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What Are The Bends (Decompression Sickness) When Diving?

   December 5th, 2022   Posted In: Articles   Tags:

What Are the Bends When Scuba Diving?

SCUBA diving is a relatively safe sport. However, there is always a small chance of getting the bends. What are the bends and how can divers avoid getting them?

What Are the Bends in SCUBA Diving?

You may have heard the term before on TV or movies, but what exactly are the bends? The bends is the common term for what divers call decompression sickness. Decompression sickness, or DCS for short, is improper decompression after exposure to increased pressure. In diving, it is when small nitrogen bubbles become trapped inside the blood and body tissues due to a subsequent decrease in pressure.

What Is Decompression Sickness

In SCUBA diving, there are pressure changes that affect the gases a diver breathes. In most recreational diving circumstances, air is the source of gas that is inside a SCUBA tank. When you descend, the pressure increases and you absorb the oxygen and nitrogen inside the SCUBA tank. Oxygen is able to be used for metabolism, but nitrogen stays in your tissues and loads them with nitrogen that is unusable by your body.

The amount of nitrogen you can hold inside your tissues without getting the bends, is termed ‘no decompression limit’. If you exceed these time limits, the chance of getting the bends increases. Thus, longer and deeper dives have the greatest chance of getting decompression sickness. However, it is never 100% that you will or will not get the bends.

How Do Divers Get the Bends?

Besides absorbing more and more nitrogen while underwater, when you ascend from a dive, as the pressure begins to decrease, the nitrogen bubbles slowly dissipate out of your blood and tissues. It is very important to do a safe, slow ascent to help the nitrogen off-load properly. A rapid ascent increases the risk of getting the bends.

Lastly, doing a safety stop at 15 feet for 3 minutes will allow more time for nitrogen to leave your body and reduce your risk of getting the bends. Of course, there are technical divers, and divers that dive below 100 feet, that can dive safely by making several stops on the way up to allow nitrogen to escape the body.

What Are the Symptoms?

Symptoms of decompression sickness typically occur between 6-24 hours after diving. There can be several types of symptoms that arise from decompression sickness. Some of the main symptoms include:

  • Fatigue
  • Loss of appetite
  • Headache
  • Feeling ill
  • Pain in the joints
  • Coughing
  • Numbness
  • Tingling
  • Itchiness
  • Rash

When decompression sickness is severe (Type II), paralysis and death can occur.

How to Avoid the Bends

Complete avoidance of getting decompression sickness while diving is not possible. Most dive tables leave a 1% risk of getting the bends while diving. However, divers can mostly avoid the bends if they follow a couple of general rules:

1) Stay hydrated. Dehydration is a major cause of what causes decompression sickness when diving.

2) Never push your limits. Do not stay at a given depth for the maximum allowable bottom time. Instead, start to come shallower before there is less than 5 minutes remaining of no stop time.

3) Stay warm. Cold exposure is a significant source of decompression sickness risk because nitrogen does not release as quickly.

4) Ascend slowly. Ascending slowly from a dive will allow nitrogen to more easily come out of your tissues.

5) Make a safety stop. Safety stops allow for excess nitrogen to leave your body.

what are the bends

Risk Factors

There are many risk factors for what causes decompression sickness in SCUBA divers. 

1) Dehydration. As mentioned above, dehydration is one of the main causes of the bends.

2) Illness. If you are sick, not only will it be hard to clear your ears, but it also adds stress to your body and increases the risk of decompression sickness.

3) Being overweight. Nitrogen dissolves very readily in fatty tissues. So the more fat a diver has, the greater the amount of nitrogen that can be potentially absorbed.

4) Tired. Being tired puts extra stress on your body which increases the risk of getting decompression sickness. 

5) Alcohol. Alcohol that is usually still in the body from the night before can increase the risk of decompression sickness. Most often, it is the dehydrating effect of alcohol that causes this.

6) Over exertion. When you do strenuous exercise while diving, like swimming hard against a current, you can absorb more nitrogen.

7) Cold. Being cold on a dive can increase nitrogen absorption. Proper thermal protection is important to keep you warm while diving.

8) Injury. If you have an injury, blood flow tends to be altered slightly to allow perfusion of blood to the site of injury. This altered blood flow can increase risk of decompression sickness.

9) Heart Defects like patent foramen ovale.

10) Flying or going to altitude after diving. Follow the rules! After diving, it takes more time to get rid of the nitrogen still in your body. Researchers have found that after 1 single dive, you must wait 12 hours to fly and after more than 1 dive and several days of diving, you must wait at least 18 hours before flying. Even increases in altitude such as driving up a mountain can increase your chances of getting the bends.

11) Age. We can’t really doing anything about our age. It is always best to seek a doctor’s advice on whether it is safe to go diving. Usually, in older age, divers tend to make shorter, shallower dives.

Treatment for the Bends

Depending on the severity of decompression sickness, 100% oxygen can be all that is needed to help symptoms subside. However, oxygen therapy inside of a hyperbaric chamber is often what is needed. Anyone that experiences symptoms of decompression sickness after diving is advised to seek immediate medical help. More often than not, the chances of surviving decompression sickness with medical treatment are very high.

What are the bends and how do we avoid it are common questions in the dive community, especially for those just learning to dive. Most divers will never experience decompression sickness and will have safe dives throughout their careers. Just remember to follow the appropriate dive plans for your certification level, always stay well within your limits, and stay hydrated!

Candace is an avid scuba diver and freelance writer with a PhD in Biomedicine. She has been diving since 2002 and is currently a PADI IDC Staff Instructor. When she is not instructing, she enjoys writing about scuba and volunteering at the local aquarium where she dives with the sharks!

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