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Decompression Sickness

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What is DCS?

Decompression Sickness is a term that you, as a diver, will hear mentioned many times throughout your diving career. It is a term used by professionals to describe the two main pressure related sicknesses that commonly afflict divers in an emergency situation: decompression sickness and lung over-expansion injuries.

DCI Can Turn A Beautiful Dive Like This Into A Serious Medical Emergency

Decompression Sickness

 

Decompression sickness, or DCS as it’s more commonly known, is a condition brought on by rapid reductions of pressure exerted on the body. The “pressure” we are talking about here relates to the weight of the water pressing down on a diver when he is submerged. This weight of water subjects him to higher pressures than he would normally have on the surface. When there is a reduction of pressure (the diver ascends towards the surface), it  allows the nitrogen that has dissolved into the body’s tissues to come out of solution and return to gas. This is a perfectly healthy and safe process for the body if it the pressure is dropped slowly (i.e. The diver comes up from a dive at a slow and safe ascension rate of less than eighteen meters per minute), however, if the pressure is decreased rapidly (the diver bolts for the surface) then the nitrogen will come out of solution too fast for the body to handle and it will form bubbles in the tissues and blood. This is extremely dangerous and can lead to a range of medical complications, ranging from sore to fatal. Here’s a brief list of some of the symptoms of DCS, these can arise anywhere from immediately to forty-eight hours from the dive:

  • Joint Pain (The Bends) – ranging from mild tingles to excruciating pain, usually in the large joints such as the knees, elbows, ankles, shoulders and neck. This is why they call it the bends – it makes the diver hobble and makes his body look bent.
  • Skin Bends – Itchy rash, feeling of crawling insects, swelling and mottling of the skin. Usually affects the upper torso and neck area.
  • Brain – confusion, amnesia, dizziness, black outs, headache, vision problems, fatigue or strange behaviour.
  • Spine/Nervous System – Strange sensations, paralysis, chest pain, incontinence, numbness and muscle weakness/twitching.
  • Inner Ear (“The Staggers”) – Hearing loss, extreme vertigo and loss of balance.
  • Lungs (“The Chokes”) – Deep burning chest pain, shortness of breath, pain when breathing and a dry cough.

The Rash of “Skin Bends”… Belly Button Piercing Not Included!

Safe to say that any of these symptoms would ruin your day!

Lung Over-Expansion Injury

 

A lung over-expansion injury is a much more simple condition to explain than DCS though its effects are no less serious. In essence you can think of the human lungs as balloons in the sense that they are flexible containers that expand and contract as air is pumped in and out. Just like a balloon, lungs have a maximum size that they can stretch to without breaking. What happens in a lung over-expansion injury is the diver’s lungs are, for some reason, unable to release air as the diver ascends to the surface which causes the air to expand and over-stretch the lungs. The usual cause for air being trapped in the lungs is simply breath-holding upon ascent. This is problematic because the lungs don’t have any nerves so the diver will feel no pain as the lung is being damaged. This damage will usually result in air being forced into a tissue it’s not meant to go such as the blood, the chest cavity or some other organ. This can be dangerous on a number of levels. Here’s a few of the symptoms that can occur (usually the effects of lung over-expansion injuries are seen and felt immediately – a diver may even reach the surface unconscious):

  • Gas Embolism – Unfortunately this is both the most common of symptoms in lung over-expansion injuries, and the most dangerous. A gas embolism is simply when a bubble of gas from the lung is forced into the bloodstream. This can cause many problems, but the biggest problem occurs if the bubble is able to cross over from the ventricle side of the heart to the arterial side as this may lead to bubbles in the brain which can cause stroke and other serious conditions.
  • Pulmonary Barotrauma – This is simply the medical term for a burst lung caused by breath holding on ascent from a dive. This is the initial cause of all the problems on this list, and is a problem in its self because it heavily reduces the effectiveness of the lung.
  • Pneumothorax – This is the condition which arrises when air is forced into the pleural cavity (the space between the lungs and the chest) and presses on the outside of the lung, this can cause the lung to collapse which makes it very dangerous and potentially life threatening.
  • Interstitial Emphysema – This condition is similar to pneumothorax in that air is forced to escape the lung but in this condition it gets trapped in the other tissues in and around the lung. It is both uncomfortable and dangerous, it requires urgent recompression.
  • Subcutaneous Emphysema – If the gas that leaks from the lung is able to make its way to the skin then it will collect there and crate a puffy and crackly sensation under the skin of the neck and shoulders. This is not normally a serious problem though it certainly is uncomfortable and still requires immediate treatment at a hospital.

Lung over-expansion accidents are one of the main causes of serious injuries amongst recreational divers. This is because a submerged unconscious diver is very likely to suffer a lung over-expansion injury if they float to the surface without assistance (or with untrained assistance). This is why it’s important that if you find a diver that is unconscious under the surface then it’s vital that you hold their regulator in their mouth (to stop water from entering their mouth) and tilt their chin upwards to open their airway which lets trapped air escape their lungs.

