COPD and Mucous plugs
Most of the risks of smoking and diving are related to long term usage--the chronic obstructive pulmonary disease that smoking produces over many years. This obstruction is in the terminal airways and the emphysema that's caused can (and does) produce air-filled dilations that can markedly increase your chances of pulmonary barotrauma and arterial gas embolism. Smoking also causes an increase in bronchial mucous production with a concomitant paralysis of the cilia. Mucous plugs then become dangerous to the diver, setting the stage for air-filled sacs that lead to rupture upon ascent.
One other potential problem is the reduction in a smoker's O2 saturation and increase in CO2 retention. At depth, this could become a problem with the increased partial pressures of changing ATAs. I'm not aware of any studies relating to CO (carbon monoxide) retention but it certainly is a consideration in not smoking just before diving.
Effects of Diving On Carbon Monoxide
The effects of partial pressure on CO concentration in inhaled cigarette smoke would be the same as if the CO had come from some other source, such as the atmosphere or from oil lubricated compressors. Carbon monoxide (CO) is a poisonous gas that is odorless, colorless and tasteless. It is formed from the incomplete combustion of fuels, such as heating oil, wood, gasoline, coal, natural gas, propane or charcoal. When heating units or motors are not working properly, or if their exhaust fumes are not vented outdoors, carbon monoxide can build up inside your building.
Acceptable CO level for diving operations is 10 ppm by volume (.001%); 10-20% COHb yields a mild frontal headache, 20-30% COHb gives a throbbing headache associated with nausea, 30-50% COHb causes severe headache, fainting and weakness while 50-80% results in coma, convulsions and death. CO binds with hemoglobin 220-290 times greater than O2 and shifts the oxyhemoglobin curve to the left.
Your carbon monoxide level varies with the number of cigarettes you have already smoked that day, the length of time since your last cigarette, how the cigarette was smoked and your level of activity on the day of the reading.
Typical end-of-day readings are as follows: 0 - 10 ppm of carbon monoxide-non-smoker 11 - 20 ppm of carbon monoxide-light smoker 21 - 100 ppm of carbon monoxide-heavy smoker To work out the approximate percentage of oxygen being replaced by carbon monoxide in your blood, divide your reading by 6.
For example: 18 ppm of carbon monoxide divided by 6 = 3% of oxygen in your blood is being replaced by carbon monoxide If you are a heavy smoker, up to 15% of your oxygen is possibly being replaced by carbon monoxide.
Most smokers also have nasal and sinus drainage problems. This markedly increases their chances of middle ear and sinus blocks and squeezes.
There have been studies that have shown that stopping smoking prior to surgery actually increased the amount of mucous production for about a week. Taking this information to diving ---one would have to say that if you are going to gain any benefit from stopping--then you need to have stopped at least one week in advance. If you can do this-- then why not just stop forever?
The effects of diving on nicotine should not be any different with the patch than the effects of diving after smoking. The difference is the continued effect of the patch, whereas the smoker dives after a nicotine load and has a load of carbon monoxide to contend with.
A problem might arise with a change in the the release and absorption of the drug from saturation with saltwater. This is only a supposition as the effect of bathing has been taken into account by the drug company.
Pressure would have no effect as the drug is not in gaseous form. Another possibility is that the saltwater might increase the chance of dermal reaction to the patch -- a side effect that already is fairly high with it's use.
Finally, one must consider the possible physiological changes of the combined effects of nicotine and cold water immersion or just simple immersion. To my knowledge, there have been no studies on this subject.
Smoking Cessation Abstracts