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Ssssshhhhh…. Decompression sickness

written by Lee Johnson – Perth Scuba Managing Director

Do they call them silent bubbles because when someone gets decompression sickness – no one talks about it?Bubbles

It happens… Trust me, I know – Not from my own personal experience, but by the experiences of others.

What actually happens when you get the bends? Is it something we should hide?

Recently in the store, I got into explaining to my staff, the physiology of diving – I know weird right? And you just thought we talked about the girls and the last dive trip we went on and all that cool stuff! Anyway, I was talking about how nitrogen works and micro bubbles and how the body works with it all when we dive. At the end of the chat a couple of my staff came up and said “wow – I have dived for years and never knew that. I have never had it explained to me so I understand what actually happens” I got to thinking that if we don’t explain these things to our professional level guys, how are non professional divers meant to understand? Don’t get me wrong, my staff are full bottle on diving within limits and avoiding decompression diving unless trained to do so, and the guys who are trained to do so are all over it, but having it explained I guess in layman terms is what seems to have been lost somewhere. So here we are… I figured that I can do a couple of things about it. I can write here and put it out there for you all to read and hopefully understand, and if that saves 1 person from getting bent or taking risks that could end up that way then mission accomplished. OR I could leave it unsaid and never know if I could have helped someone who didn’t know. Whatever the case, I figure it’s worth a shot… So here goes – and please – I am sure there is a lot more science involved in this and I am sure that there is a lot more medically that I am not putting in here – but I am writing this as it is best explained to someone who just doesn’t quite understand.

So here we go:

When we breath air, we inhale 21% Oxygen, 78% Nitrogen and 1% other gases (a mixture).Composition of Air

Our body absorbs the oxygen and nitrogen from the air and pushes the nitrogen out of the body through a combination of the exhaled breath and by releasing nitrogen through our body – (pores) in the form of very minute gas particles. This keeps the body free of Nitrogen build up.

When we dive, we enter an atmosphere much denser than air. What this means is that whilst we can expel nitrogen through the normal exhale, it reduces the bodies efficiency in removing consumed nitrogen through the skin. The deeper we go, the harder it is for nitrogen to escape. This added to the fact that when we dive deeper, our partial pressures change and the amount of nitrogen consumed is much higher again. The longer the dive, the more nitrogen is absorbed and the less nitrogen is able to escape through our skin due to the density of the water.

When we ascend, the pressure on our body is reduced. When we get to the last 5 metres our bodies are able to off gas the excess build up of nitrogen much more efficiently than at depth. This is why we do decompression stops and safety stops at shallower depths.

You will never be able to fully flush out all of the nitrogen absorbed, but you can certainly bring those levels down to much safer levels in a very short time.

So what happens when we get bent?

The nitrogen is transferred around your body in your blood in the form of minute bubbles by cells called hemoglobin. Hemoglobin carries oxygen around the body too so they are very important cells.

When we ascend gases expand. This includes all of the tiny micro bubbles of nitrogen that are now effectively trapped in your bloodstream unable to escape because of the density of the water and the pressure asserted on your body. These nitrogen micro bubbles continue moving around your body until they can be dispersed through the skin. If the ascent is too fast for the micro bubbles to escape through the skin, they become too big. Once they become too big to escape through the pores, they continue moving around the body until they become stuck, usually in a joint or area with blood flow restrictions. Once they get stuck, additional micro bubbles get stuck in the same area trapping the flow through that area. This makes the joints very stiff and can lead to the body contorting making it look like your body is bent up (This is where the name “the bends” comes from).

When this happens the only way to fix the problem is to take the body back to the depth where these micro bubbles became too big and force them back into solution (so small they are free to move around the body again). Then coming up at the correct speed with plenty of time allowed to slowly release the micro bubbles allows the nitrogen to escape the body effectively removing the bend. Traditionally, the only way to do this is in a controlled environment in a recompression chamber. (“Recompression” because you are recompressing the micro bubbles to a size where your body can remove them naturally) 100% Oxygen is also used in the assistance of diluting the nitrogen to a smaller percentage while giving your body the necessary boost to begin repairing the damage caused by nitrogen “scarring”.

Decompression Sickness can affect different people in different ways. There are a bunch of different types of decompression sickness too from skin bends to lymphatic bends and a whole bunch of nasties in between. The thing with decompression sickness is that any one person can be affected differently and the nitrogen build up can be anywhere in the body. Some cases of decompression sickness can end up with dire consequences, paralysis, blindness or even death. It all depends on where those tiny micro bubbles get stuck. The best way to avoid any of this – is to take the most precautions as possible.

So we now know how it all happens, how do we make sure that it doesn’t happen to us?

This is a very open ended question because I have seen some things done by divers which left me amazed that the diver who did it – didn’t end up in the chamber, and then I have seen people dive “safe” dive profiles and still get a mild bend.

If you speak to a hyperbaric doctor or nurse, they will all tell you that a safe profile is one where you don’t end up visiting them, thus the open ended question of how do you prevent it.

So here goes a list of things you can do to assist in the prevention of DCS (Decompression Sickness).

Physical Preparation:PADI Recreational Dive Tables

  1. Stay fit – no you don’t have to hit the treadmill and exercise bike – but if it’s been a while between dives, make it a short and shallow one first.
  2. Drink a lot of water – Prior to the dive and after the dive. Hydration is VERY important.
  3. Make sure you are 100% healthy before a dive. Don’t dive hung over, don’t dive super tired, and don’t dive if you just don’t feel right. Yes even if you just spent $130 on a boat trip or you have just landed on that overseas dive holiday you have been planning for a year. Rule of thumb… if you don’t feel 100% then you probably aren’t… put off the dive until you do feel 100%
  4. Drink a lot of water – I know I said that already but I can’t emphasize that enough.
  5. If you have taken recreational drugs, DON’T DIVE. These drugs usually give you a high by increasing your heart rate – something we definitely don’t want to do in relation to nitrogen transfer around the body. (Avoid drugs and diving altogether).

