How Smokers Really Ruin Their Diving

While the addictive aspect of smoking is well known, less known are the other physiologic changes that can affect chronic smokers' diving. Subscriber Edmund Doering (Jupiter, FL), a pediatrician and member of the Undersea and Hyperbaric Medical Society, explains. "Heavy smokers have 5 to 7 percent less hemoglobin available to bind to oxygen, nitrogen or other gases used. This altered oxygen saturation in the blood significantly changes the formulae used to program dive computers and decompression tables, because carbon monoxide binds more tightly to hemoglobin than the other gases."

"Secondly, smokers have altered pulmonary function. Parts of the lung get lots of blood supply but little aeration by alveoli, while other parts get lots of air but little blood. This produces markedly inefficient nitrogen off loading. The second part of smokers' lung is chronic bronchitis, producing the "smokers cough," as well as diffuse inflammation of the airways. The inflammation reduces overall lung function, again in a direction favoring reduced nitrogen offloading."

Ern Campbell, who writes the ScubaDoc blog, also warns about the effects of carbon monoxide. "Your carbon monoxide (CO) level varies with the number of cigarettes you have smoked that day, the length of time since your last cigarette, and your level of activity on the day of the reading. Acceptable CO level for diving is 10 parts per million (ppm) by volume; 10 to 20 ppm yields a mild frontal headache, 20 to 30 ppm gives a throbbing headache associated with nausea, 30 to 50 ppm causes severe headache, fainting and weakness, and 50 to 80 ppm results in coma, convulsions and death.

"Typical end-of-dive-day readings are as follows: 0 to 10 ppm of CO for a non-smoker, 11 to 20 ppm of CO for a light smoker, and 21 to 100 ppm of CO in a heavy smoker. To work out the approximate percentage of oxygen being replaced by CO in your blood, divide your reading by six; 18 ppm of CO means three percent of oxygen in your blood is being replaced by carbon monoxide. If you are a heavy smoker, up to 15 percent of your oxygen is possibly being replaced by carbon monoxide."

Campbell adds that smokers also have nasal and sinus drainage problems. "This markedly increases their chances of middle ear and sinus blocks and squeezes."