 

 

Common Causes Of DCI

 

In the famous words of G.I. Joe: “knowing is half the battle!”…well what about the other half? We know what DCI is, we now need to know what causes it in a diving setting. DCI, as I stated before, is caused by rapid reductions in pressure that are the result of uncontrolled ascents. The question then arrises, why does anyone perform a rapid vertical climb when it is so clearly dangerous? There are many causes, I’ve listed a few of them here with tips on how to prevent these incidents from happening:

  • Panic – This is an obvious candidate, but not one we should overlook. It is bashed into any rescue diver’s head that they must turn all fears and panics into productive problem solving rather than let it spiral out of control into unremitting hysteria. This is drilled into their heads so much because if the diver encounters a problem (or a perceived one) then the last thing he ought to do is compound his woes by adding a DCI to his list of problems. The simple fact is that if a diver begins to freak out then he must do his level best to follow his training and ascend at the appropriate rate.
  • Out Of Air Situation – This is a problem that can easily lead to a panicked diver situation and, in turn, lead to a possible DCI case. When a diver is caught out of air, and is not well experienced then it is quite possible they will attempt a buoyant ascent rather than using a buddy’s alternate air source or performing a CESA (controlled emergency swimming ascent). If they are lucky and don’t hold their breath (which they might if they are in a fear-induced trance) they may only suffer from DCS (in varying degrees of severity depending on depth and speed of ascent). The moral of this story is simple: remember your training and, perhaps more importantly, practice manoeuvres like the CESA periodically to keep them fresh for that one-in-a-million chance that you have a blowout and loose your air.
  • Ignorance – I’ve been banging on about “remembering your training” which is great advice for those that were thoroughly taught about basic emergency practices (as you should have been in your Open Water Course), but the issue arrises when you talk to some students that have been trained at less reputable schools – some people simply don’t know what the safe ascent rate is! Others have never tried a CESA and some have’t even practiced alternate air source ascents! For those people I can only recommend you find a better quality school and get them to do a scuba review with you with special attention paid to the basic life saving techniques that we employ as recreation divers. This advice is also applicable to those older divers who have forgotten these skills or divers that simply don’t spend enough time in the sea – keep your skills fresh!
  • Helping Another Diver – This is a peculiar entry on this list but it is applicable in two different manners. First, as I mentioned above, it is possible to further complicate an unresponsive diver’s predicament by not following proper surfacing protocols (to further re-enforce this: Hold regulator in mouth, tilt chin up to surface, control both diver’s buoyancy, ascend slow). Secondly, it is also very easy for a diver (especially a spooked, novice diver) to bolt into a rescue situation charged on adrenaline and begin the ascent with the injured diver but completely forget their basic training (or ignore it) and drag them up too quick. This is made even more likely by the fact that not all new divers dive with a computer, usually rely on a senior member of the dive group to control ascent rate or simply haven’t made many ascents solo. To combat these possible factors you must ensure than all divers in your group have a dive computer, know how to use it and are capable of ascending on their own using the ascent rate indicator on the computer.
  • Faulty Equipment – To finish off this list I thought I’d put the creeps into all my readers, from novice holiday diver to hardened Tec specialist. You might follow all the procedures and have trained well for the usual emergency scenarios but if your BCD begins to inflate itself, you can’t exhaust air, or you drop your weights then what do you do? In some cases like a stuck auto inflator then it is easy to disconnect the hose and orally modulate your buoyancy but if you aren’t aware of what to do then it could lead to a very stressful and uncontrolled ascent. In the case of a BCD that wont vent air then you must remember your fail-safe dump valves that are so simple that they almost can’t stick (they also dump air much faster which will halt a rapid ascent very quickly). Finally, if you drop your weights and cannot retrieve them (if you are above a deep drop-off for instance) then even with a completely empty BCD you will probably begin to ascend (especially if you normally dive with eight kilos or more). There are a number of things you can do in this situation; exhale your breath from your lungs to reduce your buoyancy and to avoid lung over-expansion injuries, flare your legs and arms out to cause drag and, in serious cases, point your fins to the surface and swim downwards to slow your ascent.

 

Other Ways To Avoid DCS

 

Though lung over-expansion injuries are caused solely by rapid ascents and trapped air in the lungs, it is not enough to simply follow good dive practices to avoid DCS being as there are other factors at play which can make a diver more susceptible to this nasty condition:

