology, orthostatic shock, and orthostatic intolerance.

The Physiological Effects of Prolonged Suspension

There are many physiological factors that could lead to suspension trauma. Unfortunately, studies have not been able to agree on a single, specific causal explanation.

These are the three most prominent theories (and a combination of these causes is also possible):

• Low cardiac output as a result of blood pooling in the lower extremities
• The accumulation of metabolic waste in the blood and organs in response to the lack of available oxygen in the circulatory system
• Harnesses with a dorsal connection may cause compression to the arteries and femoral veins (an effect that is less less severe in harnesses with a ventral connection)

The heart is a pump. It receives oxygen-rich blood from the lungs and sends it to the rest of the body through the arteries. This is how organs receive the oxygen they need to produce energy and function. The heart then pumps the deoxygenated blood back to the lungs where it releases carbon dioxide (a waste product) and takes in fresh oxygen. Then the cycle starts over again

During suspension, the veins and muscles in the pelvic and femoral area are compressed, which impedes blood flow. This causes the blood to pool in the legs instead of completing the proper circulation throughout the body. The blood in the legs then loses its oxygen and becomes loaded with metabolic waste product (like the CO₂ it would normally expel through the lungs).

The upper body also suffers. With most of the blood moving to the legs, the brain, heart, and other organs can’t get the blood and oxygen they need to function properly.

Older studies have suggested that the lactic acid buildup in the legs during suspension (another physiological response to lack of oxygen in the circulatory system) could lead to renal or heart failure. However, more recent research found that, while slightly acidic blood could affect the heart’s contractility in the short term, it won’t affect the heart’s rhythm and, therefore, won’t induce sudden death.

Is Suspension Trauma Deadly?

Many articles on suspension trauma warn of its deadly consequences. And given all the physiological effects associated with it, it would seem like a foregone conclusion that anyone experiencing suspension trauma for an extended length of time will lose their life to it.

However, a literature review published in 2023 found that suspension trauma is a rare occurrence. And as such, fatalities from suspension trauma are exceedingly rare. In fact, International Rope Access Trade Association (IRATA) technicians logged over 5.8 million hours on rope over the span of 11 years without a single case of suspension trauma.

How the Concept of Suspension Trauma Took Off

Suspension trauma was first studied in climbers, not on construction sites.

The first research on suspension trauma was conducted in 1970 and studied 10 climbing fatalities. The victims were suspended in their harnesses for time spans that ranged from 90 minutes to 8 hours. Eight of these climbers were rescued, but all died as a result of the incident, surviving between 30 minutes and 11 days after their rescue.

Another study from 1972 indicated that 10 out of 23 climbers died after a fall and suspension in a harness, despite having no other apparent injuries. Subsequent tests indicated that the subjects lost consciousness after hanging in a harness between 6 and 30 minutes.

Suspension Fatalities in Industrial Settings

Despite the common worries about suspension trauma fatalities, there isn’t much verifiable data about their occurrence in industrial environments. I was unable to find objective reports of such fatalities, and the same study mentioned earlier, along with a few others, also came up empty.

There are, in fact, very few studies or scholarly articles on suspension trauma fatalities. This is itself an indication that there isn’t enough evidence of such workplace fatalities to warrant investing in research on the subject.

Construction Harnesses and Suspension Trauma

Due to its possible negative impact on human health, there have not been many studies on suspension trauma. The ones that have been conducted were stopped early to ensure the safety of the participants. Because of this, our knowledge of the extremes of suspension trauma and its potential for fatality has been more or less based on educated guesses and incomplete data.

Although scarce, the data we do have seems to agree that the standard construction harness with dorsal D-ring attachment is the most conducive to suspension trauma. Placing the D-ring at the back of the harness, rather than the front, is more likely to induce suspension trauma in the event of a fall.

This seems to be due to the position in which the body hangs when suspended from the back. The dorsal D-ring “pushes” the body forward, which:

• Causes compression in the chest area, which further inhibits blood circulation and respiration
• Concentrates most of the pressure over the pelvic area
• Makes it harder to push against a wall (one of the recommendations for delaying suspension trauma)

OSHA Recommendations for Suspension Trauma

OSHA’s Information Bulletin on suspension trauma states that loss of consciousness and subsequent death can occur after hanging in a harness for less than 30 minutes. Despite the lack of workplace fatalities to reference, the evidence from earlier studies shows that this timeline is at least possible.

This 30-minute window has been interpreted by many employers and safety professionals as a requirement to rescue suspended workers within 30 minutes of a fall. However, OSHA’s 1910.140(c)(21) only stipulates that “The employer must provide for prompt rescue of each employee in the event of a fall.” The standard doesn’t impose any time limit on executing the rescue.

