Smoking & Diving

The negative health effects of smoking are largely known. It is generally advised that smoking and diving are two activities best not performed together. Yet, for some, the habit is hard to break. National statistics indicate that 16.4% of South Africans are smokers. The number of scuba divers who smoke is unknown, but for those divers who smoke or who have a dive buddy or instructor who smokes, it is worth being aware of the risks associated with smoking and diving. The relationship between smoking, diving and health can be explored by looking at the health effects of smoking, the health effects of diving and the interaction between smoking, diving and one’s health.

Smoking can damage almost every part of the body. It is associated with lung cancer as well as cancer of the head or neck, lung, stomach, kidney, pancreas, colon, bladder, cervix and bone marrow (leukaemia). Chronic health effects associated with smoking include stroke, blindness, gum infection, aortic rupture, heart disease, lung disease, hardening of the arteries, reduced fertility and an increased risk of hip fractures ­— all of which have an impact on fitness to scuba dive. A smoker’s overall life expectancy is reduced by up to 17.9 years as compared to non-smokers. At any age, mortality in smokers is 40-80% higher than in non‑smokers.

Smoking is strongly associated with medical conditions affecting the cardiovascular system (CVS) and respiratory systems. The link between smoking and lung cancer was evidenced as early as in the 1930s by German scientists. Yet, the effect of smoking on the lungs encompasses more than just an increased risk of developing lung cancer. The immediate effects of smoking on the respiratory system include impaired ciliary function, increased mucus production, persistent coughing, non-specific airway hyper-responsiveness (AHR) and decreased physical performance.

The cilia are tiny hairs which line the respiratory tract. They move in a co-ordinated manner to clear mucus and foreign particles from the lungs. Without adequate ciliary function, the individual relies more on coughing to clear harmful substances and phlegm from the airways.
Irritants, like smoking, may predispose individuals to non-specific AHR. AHR is the tendency for bronchial constriction in response to certain substances. Bronchial constriction is the abnormal tightening of the airways, which makes breathing more difficult. For a scuba diver with AHR, even the compressed air released from the cylinders (which is colder and dryer than normal air) may cause bronchial constriction. The same is true for the accidental aspiration of sea water and for exertion. Numerous studies have shown a high percentage of smokers with AHR and it has been suggested that smokers with AHR are at an equal or greater risk than asthma patients when diving.     
Increased levels of physical activity require that more oxygen be delivered to the muscles. In those who smoke, oxygen uptake is impaired as a result of the effects of smoking on the lungs. This decreases the body’s reserve to cope with more demanding situations, such as those associated with diving. These may include activities such as a strenuous walk to the sea while fully kitted when conducting a shore entry or when swimming against a current while on the water’s surface. The long-term health effects of smoking on the lungs include the development of chronic bronchitis and emphysema which form part of the disease spectrum known as chronic obstructive lung disease (COPD).   
The CVS includes not only the heart, but also all the blood vessels. It works together with the lungs to ensure adequate oxygen delivery to the organs. This is important for scuba divers. Long-term effects of smoking on the CVS include an increased risk of atherosclerosis, thrombosis and high blood pressure. However, even short-term exposure to cigarette smoke results in transient vasoconstriction, namely the narrowing of the blood vessels. This can impair the inert gas washout after a dive.

Two important systems to consider when diving are the respiratory system and CVS. The main function of the respiratory system in diving is the provision of oxygen (O2) to the bloodstream and the elimination of carbon dioxide (CO2). At rest, the average healthy adult has a breathing rate of 12 to 15 breaths per minute with an average exchange of 500 mℓ air per breath or 6-8 ℓ per minute. This results in the delivery of approximately 250 mℓ of O2 and the elimination of 200 mℓ CO2 per minute. At the level of the alveoli, gas exchange occurs. This is mainly the movement of O2 from the lungs into the blood and CO2 from the blood vessels into the lungs. Certain effects are exerted on the lungs when diving. These include:
  • A decrease in chest wall compliance as a result of the water pressure, wetsuit and gear;
  • A decrease in lung compliance and volume as a result of fluid shifts within the body;
  • An increased density of the breathing gas as a result of increased pressure;
  • An increased risk of barotrauma or lung injury as a result of pressure change; and
  • The lungs acting as a bubble trap.
Immersion in water results in a central shift of blood in the body. Other stressors affecting the cardiovascular function include exposure to cold, the increased partial pressure of O2 and the increased work it takes to breathe. All of these effects increase the heart’s work rate.

