Unless otherwise indicated, information in this section is from reference 38.
COPD (previously termed 'Chronic Obstructive Lung Disease' by the US Surgeon General), describes the permanent airflow obstruction that develops in cigarette smokers.(1)
Smoking interferes with the body's methods of filtering inhaled air. Chemicals within the smoke, especially hydrogen cyanide, acrolein, ammonia, nitrogen dioxide and formaldehyde, have a direct deleterious effect on the cilia, part of the natural lung clearance mechanism in humans.(3) The cilia, tiny hair-like structures which line the bronchial tubes, collect and sweep away impurities which have been inhaled. Interference with this system can result in an accumulation of mucus and toxic agents in the lungs, thereby increasing the likelihood of developing lung disease.
COPD comprises three separate but often interconnected disease processes. These are:
ð chronic over-secretion of mucus, resulting in chronic cough and phlegm production. This may be associated with low grade infection in the airways (chronic bronchitis).
ð airway thickening and narrowing resulting in difficulty in breathing.
ð damage to the small airways within the lung, eventually causing destruction of elastic fibres and airway sacs (emphysema). This restricts the lungs' capacity to contract and expand and decreases the amount of lung tissue through which oxygen can enter the body.
All three processes of COPD lead to progressive loss of lung function.
Clinically significant degrees of emphysema occur almost exclusively in cigarette smokers, or in individuals with a genetically determined deficiency in the protein alpha 1-anti-trypsin. This deficiency is thought to affect around one in a thousand in the population, and because of their particular susceptibility to emphysema, they should be specially counselled against smoking.(39) The severity of emphysema among smokers increases with the number of cigarettes smoked per day and the duration of smoking. Almost all smokers of more than twenty cigarettes per day show some degree of emphysema.
The chronic nature of these diseases means that those who develop them may continue to live for many years, with various degrees of discomfort and disability. At their worst, sufferers may be dependent on life support systems.
Approximately 82% of deaths due to COPD in men are attributable to smoking, and 76% of deaths in women.(4) Heavy smokers run as much as 30 times the risk of non-smokers of developing COPD.