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.
I have heard that people with sickle cell disease or sickle cell trait can have problems when diving. Could you give me some information about the problems that might occur when diving with these complaints I am of Afro-Caribbean descent and have sickle cell trait. Do I need to take any special precautions when diving

Oxygen is carried in red blood cells in combination with haemoglobin. Its the combination of oxygen with haemoglobin which converts blood from blue (lacking bound oxygen) to red.
     There are in fact a number of slight variations on the haemoglobin in our red cells. One is haemoglobin S. The S stands for sickle, because red blood cells containing haemoglobin S are often sickle or C-shaped rather than round.
     We inherit haemoglobin varieties from both our mother and father, and it is possible to inherit haemoglobin S from one or both parents. This can result in half of a persons haemoglobin being haemoglobin S (which we call sickle trait) or all of it (which we call sickle disease).
     Haemoglobin S has advantages and disadvantages. An advantage is that it is difficult for malaria parasites to infect red cells containing it, so for generations having haemoglobin S had an evolutionary advantage in places where malaria was common, such as Africa. Sickle disease and sickle trait are conditions affecting people whose ancestors came from Africa.
     The disadvantage is that when the oxygen content of blood is low, red blood cells containing haemoglobin S take up a C-shape.
     These cells tend to jam in blood vessels and block them. In essence, we believe this represents a large problem when there is a double measure of haemoglobin S (ie, those with sickle disease) and we advise those individuals not to dive.
     We dont think this represents a problem for those with only a single measure of haemoglobin S and in this case we would let them dive.
Policy on grommets
A friend of mine is all set to do a diving course later in the year. He mentioned that when he was young he had an operation to put grommets in his ears. At the time he was told he could not do any deep diving. Is a PADI Open Water course to 18m classed as deep

Grommets are usually used to treat children with glue ear. The ear drum seals up when they come out. If a person has grommets in, he should not dive at all, even to very shallow depths. Once the grommets are out, diving is permitted, with no particular depth restriction, provided the diver can clear his ears without difficulty. If there is any doubt, he should be seen by an ENT surgeon with some knowledge of diving medicine.
It depends on the puncture
My grandson, aged 17, suffered a punctured lung while playing rugby. He has recovered and is now playing rugby again. Can he resume diving He is an Advanced Diver.

In this case, the punctured lung was almost certainly caused by the sharp end of a fractured rib lacerating the lung to cause a pneumothorax. If so, there was a good reason for the pneumothorax to occur, and in the UK we usually let such individuals resume diving after assessment by a medical referee, who will perform some special tests.
     This situation is very different from having a spontaneous pneumothorax, which occurs during normal breathing. People who suffer this are at increased risk of recurrence, and if this occurs under water, it is likely to be fatal.
     Anyone who has had a spontaneous pneumothorax more than five years earlier might be permitted to dive in the UK (but not in all countries) after special assessment by a medical referee, but those with a more recent spontaneous pneumothorax should not dive.
When a good belch works wonders
I have an hiatus hernia. I have an occasional burp and not much heartburn. Can I dive

An hiatus hernia is a very common condition in which part of the stomach is pushed up through the diaphragm from the abdomen into the chest.
     It often causes heartburn, because the condition allows acid from the stomach to pass easily into the gullet.
     It can also cause other types of chest pain. It might prevent food passing easily through into the stomach, and can cause it to be regurgitated.
     If very large and distended by gas, including swallowed air, an hiatus hernia can press on other structures in the chest. The usual way of relieving this is by belching.
     Many divers have an hiatus hernia and dive without problems. They need to be aware that occasionally the increased hydrostatic pressure under water when diving can press on the abdomen and result in an increase in acid reflux and heartburn.
     If a diver swallows a lot of gas and his hiatus hernia obstructs, the gas in the herniated stomach might expand on ascent to press on the lungs and cause breathlessness. However, gas expansion causing breathlessness in divers is more common in those who have had a surgical repair of an hiatus hernia.
     In these cases the repair can be so good that divers are unable to belch up swallowed gas, and the stomach expands on the ascent.
     If this happens, there are rare instances of the distended stomach damaging surrounding structures.
The verdict on Graves disease
Can you please tell me whether I can continue diving with Graves disease I have had two thyroid operations and would like to know whether the pressure under water will make my eyes worse. I have to put drops in them every hour to keep them moist. If I could dive, what depth would be safest

Graves disease affects the thyroid gland and the eyes. We need to consider each aspect separately.
     In the early stage, Graves disease usually makes the thyroid gland overactive, but in the longer term it damages the gland and eventually causes it to be underactive.
     Whether the thyroid is under- or overactive, its activity can usually be controlled by medical treatment or surgery. Once the thyroids activity is well-controlled, diving can be permitted.
     Graves disease also affects the tissues behind the eyeball, particularly the muscles which move the eyes. These tissues swell, the eyeball is pushed forward and eye movement can be reduced.
     We would be slightly concerned that such individuals will be at greater risk of mask squeeze, but I doubt if that would be so. Provided the patients ophthalmologist had no objection, and vision was not seriously impaired, I would let someone with Graves disease dive.
Getting clear after fits
I have been epileptic for two years and had to stop diving. How many years does one have to go without a fit to be able to dive again

In the UK we allow individuals who have been free of fits and without needing anti-convulsant (anti-epilepsy) drugs for a couple of years to dive again, but we dont let anyone still taking anti-convulsant drugs dive. We are concerned that these drugs may increase susceptibility to nitrogen narcosis