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Chronic obstructive pulmonary disease (COPD) is an umbrella term that is used to describe emphysema, chronic bronchitis, bronchiolar disease and chronic asthma. All of these diseases cause obstruction in the lungs and varying degrees of shortness of breath on exertion, cough, sputum production and wheeze.
Emphysema causes irreversible damage to the alveoli, which become expanded, severely reducing the surface area of the lung and thus impeding the normal processes of gas exchange. It is a lack of oxygen passing into the blood that leads to the shortness of breath on exertion experienced by nearly all people with COPD.
Chronic bronchitis is an inflammatory condition of the bronchi,defined by the Medical Research Council as 'a productive cough on most days, for at least 3 months during any 2 consecutive years'. In a person with COPD, the mucus-secreting cells of the bronchi produce more mucus than normal, and the mucus is also far more sticky and difficult to expectorate. Smoking is the primary cause of this overproduction of sticky sputum.
Small-airway damage associated with smoking is an important cause of the airflow obstruction associated with bronchiolar disease. The bronchioles become chronically inflamed and oedematous with hypertrophy of the bronchiolar muscle; the resultant narrowing causes airflow obstruction.
Chronic asthma is asthma that is no longer reversible through the use of a bronchodilator (salbutamol, terbutaline, ipratropium) or does not respond to the removal of a trigger, because over years the bronchioles have become hypertrophied and unresponsive.
Most patients will have two or three of these conditions, and it is more important to know how to treat and manage the presenting symptoms than to distinguish exactly which conditions are present.And while patients often don't understand the term COPD, they do understand emphysema.
The definition of COPD as set out in the NICE guideline on the management of the condition is 'COPD is characterised by airflow obstruction. The airflow obstruction is usually progressive, not fully reversible and does not change markedly over several months.The disease is predominantly caused by smoking. '(1)
COPD in the UK is associated with considerable mortality, and morbidity from the disease places a significant burden on the healthcare system and society as a whole. (2) COPD is now the fifth most common cause of death in the UK, killing more than 27,000 people every year. About 85% of these deaths are caused by smoking. (3) In the UK, nearly 900,000 people have a diagnosis of COPD--about 200 patients in the average practice--and many remain undiagnosed. (1)
WHO IS AT RISK
COPD is primarily caused by smoking, but can be caused by inhalation of noxious gases and irritants, for example, in coal miners,cotton mill workers and people who work with chemicals.There is also a rare genetic deficiency of the enzyme inhibitor alpha-1 antitrypsin that leads to progressive lung damage caused by protease enzymes,which greatly increases a smoker's susceptibility to COPD.
A significant smoking history, ie 20 pack years (Box 1), is important for a diagnosis of COPD. Someone who starts to smoke when they are aged 15 years can easily reach 20 pack years by the time they are 35 years old.
BOX 1. CALCULATION OF A SMOKER'S PACK YEARS (Cigarettes smoked per day/20 [1pack]) x years of smoking = total pack years
If an occupational connection is …