Chronic Obstructive Pulmonary Disease (COPD)

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What is Chronic Obstructive Pulmonary Disease?

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Chronic obstructive pulmonary disease (COPD) is a disease of the lung. The lungs are the organs found in the chest which are invloved in breathing. Air enters the nose and mouth, then travels to the lungs via the trachea, which divides into smaller airways called bronchi and, subsequently, bronchioles. (See diagram below). The lung tissue itself is a spongy material, consisting of a series of folded membranes (the alveoli) which are located at the ends of very fine branching air passages (bronchioles). COPD is a disease of the smaller airways in the lungs.

Chronic obstructive pulmonary disease (COPD) is a disease that consists of two pathologies:

Chronic bronchitis: Defined as chronic cough with mucous production on most days for greater than three months, for at least two consecutive years.
Emphysema: Defined as an enlargement of the alveoli and bronchioles, and destruction of the alveolar walls.

These disease processes affect the bronchi and alveolar walls, respectively. The end result of both is the destruction of lung tissue and obstruction of the airways of the lung, leading to impaired gas exchange. The two conditions usually occur together, causing chronic airflow limitation.

Other names for chronic obstructive pulmonary disease (COPD) include chronic obstructive airways disease (COAD), chronic obstructive lung disease (COLD) and chronic airflow limitation (CAL).

Who gets Chronic Obstructive Pulmonary Disease?

Chronic obstructive pulmonary disease (COPD) is a major cause of disability, hospital admissions, and mortality in Australia. It is considered to be ranked third in the overall burden of disease (following heart disease and stroke). More than half a million Australians are estimated to suffer from moderate to severe disease. COPD ranks fourth among the common causes of death in Australian men, and sixth in women. The death rates from COPD in Indigenous Australians are up to five times that of non-Indigenous Australians.

The major cause of COPD is smoking. It is thought that around 10-15% of smokers will develop the disease. Furthermore, as rates of smoking-related diseases are increasing in women, it is thought that rates of COPD will also increase in women, perhaps eventually exceeding rates in men.

Predisposing Factors

Cigarette smoke is by far the most important factor in the development of COPD. If you smoke 30 cigarettes per day, you are 20 times more likely to die from COPD than non-smokers. The more you smoke, the greater your risk of severe disease. Smoking a pack a day for more than 20 years is considered a significant risk in the development of COPD. COPD is therefore largely preventable if you do not smoke.
Familial factors: A family history of COPD may increase your risk of having the disease. This may relate to hyper-reactive airways, a feature of asthma.
Alpha-1-antitrypsin deficiency: This substance is found in several places throughout the body and is important in preventing cells from breaking down, particularly those in the lungs and liver. People who do not have enough of this enzyme are at increased risk of emphysema and cirrhosis of the liver.
Exposure to air pollution.
Recurrent airway infections: This may be important in the development and progression of COPD. Prompt use of antibiotics and vaccinations may help reduce the impact of infections.
Other factors such as urbanization, social class, occupation and diet may also have some impact in the development of COPD, but their overall effect is not known.

Progression

In susceptible smokers, cigarette smoking results in a steady decline in the ability of the lungs to function. Stopping smoking, even late in the course of the disease, may result in mild improvement in lung function and, more importantly, will slow the rate of decline in lung function. Sometimes your lung function can improve back up to the level of a non-smoker.

COPD usually starts when you are in your 50s or 60s. From this point, there is a slow and steady decline in lung function. This can eventually cause disability and impairments, but these are often unrecognised until late in the disease. It is likely that you will require long-term medication treatment. Note that if you are a smoker you may also suffer from lung cancer and cardiovascular disease (such as ischaemic heart diseases) on top of your COPD.

COPD can cause a number of complications:

Secondary polycythaemia: This is an increase in the number of red blood cells in the blood to try to compensate for reduced oxygen levels. The blood subsequently becomes 'thicker' with sluggish flow which can lead to clotting.
Right heart failure
Pneumothorax: This is leakage of air from the lung into the surrounding pleural space due to rupture of a bulla (dilated air space). This can lead to collapse of the lung and may require insertion of a chest drain.
Respiratory failure: This is often caused by acute infective exacerbations. Death can sometimes occur from a severe decline in respiratory function.

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