On the dive:

  1. Don’t over exert yourself.
  2. If you dive with a dive computer – set it to the most conservative setting – The Hyperbaric docs tell us that even that in some cases is not enough.
  3. If you are diving with a computer, don’t assume that you are fine. Dive computers are designed to give information to assist you in your dive calculations. Whilst better than a guess – they still have a whole bunch of parameters which they cannot calculate – such as your weight, fitness and external dive conditions.
  4. Plan your dive and stick to your plan.
  5. Make the deepest part of your dive the earliest part – don’t go and check out the sand eels at 30 metres at the end of the dive which has been predominately 12 metres. Leave them for the first part of another dive… tomorrow.
  6. Make your ascents slow and deliberate. Don’t lose control of your buoyancy – the ascent is the most important part of the dive to your body.
  7. When ascending always take the time to ease into your safety stop. If you have a 5m stop planned for 5 minutes, why not stay there a bit longer if air permits? Your buddy can do the same thing J.
  8. When ascending try to keep your arms and legs at full stretch – Holding a camera? Hold it in one hand and let your arms out so they are not bent at the elbows. For your legs – No bends at the knees. This will ensure good blood flow through your body without any potential restrictions for nitrogen micro bubbles to build up. – (This is a precautionary move- which whilst not proven to be a guaranteed fix, it is yet to be proven otherwise).
  9. If you break the surface before you have completed your safety stop, go back down to the depth you should have been at (5metres) and start your safety stop again.
  10. If you go into DECO then make sure you do all compulsory stops at the depth required and then complete a full set of Safety Stops – 5m for 5 minutes then 3 m for 3 minutes. If in doubt and air permits… stay longer.

After The Dive:

  1. Hydrate – Drink – as soon as you get out of the water, get the equipment off your back and grab a bottle of water (or sports drink) to replenish any salt which your body sweats out – yes it is true… you can still sweat when you dive. Even if you don’t feel like a drink – have one anyway.
  2. Avoid Exertion – Leave the boat anchor to someone who didn’t dive OR if that isn’t possible, wait until you have had half an hour of rest time (not time since you hit the surface) before you start pulling the anchor and moving tanks around the boat.
  3. Avoid HOT showers. Whilst it is always nice to get out of a cold wetsuit into a hot shower, it is also a known contributing factor to DCS. If you shower – make it a warm one instead of a hot one.
  4. Check your dive profile. Make sure no alarms have been activated on your dive computer and make sure your dive was within the plan. If there were any incidents in the dive which altered the dive plan, make the surface interval longer and the subsequent dive shallower and shorter.

When diving in tropical locations:Perth scuba diving Western Australia ammunition jetty

  1. Keep drinking lots of water.
  2. If you get a tummy bug – don’t dive. It dehydrates you and puts you more at risk.
  3. Adhere to safe diving practices. Yes the water is warm and clear, but the risks are still the same.
  4. Reduce the number of dives you do – don’t increase the number of dives you do. – I am the first one to admit – that when I go overseas I try to do 4 + dives every day. This done over a 7+ day period puts you in the very high risk category. “Sledging” your decompression limits like this will inevitably one day end up going the wrong way and if you happen to be in a remote place with no hospitals or decompression chambers around, things may not end up pretty.
  5. Dive within your training and within your limits. Don’t figure just because you are in the tropics and the DMs are easy going that you can hit that 50m dive you always wanted to tell your mates about… Being prepared (and training is preparation), is crucial in doing extreme depth diving.
  6. Don’t Take Risks – dive safely today and you will be able to do it again tomorrow.
  7. Dive on Nitrox wherever you can. The depth is restricted and the percentage of oxygen is better. Your decompression times are extended but take one from me on this one – try diving Nitrox on Air tables when diving overseas. This will allow a huge buffer and allow you to do those 4 dives in the 1 day albeit that the last couple of dives may be a tad shorter than normal. This way, if you accidentally skip a safety stop and have to go back down to restart it, you know you have been doing all the right things up until then and you are sure to have a safe and easy stop. – Ultimately leading to safer and better future dives.

So there you have it. When you dive, you are always at risk. The amount of risk is 100% dependant on you. The risk can be minimized more by using Nitrox when diving at depths up to 30m. Risk can also be minimized by following the few simple points I have outlined here today. If you follow them, don’t do anything silly and always adhere to them, the chances of you becoming a visitor to the chamber will be massively reduced. Remember that DCS is a blood issue. If you are on medication which affects the blood, then be aware of it. Make your doctor aware of it. AND when overseas – let your DM and tour leaders be aware of it too.

The risk of decompression sickness, once you have had it is increased. There is a risk that if you don’t change your ways you may end up with DCS again – even on what would normally be considered as safe diving practices to most. The best way is to never get there in the first place.

If you do a dive where you think afterwards, “ooh that was a bit close” – the chances are – IT WAS.

If you would like any more information about decompression sickness, avoiding the bends, computer use and understanding, Nitrox diving or anything you consider may be beneficial to you, come in for a chat or email us or call.

It’s one of the things we can do to help and it’s what we at Perth Scuba want to be able to offer to you as our valued customers… Because we care.

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