Dr Ian Sibley-Calder has been a GP since 1988, is a medical referee for the UK Sports Diving Committee and is involved with hyperbaric medicine and commercial diving activities. He is a BSAC Advanced Diver and Club Instructor.

Black-skirted masks - do they make you feel hemmed in when under pressure

I was buying a mask at a well-known London store and remarked that it hardly stocked any masks with black silicone skirts. The sales assistant told me that these were more likely to give a diver the sensation of nitrogen narcosis (because the brain thinks that the diver is deeper than he or she actually is).
I was under the impression that nitrogen narcosis can be caused only by the narcotic effect on your body of nitrogen under pressure (usually at 30m and below). I would hope that they would teach instructors about the dangers of black masks if they exist - please shed some light on this mystery.

Youre right, nitrogen narcosis is a physical effect caused by the increase in partial pressure of nitrogen causing an anaesthetic-like effect on the nerves and brain. The effect is similar to alcohol, and can vary from person to person as well as on a dive-to-dive basis in the same individual.
As when drunk, outside influences can alter the way you feel and the way you perceive things, so it is entirely possible in some people that a black skirt could give a feeling of being closed in, darkness etc, and therefore make the diver feel worse.
I suspect, however, that once a diver is used to a particular mask, the effect would be minimal. As with all aspects of diving, know your equipment and your limits.

Collapsed lung - but look at smokers
Fifteen years ago I had a spontaneous pneumothorax. My doctor and a specialist radiologist say it looks normal now but my doctor has also said he would not recommend that I begin diving. How dangerous would it be
Ive never had any problems swimming or doing other strenuous activities, and Im not aiming to set any depth records - I just want to dive.

A collapsed lung would once have spelt the end of a diving career - but that is no longer necessarily the case.
A history of spontaneous pneumo-thorax used to be an absolute contra-indication to diving. It is still the case that it is a serious condition that needs careful evaluation by an experienced dive doctor, and that getting it wrong is serious, and potentially fatal.
Most incidences of spontaneous pneumothorax occur either in people with pre-existing lung disease or in otherwise fit young people.
There is a high risk (up to 50%) of re-occurrence after the first one but the risk declines after time. Smokers are particularly at risk of pneumo-thorax and of re-occurrence.
The UK Sport Diving Medical Committee has recommended the pragmatic approach of accepting that, in individuals with a history of spontaneous pneumothorax who have had a bilateral pleurectomy (surgery to seal the lungs), or who are unoperated on but have had no pneumothorax for five years, the risk of pulmonary barotrauma is small, and not significantly greater than for many in the general population, such as smokers.
All divers affected should be assessed carefully, looking for under-lying lung conditions, and advised to stop smoking. Also, the risk is greatest at shallow depths, (particularly on ascent) because of Boyles Law.

Should I risk grommets
I have recently taken up diving, which has raised questions over whether I should let my four-year-old son have grommets fitted into his eardrums.
He suffers from glue ear, and will eventually grow out of the problem.
His hearing is affected in winter but tends to improve in summer when his colds disappear. No doctor seems able to tell me whether the scarring caused by inserting grommets will affect him in later life, so that he may be unable to take up diving if he wants to.

This is an interesting question on several levels. Grommets are used when the Eustachian tubes are not functioning properly and there is a negative pressure in the middle ear. The body compensates by producing fluid (glue) to equalise the vacuum.
It is much more common under the age of six, and often resolves itself at that time. In the past, grommet operations were done as a matter of course but now they are done only in severe cases of deafness, where schooling and learning are affected.
The effect of the operation lasts only about six months. Then the grommets drop out, and it often has to be re-done. The complications (beside anaesthetic risk in a young child) are infection (sometimes persistent and difficult to get rid of); chronic perforation (needing surgery to patch the hole); and chronic scarring to the drum (mostly not a long-term problem).
These may cause problems to any future diving career. I have seen all these problems and do not advocate grommet operations unless as a last resort.
It also sounds as if your son only has a winter problem with colds. This will get better as he gets older and his immune system becomes stronger.

Perforated ear-drum
I would like to do a try-dive. However, around 15 years ago I suffered a perforated ear-drum during a dose of flu. I have had no further problems but have been advised to seek medical advice before I can be accepted for the dive.

If your drum has healed and you have had no problems, I see no reason why you should not dive. If you have doubts as to whether you still have a perforation, your GP should be able to help out.
If you have flown and your ears pop to pressure change normally and painlessly, you should be fine.

Back from cancer
My husband, 60 and a non-smoker, underwent a left lower lobe resection for lung cancer last July. His post-op course was complicated by a prolonged air leak and he then underwent a course of two-drug chemotherapy. He finished this several months ago and is back to regular exercise: jogging, playing tennis, golf and working out in the gym. He is feeling great and there is no evidence of cancer on his post-treatment PET-CT scan. We are going on a trip to the South Pacific - can he dive

Congratulations to your husband for making such a good recovery. His diving aspirations may however have to be tempered slightly as a result of both the surgery and chemotherapy.
The trauma to his lungs could leave him vulnerable to barotrauma or, more likely, pneumothorax due to scarring or weakness in the tissue. There may also be an issue with air-trapping.
Some forms of chemotherapy affect the lungs badly, and more details will be needed to assess this risk. As a minimum he will need to see an experienced chest physician interested in diving.
He will require a full lung-function test and probably CT scanning.

Cylinders rigged to be inverted can help if bending the arm is difficult.
Broken elbow
In December 2005 I fell and badly fractured my elbow. I now have limited movement in the joint, though I can get around this by inverting my tanks. When can I get back in the water, and will I be able to carry on gas-diving, or will I have a depth restriction because of the injury

There is a theory that damage to tissues could disrupt the flow of nitrogen out of the body, making DCI more likely. While I remain cautious of injuries affecting the back and spinal cord, I know of no real problems with this sort of injury.
If it has healed, is pain-free and you can adapt - go on diving.

Dont dive sedated
I have been diagnosed with a slight sleep disorder and am taking Clonazepam at night and Modafinil during the day. Is it safe to dive on these medications and, if not, how long should I stop using them for before I dive again

On no account dive on this medication. The sedation effects are great and could affect your safety under water. You will need to have stopped them for a few weeks before thinking of diving, because of the length of time they can stay in the system.

Two barriers to diving
I wish to take up diving but I am deaf in one ear, which causes me balance problems. It comes from meningitis when I was a baby. I have also been diagnosed with extrinsic allergic alveolitis. Is it worth me taking a medical to see if I can dive

The balance problem may or may not be a problem and it would depend on its severity and the way it affects you. A detailed chat with a dive doctor would sort this out.
The extrinsic allergic alveolitis is much more serious, and requires detailed investigation. The term refers to a group of lung diseases resulting from exposure to dusts of animal and vegetable origin.
The problem can take some time to develop but can then cause various problems ranging from acute and sub-acute attacks to long-term chronic problems and damage to the lungs. This would make problems such as air-trapping and barotrauma much more likely.
Detailed lung-function tests to exclude air-trapping and possibly a CT scan may be necessary. You need to see an experienced dive doctor, and may have to accept that this condition could prevent you from diving.