Apr 10
12
Decompression Illness/Sickness (DCI/DCS)
What is DCI?
The air you breath from your cylinder (as you should remember from your initial dive training!) is about 78% nitrogen. As you dive and the ambient pressure increases, some of that nitrogen is absorbed into your cells (I’m not going into partial pressures here, I’ll save that for another day!). As you release the pressure again, the nitrogen will come back out of your cells, make its way to your lungs by your blood stream and you breathe it out.
However, there are several things you can do that will disrupt this process and instead of staying in solution in your blood, the nitrogen will exit from your cells as tiny bubbles. It is these little bubbles that cause all the problems in your body, which can be fatal.
What Causes the Bubbles?
- Over loading your cells with nitrogen either by not leaving a long enough surface interval between dives, or by doing something that pre-disposes your cells to take on more nitrogen (we cover that further down in the article)
- Surfacing too quickly or not completing sufficient deco-stops or safety stops, in other words you are forcing your body to off-gas much quicker than it should be.
- Flying or decreasing pressure beyond sea level (if you are lake diving in the moutnains – check out the deco rules for that!). Don’t forget that your body has not purged all the nitrogen by the time you surface, depending on how many dives you’ve done and the depth of those dives, you body could need another 3 to 12 hours to release all the nitrogen. It’s best to leave 24 – 48 hours before flying.
How will I know if I get DCI?
There are loads of symptoms you could experience all over your body, but they could include;
fatigue or a heavy body;
joint pains;
confusion or change in personality;
itchy or mottling skin;
vision or hearing problems;
balance problems;
shortness of breath or chest pains;
abdominal pains or nausea.
You could suffer from any or all of these and they could occur from 10 minutes after you get out the water, or not show themselves for 3 days. My advice if you get any of these symptoms is to get it checked out immediately as in some cases DCI can lead to death. I would rather hear I had pulled a muscle than find out too late that I was suffering from DCI.
How can I avoid DCI?
- Don’t do too much exercise before (will make your cells more hungry for oxygen, but they will take on more nitrogen) or after diving (you will increase the rate that your body tries to remove the nitrogen and cause bubbles).
- We all know that smoking is bad for you, but it will also increase the risk of DCI because of the nicotine (causes the blood vessels to constrict thereby slowing the release of nitrogen).
- Don’t allow your body to get dehydrated, be especially aware if you are diving on holiday in a hot country – you will dehydrate much more quickly than you would at home. Don’t drink coffee or alcohol as that will dehydrate you further, and try to stay out the wind and direct sunlight while you are diving.
- We’ve already mentioned the risk of not leaving enough time between dives, make sure you know your timings; check your tables and know how long you need to leave between dives.
- Being cold will also affect your rate of off-gasing. Make sure you are wearing the right equipment for the conditions you are diving in and don’t allow yourself to get too cold. When you are cold, the blood vessels close to your skin will constrict to try to reduce the amount of heat you are loosing. As with the effect of nicotine, the constricted blood vessels will slow the release of nitrogen.
- Nitrogen is 5 times more attracted to fatty tissues than to muscle; so the more fat you have on you, the more likely you are to have a problem with DCI. Obviously every human has fatty tissues in our bodies, but the idea is to not let it get excessive 
. Of course the fitter and healthier you are, the more you will enjoy the physical sport of diving anyway!
- I mentioned the risk of DCI during the female monthly cycle in the article “Diving with a Period“, but to cover it again – there isn’t really enough data to conclude either way whether we are more likely to get DCI at that time of the month than at any other time, so just be careful! As more women get into diving, we learn more and more about the effect of pressure on the female physiology.
What should I do if I get the Symptoms?!
1. If it is available, breathe 100% oxygen and stay hydrated by drinking about 1 litre of non-alcoholic drink per hour.
2. Lie down flat – don’t put the head lower than the body as this may cause the brain to swell.
3. Arrange transport to the nearest emergency department or hyperbaric chamber.
4. Keep all your equipment with you so it can be checked for problems that may have caused your DCI.
In Conclusion…
Learn to recognise what causes DCI and what the symptoms are so you can recognise in yourself, or others when you dive. Think about investing in a dive computer if you haven’t already, they can tell you how long you have at your current dept before you go into a deco-dive, and if you do how long your stops should be. Of course having a computer is no substitute for not checking your tables and planning your dive, but you it will make your dive more flexible and you can change your plan if you have to. A computer will also tell you how long you should stay on the surface between dives – but don’t lend your computer to anyone else during your day of dives!
Now go and enjoy your diving!
