Dr Peter Wilmshurst has been a qualified doctor for over 25 years. He has served on the BSAC Medical Committee since 1977 and also advises the HSE on diving.
How safe are try dives 
What responsibilities do diving club officers have for ensuring that individuals are medically fit to dive in a pool in a come and try session Helen
 Scuba diving, even in a swimming pool, may be hazardous for individuals with certain medical conditions. Diseases that can cause sudden unconsciousness may lead to drowning. Epilepsy and serious heart diseases are examples. People with significant lung disease can be at risk of pulmonary barotrauma, even in a swimming pool, if they use scuba equipment.
Such people must not be allowed to take part in pool try-dives. They will not be permitted to progress to open-water diving, so it would be unfair to whet their appetites with a pool try-dive.
So that anyone with these types of medical conditions is not permitted to participate in a try-dive, all those wishing to take part should fill in a declaration of medical fitness. They should declare that they do not have any of a number of diseases listed on the form.
If they have any of the conditions mentioned on the declaration, medical advice (usually from a medical referee) should be obtained before the individual is allowed to use scuba equipment, even in the pool.
Implant implications
I am due to have breast surgery soon, probably a mastectomy, and would like information about diving with breast implants. I understand that there are several different types and would like to know if they are unsuitable for a diver. Maggie

A In short, I cant imagine how a breast implant can affect the safety of a sport diver, provided the implant is free of gas. But this question raises a number of issues that are not specific to breast implants. I also receive requests for information about other types of medical implants, such as artificial (prosthetic) joints or metal plates and screws inserted by orthopaedic surgeons, lenses by eye surgeons, pacemakers by cardiologists, etc. For each of these, you have to ask a number of questions.
How will the device be affected by increased pressure If it contains gas, it will be compressed due to the increased pressure under water, unless the casing is very strong. If the diver goes too deep for his/her pacemaker, for example, the outer casing may be compressed, resulting in damage to the electronic innards. However, such hydrostatic compression is not a problem with solid or liquid implants such as breast prostheses or orthopaedic plates and screws.
There is a concern that some implants that are biologically inert (but just used for structural support) may be made of materials that are not inert at high pressures. These metals or man-made materials could have biological activity at increased pressure. To be honest, there is very little information on this, but my personal view is that this is unlikely to be a problem for sport divers breathing air or nitrox.
We must also ask whether the device could predispose to adiving-related problem, such as decompression illness. It is hard to imagine how a breast implant could do this.
For orthopaedic implants, the answer is less certain. Divers can develop a condition called avascular necrosis, which affects bones. The cause is debated, but it is related to interference with blood flow to a bone. Clearly, having scews in a bone may have some effect on this process. However, the fact is that there are lots of divers out there with such metal implants in bones and they dont seem to be getting avascular necrosis.
The difficulty we have here is that avascular necrosis takes years to show itself. We may have to watch this space.

Can I have a Grand Day Out
I have a grommet in one ear drum and would like to know when I can dive again. Manama
A Grommets are used to allow air to enter the middle ear of a patient with glue ear. It is not safe to dive with a grommet in place, because water can pass through the hole in the grommet to cause infection in the middle ear.
The grommet will be expelled in due course. After that, diving will be possible provided the drum has healed and the individual is able to equalise pressure in the middle ear via the Eustachian tube.
Malaria warning
Does taking anti-malarial drugs such as Lariam/Mefloquine affect diving Tim
A Increasingly, divers travel to areas of the world where there is a risk of contracting malaria. It is important that divers (and other tourists) take appropriate anti-malarial drugs to reduce the risk of being infected by this potentially fatal condition. Visitors to an area are more at risk of serious infection than the local inhabitants who have some natural immunity.
No malaria prophylaxis is guaranteed to provide 100 per cent protection, but it greatly reduces the chance of being infected. There are four species of malaria parasite carried by mosquitoes. In some parts of the world, members of one species may be resistant to some anti-malarial drugs. So when visiting an area you need to make sure that you take an anti-malarial drug to which the local parasites are not resistant. To find out which is the best anti-malarial drug for the area you are visiting, you need to check with a medical expert.
Lariam/Mefloquine is one anti-malarial. All drugs have side-effects, and this is true for Lariam. A problem for divers is that, occasionally, Lariam has been reported to cause neurological and psychological problems, including convulsions, confusion, behavioural disturbance and dizziness. Clearly, such symptoms under water would be dangerous and after a dive might lead to an incorrect diagnosis of neurological decompression illness.
The difficulty we have is weighing up in each case whether benefit outweighs risk, but usually if you are going to an area where Lariam is the recommended anti-malarial, it is safer to take that than to risk getting infected. In addition, you should try to avoid mosquito bites by use of insect repellents, mosquito nets, etc.

Operational procedure
How long should you refrain from diving after having an appendicectomy Peter
A It is important that after any surgery there has been complete healing of the wound to prevent dirty water getting in. Healing will obviously be delayed if there is wound infection. It is also important to have regained normal full activity so that the diver is able to swim well in the water. This will depend on the seriousness of the operation, the amount of pain remaining and the fitness of the individual.
The operation itself must be one that will not affect fitness to dive, as can be the case after lung or ear surgery. Generally, for an operation such as an appendicectomy, I advise a lay-off from diving for six weeks, provided the surgeon is happy for diving to resume at that time. Gentle and shallow work-up dives are recommended after any lay-off for medical reasons.

Asthma issues
Why is it that asthmatics shouldnt dive How bad does your asthma have to be to limit diving Cathie

A Asthma is a lung condition where the smaller airways narrow when exposed to certain stimuli, such as allergens (eg animal furs, pollens), smoke and dust, emotional stress, cold, exertion and infection. When these airways narrow, it is more difficult for the individual to breathe out. This can cause breathlessness. It can also cause gas trapping, which might cause pulmonary barotrauma in a diver.
The rules on asthmatics diving vary from country to country and between diving organisations. Some impose a total ban on all asthmatics and even on individuals who had asthma as a child, but have now grown out of it. They argue that nobody with a history of asthma can dive safely, no matter how mild it was or how long ago.
In the UK, most take a more liberal view. We believe that individuals with well-controlled and mild asthma can be allowed to dive. We believe that there is less risk of pulmonary barotrauma for such individuals than for smokers. However, before diving is permitted, these individuals must be passed by a medical referee.

We're all ears...
With regard to the Medical Q&A on ear problems in the July issue, the following points need clarification.
As stated, nystagmus is an indication of problems with the ears or balance mechanism. It is a type of jerky eye (not ear) movement.
Ramon asked about transient problems with orientation that occurred on ascent on more than one occasion. Transient orientation problems can occur if one ear clears more quickly than the other as we ascend (or less commonly descend), rather than after surfacing. It is called alternobaric vertigo.
As stated in reply to another question in that section, persistent ear or balance symptoms (such as deafness, tinnitus or unsteadiness) after surfacing could indicate injury to the ear, including round or oval window rupture. Vestibular decompression illness would also be a possibility.