  • Alcohol/Drugs – It must be said that it’s fairly stupid to go diving when intoxicated in any form, especially when we’ve just finished discussing how important it is to keep your head clear in a stressful situation. On top of this obvious fact, substances like alcohol and other drugs affect your body and brain in a number of different ways. The most important is the way they alter your circulatory system as this is the mechanism that is most instrumental in avoiding DCS. Remember, I’m not just talking about diving ten minutes after having three tequila slammers, this applies to the hangover you suffer the next day – diving with a hangover is a rubbish idea, especially if the sea is choppy!
  • Hydration – The main reason that alcohol and drugs make you so susceptible to getting decompression sickness is that they dehydrate your body which thickens the blood making it less able to cope with the slight over-saturation of nitrogen that must occur as we surface. You can also become dehydrated even if you’ve been saintly for the last two evenings and have stayed at home playing sudoko. This is because simple things like not drinking enough water and getting sunburnt can also affect your blood consistency. Try to stick to water rather than coke or coffee and ensure you take a large drink before the dive because breathing compressed air will dry you out, you’ll just have to deal with needing to pee for the last ten minutes of the dive!
  • Illness – Most people are sensible enough to avoid diving when they are seriously ill, but if the diver has spent a whole lot of money on a dive trip then they might not be willing to let it go to waste, especially if they are beginning to recover. Depending on the illness this can complicate things in all manner of ways: anything with a fever or that causes lethargy will likely also dehydrate you and affect your circulatory system. If your illness causes coughs, blocked nose, wheezing or any other chest/air passage congestion then you may be putting yourself at risk of getting a lung over-expansion injury or other barotrauma like sinus pain or ear problems.
  • Body Fat/Fitness – Your personal health has a number of different parts to play in making you more or less likely to get DCS. The first aspect is your fitness, if you are very fit then your heart and blood will be free-flowing and will deal with micro-bubbles of gas much better than someone in poor fitness. On top of this, a diver with high body fat runs the added risk of getting DCS because fat is a very slow tissue to release nitrogen, this means that if the diver does a long dive he will take additional time to decompress all the nitrogen in his body. If this same diver were to make a fast ascent he is more likely to suffer DCS than his lithe and healthy counterpart.
  • Exercise During and After Diving – As I said above, anything that changes the way your circulatory system operates also changes your likelihood of contracting a pressure related injury. Exercise makes your whole metabolism speed up, but it also changes where your blood is directed and how fast it flows. If you do extreme exercise during or straight after a dive then you run the risk of accelerating the formation and distribution of bubbles throughout the body. Obviously exercise is part of diving, just don’t go hauling in an anchor single-handedly straight after a row of deep dives!
  • Coffee/Caffeine – This is probably just me being picky as this won’t make much of an impact on most divers, but it might mean the difference between treatable DCS and life-threatening DCS in an emergency. The way caffeine works is it stimulates the body’s production of adrenaline which motivates the brain and body to work harder. One of the main things that gets artificially kick-started is the heart which leads us to the same problems as you encounter when exercising straight after or during a dive. I’d avoid the caffeine hit until you’re on your way home, just to give your heart a rest.

 

Treatment For DCI

 

This is a surprisingly short and simple section being as the initial emergency treatment for all cases of suspected DCI is the same. We do three main things when we are dealing with a patient with pressure related injuries;

  1. Get the diver back to the boat of shore immediately. While you are towing the victim back you will call out for the oxygen kit to be prepared because it is vital that the diver begins to breath one hundred percent oxygen as soon as possible for as long as possible. If the diver is not breathing then you will perform CPR on the boat with the O2  mask in place. It will be necessary to call any other divers back to the boat by signalling them so that you can get moving quickly (usually by banging the boat’s metal ladder or using another underwater audible signalling device). If you are within electronic communication distance of land then you will alert the emergency medical services and possibly contact DAN (Diver’s Alert Network) who can guide your actions and support effort.
  2. Once the diver is awake and breathing oxygen then you should put them in the recovery position with their right side down to reduce the likelihood that gas bubbles will cross over from one side of the heart to the other. You should treat for shock at this point.
  3. Get the diver to a hospital that deals with pressure related injuries and has a hyperbarric chamber. This chamber will re-compress the bubbles and then allow the body to “surface” very slowly, while the diver is assisted with medicine.

This Is The Only Safe Place For A Diver With DCI – A Hyperbaric Chamber

Do not try to fix DCS by doing a “re-compression dive”, it simply doesn’t work because of the time necessary to safely decompress – it can take days!

 

Final Thoughts

DCI is a real risk that every diver should be fully aware of when they don their equipment, and if you do not fully understand the implications of what I’ve said here then I implore you to do some research and get to know the realities of DCI. Otherwise, I hope you follow my advice and remember your training because if you ensure you dive smart then you never need to worry about this terrible condition.

Have you had a case of “the bends”? Do you know someone that has? What do you do to make sure you stay safe? Please feel free to put your comments in the section below, and if you have any questions then I’d be happy to answer them.

Happy bubbles (the safe kind)!

By Jamie Campbell

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Comments

  • Hyperbaric Chamber London said:

    For any questions or for free advice regarding decompression sickness please contact us.
    We operate a 24 hour national Diving Accident Helpline, staffed by experienced and highly motivated Supervisors and Diving Doctors from ‘Divers Emergency Service – UK’ (DES-UK), and manning a fully equipped Multiplace Recompression Chamber.

    Thanks
    Richard

  • Anoki Anderrsen said:

    Hi !
    Actually I’m a diver student from one of our local diving schools here .I’ve been learning a lot of great techniques, so far I have never encountered such things but now I’m pretty much educated and aware with this kind of illnesses .

    Thanks for posting !

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