The optimal functioning of one’s heart and lungs are essential to managing stressful situations in the diving environment. It is also crucial for adequate inert gas removal from one’s body when diving. The damage to the body associated with smoking results in inadequate gas exchange. This, together with the cardiovascular effects, impairs O2 delivery as well as inert gas washout. A study on smoking and decompression illness (DCI) found an association between smoking and an increased severity of DCI. A significantly higher severity of DCI was found when comparing “light smokers”, “heavy smokers” and people who have never smoked before. Divers are also at an increased risk of acute bronchoconstriction as a result of AHR and lung barotrauma. In some cases, these may occur simultaneously.

An important component of fitness to dive is having the physical reserve to cope with the various additional demands that are placed on the body in the underwater environment. The ability to adjust to the environment is compromised when the body has been damaged by cigarette smoke. Consequently, a diver with a smoking history may not be able to meet the same physical demands in stressful situations in comparison to a diver who does not smoke. It has previously been noted that divers who smoke risk more severe injuries.

The good news is that many of the adverse effects associated with smoking are reversible after cessation. The extent of recovery is influenced by the smoking history prior to cessation as well as the length of time after cessation. Nevertheless, it is always worth quitting as, compared to continued smoking, the risks of adverse health outcomes decrease (and in certain cases the complete reversal of smoking-related damage may even be possible) over time. This serves as an encouragement to those who are currently smoking and are thinking about quitting or to ex-smokers wondering if it was worth kicking the habit. It definitely is worth it! The additional margin of safety that smoking cessation affords divers may well be compared to the conservative use of dive tables and should be encouraged for the very same reasons.

In summary, smoking and diving are strongly discouraged. There is indeed some irony in watching a smoking diver patiently waiting to fill his or her ultra‑clean compressed air cylinder while exhaling a plume of carbon monoxide (CO). Still, encouragement is generally better than ridicule or criticism. Those who do not smoke, but have a buddy or instructor who does, should also be aware of the risks and advise them against it in an informed and constructive manner. Most smokers are fairly hardened against the social outcry and isolation their habit imposes on them. Many smokers experience significant guilt and shame, although few admit to it, therefore accusation is unlikely to be productive. The focal areas of any campaign against smoking should be the health preservation of divers and to reduce risks. Testing a diver who smokes’ true motivation for stopping his or her habit is often conducive to honest conversation. And, for those who actually admit a true desire to quit, there are medication like bupropion (Zyban) and varenicline (Champix) that may offer significant relief. Obviously, medical interventions are not without cost or potential side-effects; in fact, it is strongly recommended that divers discontinue diving during the four to eight weeks that they are on medication. Still, the R400 to R600 for medication and the short-term sacrifice of not diving justifies the many long-term gains in health benefits and the financial savings of kicking the habit. If safer diving is your ultimate goal then smoking cessation should also be.
  • Buch et al. Cigarette Smoking and Decompression Illness Severity: A Retrospective Study in Recreational Divers. Aviation Space and Environmental Medicine; 2003; 74(12): p1 271-1 274.
  • Dillard, T.A. & Ewald, F.W. Jr. Invited Commentary: Should divers smoke and vice versa. Aviation Space and Environmental Medicine; 2003; 74(12): p1 275-1 276.
  • Meintjes, W.A.J. Powerpoint Presentation. Respiratory Fitness for Diving. 2013.

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