Decompression Sickness... What? How to React? How to Prevent?

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Decompression accidents are one of the most common diving accidents. Diving physician Catherine de Maeyer explains how a decompression accident can happen, what the symptoms are and how they are treated. but maybe even more importantly: what you as a diver can do yourself.

03-12-2015 -  by Kevin Van der Straeten


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Decompression accidents are one of the most common diving accidents. Diving physician Catherine de Maeyer explains how a decompression accident can happen, what the symptoms are and how they are treated. but maybe even more importantly: what you as a diver can do yourself.


Hi Catherine, welcome in our studio.  


Hi Kevin.  


Today we're going to talk about decompression accidents. But what is a decompression accident?  


Well, decompression illnesses or decompression accidents are caused by nitrogen bubbles. Decompression accidents are one of the big accidents or problems a diver can be confronted with, and have to be alert for. And so these deco-accidents are caused by nitrogen. Nitrogen is the most important gas in the air. The air that we breathe consists of approximately 80% nitrogen. And the rest is oxygen and carbon dioxide. But nitrogen is really the big part of the air that we breathe and is the cause of the decompression accident. And so if we start our dive, the ambient pressure or the hydrostatic pressure will rise, so the pressure of the air that we breathe will also rise. The amount of nitrogen that is offered to our body will rise as well. So we have a gradient from the air that we breathe towards our lungs, towards our tissues. So we take up a lot of nitrogen. And the deeper that we dive and the longer that we dive, the more nitrogen we absorb. Now when we stop the dive and we go up again, then we have this reverse gradient, which means that we will have to breathe away this nitrogen, we have to get rid of it. And so this de-saturation has to be done gradually, so that's the reason why we have to go up slowly and make decompression stops if necessary. And so that allows us to degas from the nitrogen. But in every dive small microbubbles of nitrogen are formed, and they travel around the body in the blood vessels. And if you de-saturate or decompress normally, these small bubbles will disappear. But if you go up too fast, then these bubbles can expand and they can block arteries, causing lack of oxygen and other products in the tissues, and that can cause the symptoms.  


And what are the results then? What are the symptoms?  


Well, it depends on the location of the bubble. For example, one of the smaller decompression accidents is extreme tiredness. You have done your dive, you're a bit tired. That's normal. But when you really feel like: "ah, I could sleep for 10 hours", that's not okay. So that could be seen as a light form of a decompression accident. The more familiar forms are the skin problems. The skin bends as they are called. This can be like blueish spots on the skin that can itch a lot or that can be painful. That's caused by small nitrogen bubbles that get blocked under the skin surface. Another kind of deco-accident are the bends. That's a nitrogen bubble that gets blocked in an articulation, like for example the shoulder or the hips or the knees. That causes a very unpleasant pain, a really deep pain. So that's a kind of deco-accident. And then there are the heavier forms. The more serious forms, like for example paraesthesia or paralysis, so no ability to move the legs or to move the arms. That's the heavy one, of course. Or the inner-ear decompression problem, where we can really have like a very heavy form of seasickness, when the organ that is responsible for the equilibrium is damaged. So it depends on the location where the bubble blocks...  


Okay, but you come to the surface, you start noticing some of the symptoms, what do you do?  


Well, most of the symptoms will happen in the first hour after the dive. Normally you don't get out of the water and then you have the symptoms. Most of the time it's after half an hour or an hour. And then when you notice the symptoms... The first thing it that you have to notice them. A lot of divers know it from their textbook, but when it happens to themselves they're not familiar with it. Then it's important that you breathe 100% oxygen, because you will oxygenate the tissues that can get damaged, and you will force your body to get rid of the nitrogen, because when you breathe only oxygen, there's no nitrogen and you can pull the nitrogen out of the body. And then the second thing is: allow the diver to drink, if it's safe. And you have to go to a hospital or a unit where hyperbaric medicine like a caisson can be offered. When you are the caisson, you do a dry dive, so you get underpressure again. And then the bubble will then get smaller and that way you can exhale it and get rid of it. So three important things.  


Some divers always say: "well, if you have the symptoms, then you need pressure again so just go down again". Is that a good idea?  


I wouldn't do that. I know it's explained in the textbooks and of course in theory it's a good way to get rid of the bubbles. But the problem is that a decompression accident can get worse. It can start with a small problem, but it can really become like a paralyzed like or so and that happens very, very quickly. In 10 minutes or so. And you can become completely paralyzed. And you don't want that to happen under water. So really, if possible: 100% oxygen, that's very important. And then go to the hospital, where they can help you.  


Catherine, thank you very much for coming over.  


You're welcome.  


And you at home: thank you for watching our show. I hope to see you next time!


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