Furthermore, a 2004 letter of interpretation clearly states that “OSHA standards do not provide specifically for a maximum allowable time to remain suspended in a harness following a fall event.”

So, OSHA requires the rescue to be prompt. Exactly how prompt isn’t stipulated.

Risk Factors for Suspension Trauma

The few studies on suspension trauma have demonstrated that anybody hanging in a harness can suffer adverse effects from it. But there’s an important distinction to be made. After all, window washers, linemen, and arborists can spend a big part of their working lives hanging in harnesses, yet their risk of suspension trauma is negligible.

Suspension trauma, then, is a much more likely to occur after a fall.

There are several reasons for this:

• Harness Type: When employers know their employees will be hanging for most of the day, they tend to invest in high-quality harnesses that have additional support and better positioning. The harnesses used for fall arrest systems generally don’t have these features.
• Harness Use: Workers whose jobs are done while suspended use their harnesses for work positioning or sit in a bosun chair. This limits the pressure exerted on the pelvic and femoral vein area, which significantly reduces the risk of suspension trauma.
• Positioning: Workers in a suspension system are in full control over their positioning, so they can easily move their legs to activate the muscle pumps in their lower extremities. This allows them to maintain a healthy circulation, which is a major factor in suspension trauma.

Because of this, suspension trauma is more likely to affect employees who use harnesses strictly for fall protection. These workers include:

• Roofers
• Framers
• Scaffolders
• Oil rig workers
• Steelworkers
• Wind turbine technicians

Preventing Suspension Trauma

Keeping workers from falling is by far the best way to prevent suspension trauma. After all, there can’t be any suspension trauma if there isn’t any suspension. But if all the fall prevention systems fail and a fall does occur, what’s the best way to minimize the adverse outcomes? Here are a few key factors.

Better Fall Arrest Harnesses

If a dorsal D-ring can safely be substituted with a ventral ring harness, the effects of suspension trauma will be minimized.

Even when this isn’t possible, harnesses with more support and padding are preferable to plain web harnesses.

Trauma Straps

Trauma straps also allow a suspended worker to get themselves in a partially standing position, which improves circulation and reduces the risk of suspension trauma. These are very common, affordable, and effective. A single strap is typical, but two straps will provide greater comfort and better stability.

Here’s how trauma straps should be used:

• Attach the Straps: Secure the trauma straps to the harness (according to the manufacturer’s instructions). The straps are typically attached to the leg loops of the harness so they’re more accessible.
• Practice Using the Straps: Before trauma straps are needed in a real-world situation, every worker should get to try them out in a controlled environment. Using a tripod or some other means of suspension can create a scenario where the straps can be used without placing anyone at risk. Getting hands-on practice with the straps can save valuable time if and when a fall does occur.
• Adjust the Straps: The length of the straps can be adjusted during suspension, if needed. If the pressure isn’t relieved when stepping into the straps, it’s a good indication that it needs to be shortened.

Onsite Work Equipment

Keeping fall rescue equipment on site is essential for shortening the response time and minimizing how long an employee remains suspended in their harness.

Depending on the scope of work, this equipment could include:

• A ladder to reach a fallen worker and allow them to relieve harness pressure by stepping on it
• Aerial work platforms or crane-support personnel baskets

Self-rescue with ascenders or descenders is also possible, though not feasible with dorsal D-ring harnesses.

Training

Training ensures that workers are aware of the risks of working at heights, know how to minimize them, and have a good sense of what to do in the event of a fall.

In-person training led by an instructor that combines theory with hands-on practice is preferable to online modules. The training should consider the equipment available, the work itself, and the specifics of the site.

Comprehensive fall protection training will cover what should be done before falls occur and what to do after a fall has taken place.

Before the Fall

Workers should know how to select the proper equipment, don it, and adjust it to minimize discomfort.

When the harness is properly adjusted:

• The dorsal D-ring should sit between the shoulder blades
• The chest strap should be tight enough to allow comfortable breathing and movement
• The chest strap should be closed across the chest (too low and it could lead to rib injuries; too high and it could impact the neck and face during a fall)
• The legs must be adjusted so they’re not too loose – otherwise, the entire harness will slip up, placing the chest strap and D-ring in dangerous positions

After the Fall

Workers should know the steps to take after a fall has occurred:

• How to use the trauma straps, including how to attach them to the harness and adjust them
• How to adjust the position of the body to delay the onset of suspension trauma (although this is only possible with certain types of construction harnesses)
• Tricks to relieve pressure without trauma straps (like lifting the legs, making a loop around the feet with the rope to serve as an improvised strap)
• Slowly and continually moving the legs to encourage healthy circulation (if a structure is close enough, pushing on it is a good way to promote blood flow)
• Calling for help as soon as the fall occurs (if working out of sight of other workers, employees should keep a phone or radio on them in an area that won’t be affected by the fall and will be accessible while suspended)

Suspension Trauma Rescue

OSHA doesn’t have a standard dedicated solely to rescuing workers who have fallen and are hanging in a harness. However, OSHA’s 1926.502(d)(20) (for construction) and 1910.140(c)(21) (for general industry) state that employers must implement plans for a prompt rescue. Since a specific timeline isn’t provided, it’s up to the employer to determine what “prompt” means.

