Why is Decompression Sickness Called ‘The Bends’?

why is decompression sickness called the bends

If you’re just starting out with scuba diving, you may have overheard some other divers talk about ‘the bends’, but aren’t sure exactly what that means. As unsuspecting as this term is, it is actually referring to a dangerous condition scuba divers sometimes experience known as decompression sickness (DCS). How come such a dangerous ailment such as DCS is known by such a harmless sounding name? To answer this question, we will need to first go over the history of the term.

When Did ‘The Bends’ First Catch On?

It’s hard to pinpoint the exact origins of this term. However, since the bends describe the common symptoms one exhibits when afflicted with decompression sickness, we can estimate that it had to occur around a time when DCS was frequent and well-known.

Before scuba diving was as common as it is now, the earliest iteration of large scale scuba diving using compressed air was done during the construction of the Brooklyn bridge in 1871. Back then, the gear was very primitive and the lack of safety standards would give OSHA a heart attack. Workers were lowered into the riverbed in a diving bell where they dug the foundations for much of New York City.

These workers, known as sandhogs, were lifted up to atmospheric pressure without any decompression stops. Once they reached the surface, they immediately suffered from decompression sickness, causing their joints to “bend” out of shape. This is perhaps when the term started to catch on, and the effects of DCS started to get researched.

What is Decompression Sickness?

Nowadays, we understand DCS and the bends much more than those poor workers did in the late 1800s. When one is afflicted with DCS, a common symptom is reduced joint mobility caused by gas bubbles forming in the body. These bubbles typically accumulate in the joints, limiting mobility and giving them a bent appearance.

Where did these bubbles come from? They are dissolved gases that appear when one ascends rapidly and is not given enough decompression time. These bubbles can seriously damage the body. For instance, they often cause arteries and veins to constrict and wrap around a lot of corners. This is why joints are often bent and movement is restricted for individuals affected by it.

Long-Term Effects of Decompression Sickness

DCS is not exclusive to scuba divers; freedivers and people at high altitudes can experience it as well. The reason why it is most commonly associated with scuba divers is because prolonged inhalation of compressed gases easily causes DCS. If you experience the following symptoms, there is a possibility that you are suffering from decompression sickness. They are:

  • Local joint pain (often in shoulders, elbows, wrists, hips, knees, and ankles)
  • Weakness in the arms and legs
  • Headache
  • Nausea
  • Difficulty thinking clearly
  • Numbness & tingling
  • Extreme fatigue

Decompression sickness can cause serious long-term effects on the body. Even mild cases of decompression sickness should be treated. If left untreated, decompression sickness can lead to muscle weakness, permanent neurological damage, difficulty controlling the bowels and urinary function, and chronic joint pain. The neurological damage can result in brain and spinal cord damage from the gases bubbling in those areas. The damage is often permanent. In severe cases, it can even lead to death.

Why Do Scuba Divers Commonly Experience The Bends?

To answer this, we have to first understand how air works on land and how it works underwater. The air we breathe typically consists of 21% oxygen and 79% nitrogen. However, additional air can be dissolved into our body if we spend a prolonged period of time at high altitudes, or by breathing compressed gas via a scuba tank and regulator.

By breathing these higher pressures of air, our blood and tissues will absorb more air up until the point where the dissolved gases and surrounding gases reach equilibrium. At 20m (66ft) underwater, our body is subjected to 3 atmospheres of pressure. It does not actually harm us to breathe in this highly compressed air. The damage is done when a diver surfaces rapidly, and the dissolved gases leave the blood and tissues too quickly, resulting in the bends.

This occurs because gas diffuses out of our body when we go to a lower pressure environment. There is a limit to how much gas can leave the body before it becomes harmful. That is why the deeper and longer you dive, the more likely you will experience the bends, unless you perform the necessary prevention methods to safely ascend.

How to Avoid the Bends

Now that we know a little bit about the bends and why it happens, what are the steps we can take to avoid these symptoms? Thankfully, it is not that hard to prevent decompression sickness and its symptoms, at least for recreational diving. In fact, as part of the scuba certification process, the instructors will hammer into you the steps you need to take to reduce the risks of getting DCS.

What you need to do is to ascend slowly, stay within the No-Decompression limits (NDL) and perform safety stops every dive. You can calculate your NDL using a dive table, however most divers nowadays simply use a dive computer to do all of the calculations for them. A reliable dive computer will warn you if you are ascending too quickly, when you should perform a safety stop, how many stops you should take, and so on.

Furthermore, you should be in good physical health and be well-hydrated for a dive. Know your body’s limits and stay within it. A conservative diver is one that will enjoy many decades of diving; a reckless diver will one day meet a watery end.

If you are a new diver, you are not necessarily more at risk of experiencing the bends, nor is a veteran diver necessarily more resistant to it. With that said, new divers are more susceptible to the bends because of their nervousness and lack of experience which causes them to make mistakes. For instance, if they lose track of time and find themselves low on air, they may make a hasty ascent. Anxiety will trigger a fight or flight response, and staying calm is critical to prevent any reckless decisions from being made.

If you’re worried about running out of air, then perhaps you should have a reserve air tank for situations like this.

Parting Words

So why is decompression sickness called ‘the bends’? The bends is actually describing the symptoms of decompression sickness, but more often than not it does mean the diver has contracted it as well. It is a slang term that was used in the late 1800s that stuck to this day. The bends describes the bend in people’s joints where the dissolved gas bubbles accumulate, restricting their mobility and giving the joints a bent appearance. The image is quite visceral, which probably helped the term persevere over the centuries as it is an apt description of a serious problem.