Smoking and scuba diving
- Oxygen is distributed around your body by red blood corpuscles. These are the shape of a Pontefract cake. They are too big to fit down the finest capillaries so fold over to do so. Unfortunately the carbon monoxide in cigarette smoke bonds to a red corpuscle 200 to 300 times more readily than oxygen does. A red corpuscle contaminated with carbon monoxide becomes stiff and won’t fold over to fit down the finest capillaries. This effect is exacerbated by the fact that nicotine is a vaso constrictor, making those capillaries even finer. The lack of oxygen supply can clearly be seen in the blue blotches that appear on a smoker’s skin after a dive. If it is doing this to the skin just imagine what it is doing to the other organs. Remember that the half-life of carbon monoxide in your blood is four to six hours so you should allow anything from 12 to 18 hours between smoking and diving. Just try telling that to your average nicotine junkie!
- Most smokers have a degree of obstructive pulmonary disease caused by their habit, which often manifests itself in the coughing that bronchitis causes. The lungs have a mechanism to keep themselves clean and clear; there are huge quantities of cilia lining the air passages. These are small and hair-like and beat to transport the rubbish up and out of your lungs. Whenever you smoke they stop for around an hour so there is no more cleaning action. In a heavy smoker cilia are absent altogether. This means that all the rubbish stays in your lungs, where it adds to the obstructive pulmonary disease and causes areas of the lung to be cut off and to stop working. As you surface at the end of a dive the air in these areas must escape past obstructions such as mucous plugs; if it can’t then you will have a lung expansion injury. This is why the level of these injuries is so much higher in smokers than non-smokers.
- The increased blood carbon dioxide (CO2) retention and reduced lung function in smokers has been implicated in a higher susceptibility to CNS oxygen toxicity.
- The vasoconstrictor effect of nicotine changes the blood perfusion in the body, making DCS more likely. Loss of lung function reduces nitrogen washout on ascent, also making DCS more likely. What has also been observed in chambers worldwide is that DCS hits on smokers are much worse than DCS hits on non-smokers.
- Smokers are hypoxic because of CO2 retention. This makes deep water blackout far more likely.
- The carbon monoxide in a smoker’s blood has an effect on mental capabilities and skills, impairing judgment. With depth the PP will go up, making this worse. When added to nitrogen narcosis it becomes clear that a diving smoker is likely to have severe judgment problems.
- Up to fifteen percent of a smoker’s blood oxygen is replaced by carbon monoxide. When added to the typical loss of lung function and narrowing of the arteries in a smoker this significantly reduces the ability of the body to take on oxygen, so if called on to do extra work in a stress or emergency situation the body may well be unable to respond.
- Smoking suppresses the immune system. When combined with the circulatory effects already noted this makes ear infections more likely and slower to clear up. People giving up smoking have reported a huge improvement.
- When we dive our bodies undergo a physiological change called a mammalian diving reflex. This is thought to put a greater strain on the heart and may well explain why there are frequent diving heart attacks. Smokers already have a much higher risk of heart attack than non-smokers. The combination of mammalian diving reflex and smoking puts the heart under a very high level of strain.
As you can see, smoking doesn’t sit well with diving. And I haven’t even started talking about the problems caused by platelet aggregation, increased blood viscosity and elevated lactic acid levels — all typical in a smoker — yet.
No wonder that all dive training agencies warn about diving and smoking; GUE goes so far as to specifically prohibit smokers taking their training.
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