What a contentious topic this one will always be! Here's my 5 cents worth from research I have done for physiology lectures I present:
Studies on acute carbon monoxide poisoning demonstrate that immediately after carbon monoxide is administered, blood flow to the brain increases by up to 400% of its control value. The ramifications of this on CNS oxygen toxicity and acute decompression illness remain in question for further study.
Maximum permissible purity standards for breathing-air allow for a maximum content of carbon monoxide of 10 parts per million. By comparison, a quick drag on a cigarette contains in excess of 500 parts per million carbon monoxide. I am personally curious as to the effect this causes in the diver having a quick drag just before getting in the water to have a dive. Such an increase in cerebral blood flow must surely have an effect on nitrogen perfusion and absorption, and thus influence the risk of neurological acute decompression illness on what may be a normally safe dive - food for thought!!
Also it has been documented that cigarette smoke inhalation after a dive has an affect on pulmonary bubble mechanics that may hinder effective elimination of inert gas and predispose to ADI. As silent bubbles accumulate in the lung filters anyway quite extensively in the initial 30 to 45 minutes after surfacing, it would probably be prudent to avoid that desperate cigarette for a good hour or so after the dive.
Of course just as with almost all other theories in decompression, again these are hypothetical concerns and have not been demonstrated emphatically.
An interesting release, dated 28 April 1998, as reported in the Proceedings of the National Academy of Sciences, states that scientists in Scotland have shown that a smokers fate may depend on a single gene in the body. The gene identified provides a defence against the toxic chemicals in inhaled cigarette smoke. When the gene is disabled in mice, they quickly develop skin tumours in response to cigarette smoke. Professor Roland Wolf, who led the team from Dundee, Glasgow, and Edinburgh, said: It has long been known that our bodies contain factors which determine our sensitivity to cancer-causing chemicals. Now we have shown that a single gene could be profoundly important in protecting us against cancer. The gene is the one responsible for making an enzyme called gluathione S-tranferase that appears to have a protective role, perhaps by helping to break down the toxic chemicals in cigarette smoke, which can otherwise start a tumour developing. The gene is known to be present in humans, and is found in the lungs and bladder, two places where cancer is strongly linked to smoking. It is also known to exist in slightly different forms in different people, with different capacities for detoxifying chemicals. This, the Scottish team believes, may well explain how some people survive to an old age in spite of years of smoking, while others die relatively young from cancer.
....maybe theres some hope after-all.
I'd be happy to email further articles of information I have prepared and currently use as lecture handouts on this and other topics, send me an email and I'll gladly forward by return to anyone who's interested.
kind regards
DENNIS GUICHARD
NAUI Instructor Trainer
IANTD Technical Instructor
HSE Commercial Offshore Diver Medic
IMCA Saturation Life Support Technician
Red Cross Paramedic (level 4) Primary Emergency Care
ASHI First Aid Instructor
Retired Special Forces member