OSHA warns that suspension in a fall arrest device can result in unconsciousness and death in under 30 minutes. But studies have shown that some symptoms can appear in a matter of minutes, with some subjects losing consciousness after only six minutes of suspension.

Given this, the rescue should be executed within a few minutes of a fall.

There isn’t much guidance on how the rescue should be performed, either. This is probably because working at heights is so varied and it would be difficult to draft a standard that fits every scenario.

We can, however, run through a few types of fall suspension rescue and what each of them involve.

Self-Rescue

A self-rescue involves the fallen worker using their equipment and skill to free themselves from the suspended position. This method is often the quickest and safest option, especially if the worker is only slightly suspended.

However, there are some conditions that have to be met before designating self-rescue as the primary way of extracting a hanging worker:

• The worker must be trained in self-rescue techniques
• The worker must have all the equipment needed for a self-rescue on them
• The harness and other equipment used must be designed for self-rescue (or at least deemed suitable for it)
• The worker should have the physical strength and coordination required to execute the rescue

A major limitation of self-rescue is that it can no longer be performed if the worker is injured by the fall or loses consciousness while suspended. Because of this, there should always been a redundancy plan in place.

Assisted Rescue

An assisted rescue is often necessary when the worker is unable to perform a self-rescue due to injury, exhaustion, or the equipment used.

It can also be required when the height of the fall is significant.

This type of rescue relies on co-workers who can help the suspended worker extricate themselves. It also requires equipment that must be available on the site. It is generally performed with equipment that other team members are already using, such as ladders and aerial work platforms.

There are a few limitations of this method:

• Workers performing the rescue must have adequate training for working at heights and using the rescue equipment.
• The equipment must be available onsite and be capable of reaching all areas where a worker could potentially fall and hang.
• The rescuers should have the physical strength and coordination needed to safely assist the suspended worker.

Professional Rescue

A professional rescue is often necessary for extreme heights, hazardous environments, or when the fallen worker is seriously injured.

This method involves a fully trained and equipped rescue team, such as firefighters or specialized rescue personnel. While the expertise and specialized equipment involved makes this a desirable option, waiting for the team to arrive at the site can delay the rescue. To be successful, the rescue team must either be on standby or located very close to the jobsite.

Another possible limitation is that the rescue team may not be familiar with the particulars of the working environment and may not be equipped for all possible scenarios.

After the Fall: Post-Rescue Care

Regardless of the work environment or type of rescue, it’s a good idea to call 9-1-1 as soon as the worker falls. Medical responders might arrive at the site before the worker is lowered to the ground and can take over from there.

For a long time, the common advice was to keep the worker in a seated position (at 30 to 40 degrees) and very slowly (over the course of 30 to 45 minutes) lay the worker down into a horizontal position. The idea was to avoid letting the blood rush back to the heart too suddenly, especially since the blood might have a higher acidity level due to the buildup of lactic acid and other metabolic byproducts.

However, other research has noted that the prolonged seated position is not necessary to prevent harm and that the acidification of the blood is not significant enough to damage the heart. Instead, it advises returning the worker to a horizontal position to re-establish proper circulation and oxygenation of the blood, which are the most important factors for a successful recovery. In fact, this approximates the body’s natural response of inducing fainting to encourage a horizontal position.

Given this conflicting advice, most fall protection advocates recommend getting first responders involved. That way, decisions about how to treat the rescued worker and how to position their body can be left to medical professionals.

Conclusion

Suspension trauma is a topic that is often discussed but not well understood. A lot of the training and practice surrounding it is based mostly on expert opinion with little empirical evidence to back it up.

One thing we do know with certainty, however, is that being suspended in a harness for even a short period of time can have adverse health effects. Despite a lack of documented fatalities due to suspension trauma in industrial environments, the potential for the loss of life still exists, especially when taking other factors into consideration (like the possibility of fainting or an injury).

As such, employers must have a detailed rescue plan in place to extricate workers hanging in a harness after a fall – and to extricate them quickly.