HIDDEN LEGACY OF THE BENDS
In terms of serious accidents, diving compares very favourably to sports such as rugby, horse-riding and mountain-climbing. But are we taking this level of safety too much for granted? Diver's Diving Doc, Ian Sibley-Calder, fears that divers are being inadequately informed of the risks of permanent nerve damage
ALL TRAINING ORGANISATIONS MENTION THE BENDS, decompression illness (DCI) or barotraumas to trainee divers. They do so, however, in a sterile, flat, remote way. The facts, figures and descriptions that are given out, often with a pint in the local club/ classroom, seem light-years away from the grim reality of the hyperbaric chamber.
The impression given by most of the training is that DCI is rare (which is correct), but that even if you are unlucky enough to be afflicted, a quick trip to the friendly local hyperbaric chamber fixes you up and you're ready to go back into the sea. There is an expectation of total cure, with minimal fuss.
The introduction of computers and more and expensive equipment has conspired to give the impression that the risk has been reduced. It has led to the expectation that anyone can dive.
This myth is perpetuated by "try-dive" sessions. Often held abroad, and after minimal medical and physical screening, if any, the would-be divers are guided into the water, untrained, often to extreme depths. Once enthused, they are then screened, sometimes to find that they should never have been in the water at all.
It is not unusual for me to be asked whether epileptics, poorly controlled diabetics or people with a history of pneumothorax (burst lung) can dive, and they can be quite upset when I refuse even to consider it. The impression remains that everyone can dive and that we doctors are making a fuss about nothing.
So how safe is diving? Let's look at some statistics:
The Institute of Naval Medicine and the British Hyperbaric Association collects all the statistics of divers who present for treatment to a chamber in the UK. On average each year there are about 220 divers. Of these, 84% are recreational divers, 84% breathing air and diving to an average of 26m. Hardly dramatic dives.
Of these 220 divers, about 150 have DCI, and from Fig 2 you can see that they present in fairly well described ways - ie weakness, sensory loss and general constitutional symptoms.
All this information is well known and taught fairly successfully in the training programs. What is more interesting is Figure 1, the graph that shows treatment outcomes. This indicates that 73.3% of divers who were treated still had symptoms after the initial treatment.
The final outcomes, often after multiple treatments over weeks and months were: full resolution 78.2%, incomplete resolution 21.8%.
This is a long way from the impression that most divers seem to have about miraculous hyperbaric treatment. Divers I have seen, post-treatment, often seem to have residual problems.
Some may be as mild as post-stress disorders but range to symptoms as severe as weakness, incontinence and memory problems. Balance problems such as falling over in the dark, and increased susceptibility to alcohol seem to be particularly prevalent. That's a serious price to pay for an enjoyable sport!
A further interesting statistic involves the 25 divers a year who return to this country after diving abroad with symptoms of DCI - probably as a result of denial of symptoms, or coming back too quickly after treatment in a chamber.
The group of divers with residual symptoms often ask me: "When I am going to get better?"
My answer is that they have had a severe insult to their brain/spinal cord, similar to a stroke. Some improvement occurs as the swelling and bruising resolves, and some occurs as the body "re-routes signals". However, after a year what they are left with will probably not improve significantly. Their condition remains the same often for the rest of their lives.
Divers sometimes feel "let down" by the treatment, feeling that their symptoms should have been resolved. This is not surprising, given the benign way in which DCI is taught and the over-optimistic impression of the results of hyperbaric treatment.
Some of this over-optimism comes, I suspect, from the results of hyperbaric treatment in the commercial sector. Commercial divers have much better results than sports divers, largely because of the speed with which they are treated. They are in a chamber within minutes of presenting, because there is always a chamber on site.
Sport divers often present late to a chamber, either having denied existence of their bend, or diving in places from which transferring them to a chamber takes time. This results in a different mechanism of action of the hyperbaric treatment.
Quick presentation leads to the treatment of the bubble itself, with luck preventing nerve damage in the first place. Late presentation means that in a lot of cases the bubble has already gone, and it is the nerve damage and inflammation around the affected area that is being treated.
My argument is one of risks and the understanding of risks. Everyone knows, and can appreciate, that if you climb a mountain the risk is that you fall off and break something or, at worst, kill yourself. You can train, get all the best equipment but you cannot eliminate all the risk and beat gravity.
Diving risks are like this: you can train, get all the best equipment but at the end of the day you cannot eliminate all risk - you cannot beat the laws of physics or breathe under water. There is no such thing as a risk-free dive.
The difference between the two is transparency - the risk is obvious in climbing, less so in diving. Unless it is taught properly - the negative side to diving as well as the positive - we are not giving divers all the facts with which to make their own risk assessment, and decide whether this is the sport for them.
What about the divers who are already at increased risk, such as those with pre-existing medical complaints. Everybody thinks they can dive nowadays, the risks are low, so why can't they?
The answer is that most people don't assess or act upon the risks of diving.
When trouble does occur, this results in increased risk not only to themselves but also to a buddy or the rescuers. This results in a rise in litigation, which I believe will rise steeply as people start to blame others for what is often their own lack of understanding of the risks.
And what about the young diver, facing that 20% risk of some permanent nerve damage post-DCI? The risks of getting the bend in the first place are small, but would you let your precious child climb high mountains, and should you be taking this risk on their behalf, when they cannot fully appreciate the problems or risks? They might not thank you for any residual nerve damage 10 years down the road.
That divers are at risk is nothing new, but the risks have to be explained and understood. Training can be improved, risks minimised and diving patterns altered, but at the end of the day it is important for them to understand that they are entering a sport that could result in permanent damage to their health or, at worst, death.
from: divernet
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