decompression sickness - what's the deal?
The bubble forming in the eye of a snake. That is the first scientific recording of decompression sickness, and it was discovered by a man named Robert Boyle in the year 1670 as he was bringing the animal up from pressure. Boyle did not understand why and how this little bubble was forming, and it was going to take another 200 years before the explanation would be presented.
The first recording of decompression sickness in humans was in 1841 as French coal miners came back up from pressurized mines and showed symptoms such as pain, numbness and tingling in extremities as well as skin rash and coughing spasms. The miners were trying to ease the pain by contorting their bodies in a way that looked like the “Grecian Bend”, a fashion posture of women during that period. From this explanation the condition became known as “the bends.”
Scientist B. Pol and T.J.J Wattelle noticed that the symptoms were occurring as the miners were leaving the pressurized area. Symptoms were then noted to become reduced when pressure was reapplied to the parson in question. This baffled the scientist, why are the symptoms disappearing by an increase in pressure?
In 1870 Physiologist Paul Bert realized that the components of air (oxygen and nitrogen) were affected by pressure as it entered our body. He determined that as they were going deeper thus increasing pressure, more and more nitrogen was being absorbed. On ascent the release of pressure sometimes causes the nitrogen to take form as bubbles. His recommendation was therefore to ascend slowly and if “bent”, to go back down.
Paul Bert described DCS simply, outlining the basics of what Decompression sickness actually is.
In 1906 professor John Haldane started taking interest in these decompression theories. In the first stage of his research he used goats to see how much nitrogen a body could hold before symptoms of DCS occurred. In later experiments he actually used Navy divers, taking them down to extreme depths, for different amounts of time, and surfacing them at different speeds, then recording when symptoms occurred. Using this data, Haldane created the very first dive tables, helping miners and divers to act in a way that prevented them from getting decompression sickness.
Today, research into decompression theory still continues. We can now dive much more safely using the dive tables that have been adapted over the years. We are now able to dive less conservatively, without exceeding the limits, giving us ample time for our underwater adventures! We are now aware what is affected and how we are affected by DCS. So, the question is, how can us recreational divers prevent it?
The Dos and Don’ts
Plan your dive – and dive your plan!
The number one cause of DCS is diver error (that’s right, usually it is our fault!) and usually it is down to your dive profile being in some way faulty. We measurea diving profile using a few different factors, these include: depth, time and ascent rate. By keeping yourself well within the no stop limits, monitoring your ascent rate, not making a “sawtooth” profile, avoiding making reversed profiles and complete a 3 minutes at 5 meters safety stop, you will successfully and significantly decrease the risk of acquiring decompression sickness or DCS. The good thing about these factors is that they are so easily avoided – simply by planning your dive safely, and then diving your plan, without any last minute changes or alterations, you know that you are going to be a safe diver.
However there are many other factors that might contribute to this condition, so diving a perfect profile is not a hundred percent guaranteed to alleviate DCS symptoms unfortunately. Usually everything that’s increasing blood flow through the body increases the amount of nitrogen absorbed, thus causing an amount of risk in contracting DCS.
Hot or cold?
Recent studies have shown that one of the primary factors in getting DCS is your body temperature. Having a warmer body temperature will speed up the process of both the intake and release of nitrogen while colder temperature will slow down this process. Therefore, in a perfect world, the temperature of the water in which you are diving should be colder as you descend and warmer when you begin to ascend and make your safety stop.
Understanding diving you quickly realize that keeping that temperature profile is close to impossible as the water is cooling our bodies 20 times faster than they would be cooled in normal air, no matter what the water temperature is. So the general recommendation is to stay as cool as possible before, during and after diving. By preventing overheating, you’re reducing the amount of nitrogen absorbed in your body – and therefore reducing the risk of DCS.
Don’t swim so fast!
Another factor that contributes to symptoms of decompression sickness is exertion before, during and after diving. Keeping your exercise intensity as low as possible will reduce blood flow and again – reduce the intake of excess nitrogen. During the dive it is mainly the descent and bottom part of the dive that may be a worry, as this is when the absorption is actually happening. Keeping joint forces as low as possible for as long as possible after the dive will minimize the risk of bubbles forming and spreading around the body.
Although this is not considered being one of the main factors, dehydration has an impact on our circulation as the blood doesn’t flow as easily as if we would have been hydrated. The circulatory system helps us release nitrogen faster and more efficient, thus reducing the amount of nitrogen in our bodies as we are reaching the surface.
Let’s go for a run!
Keeping your physical fitness and general health in check will not completely eliminate the risk the DCS, however studies have shown that living a healthy lifestyle will help us cope with harder conditions without getting overexerted. Studies also show that subjects with higher amounts of cholesterol were more susceptible in getting decompression sickness.
Staying safe, knowing your limits and not exceeding them, as well as maintaining a healthy lifestyle is the best way for you to keep safe while diving. And of course, diving with a PADI dive center you can be safe in the knowledge that you will be well looked after and taught to a high standard.