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Some medical conditions cause problems for scuba diving. Here's an introduction to the topic if you're uncertain

Although diving has become an activity that can be enjoyed by almost everyone, there are some medical conditions that are – in doctor-speak – 'contraindicated' to diving. That is to say, diving should not be undertaken with those conditions unless they can be appropriately and safely managed.

A good guide to the various conditions that may cause problems with diving can be found via the World Recreational Scuba Training Council, an association which provides some self-regulatory governance between training agencies.

Not every agency subscribes to the WRSTC, but the general guidelines are widely accepted as the default medical position for all dive training. Prior to undertaking a training program with the likes of PADI and SSI, you are required to disclose your medical history and 'self-certify' as to whether or not you fit the medical requirements for diving. In some countries, all potential divers are required to undertake a brief medical examination by an approved physician. However, in most locations it’s only necessary should you admit to having one of the conditions listed on the medical questionnaire.

Because of the extra cost involved, or potential delay or refusal by a dive centre to commence training, many divers are tempted not to answer the questionnaire honestly. In some cases, the risks of doing so are relatively minor but in others, the potential for serious injury – or even death – becomes a very realistic possibility. You can find the document on the WRSTC website, and if you take a moment to look through it, you will perhaps gain some insight into why this might be the case.

For example – one question is 'Have you ever had, or do you currently have back, arm or leg problems following surgery, injury or fracture?' This is a very broad cover-all question and one might argue that it would be unusual to not have had some problems after breaking one’s leg. However, the practical implications of a childhood fracture, twenty years prior to learning to dive, are probably quite minimal.

On the other hand, if you have had any kind of heart disease or perhaps surgery, the risks of diving without medical clearance multiply dramatically. Previous injuries or surgeries can result in weaker body tissues which may not be immediately obvious on dry land, but they may not be able to endure the increased pressures to which we are subjected underwater. Scar tissue is more prone to nitrogen bubble formation during decompression, increasing the risk of decompression sickness (DCS, also known as ’the bends’)

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Hyperbaric chamber (junrong / Shutterstock.com)

An associated complication with regards to the diving medical is that the field of hyperbaric medicine – the study that covers pressure-related injuries – is a specialist subject, about which your average GP or family doctor may have very little understanding.

One clear demonstration of this happened to me when a student arrived at the dive centre having pre-booked an Open Water course, but as he had asthma, he had very conscientiously downloaded the medical form and visited his GP for clearance to dive. He had asthma which is induced by exercise (as opposed to asthma caused by allergies, which is usually fine), and unfortunately, his GP had written in the notes that the ‘patient has asthma but has excellent lung volume’.

The issue here is that problems associated with diving and asthma do not have anything to do with overall lung volume. They are very specifically to do with the fact that asthma restricts the very narrow passageways in the lungs (the bronchioles), causing air to become trapped inside microscopic air sacs known as the pulmonary alveoli – which is where gas is exchanged between the bloodstream and the lungs.

If this air becomes trapped during an asthma attack then it will rupture the alveolar wall as it expands during ascent, injecting air directly into the bloodstream where it might cause both a collapsed lung and lead to what is known as an arterial gas embolism, a blockage which starves the brain of necessary oxygen leading to what is, in effect, a form of stroke, often with similar consequences.

I sent my student to the local hyperbaric physician, who sent him back restricting him to a maximum depth of 12m.

It is worth noting that asthma (and other conditions) used to be an outright ‘no’ to diving, however medical research over the years has changed the rules so that in many cases, as long as the condition is correctly managed, the likelihood is that the person would be cleared to dive. But it still needs checking

Although it's impossible to go into all the various ailments involved in any kind of detail, it is worth mentioning diabetes as one of the most commonly asked-about medical conditions. Like asthma, diabetics were for a long time barred from diving at all, but research has allowed many diabetics to safely dive, under certain guidelines. Non-insulin dependent (type 2) diabetics who manage their condition through diet alone are usually cleared to dive, however, insulin-dependent (type 1) diabetics are at more risk. Severe hypoglycemia (low blood sugar) can cause a person to lapse into unconsciousness and this is clearly very dangerous should it happen underwater. You can read the Divers Alert Network’s guidelines for diving with diabetes at this link.

There are other illnesses which can be safely managed through medication but it is important to have the correct prescription for diving. This is a classic problem with high blood pressure, a relatively common disease in older people and one which can easily be controlled, but the increased pressure underwater causes some medications to wear off much faster than they do at the surface, which may lead to problems underwater. There are medications which are compatible with diving, but again, it needs to be checked and prescribed by a physician who has some understanding of hyperbaric medicine.

Although diving accidents are rare, a significant percentage are caused by undiagnosed or undisclosed medical conditions. It is therefore with some measure of horror that I read one internet keyboard warrior declare that they 'always lie on the medical because I’ve never had any problems'. It’s a little bit like playing Russian Roulette: just because a participant survived the first few spins of the barrel doesn’t mean the same outcome can always be expected. 

Do not lie on the medical. And be prepared to accept that a dive instructor is well within their rights to refuse training, even if it has been signed by a doctor. Had there not been a hyperbaric physician on hand to check the student I mentioned above, I would have refused him training outright.

If you have any concern at all, please visit a diving doctor prior to commencing training, especially if you are planning to visit a remote location with limited medical facilities. Getting proper clearance to dive will significantly increase the bill (the physician closest to me in the UK charges £100), but if they say ‘yes’, then it may go a long way to relieving the frustration of having to visit a doctor – or being refused training – once you reach your destination.

On the other hand, if they say ‘no’, then it is entirely possible that they have saved your life.

The Divers Alert Network is a foundation comprised of non-profit organisations dedicated to diver safety and medical research. They have regional members in America, Europe, Japan, South Africa and the Asia-Pacific. They have a subsidiary insurance business catering specifically to divers. Their main website is at www.diversalertnetwork.org





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