CAUSES & PATHOPHYSIOLOGY
Chronic Obstructive Pulmonary Disease
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COPD is a group of diseases that includes both chronic bronchitis and emphysema (Figure 1). COPD "refers to a spectrum of respiratory diseases which are characterized by some mixture of chronic cough, increased sputum production, dyspnea (shortness of breath), airflow limitation and impaired gas exchange."(5) |
Figure 2. Lung characteristics of Chronic Bronchitis.
Figure 3. Lung Characteristic of Emphysema.
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The airflow limitation in COPD is due to chronic bronchitis, emphysema or more commonly a combination of both. |
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Chronic bronchitis is "characterized by a cough that is productive of sputum for at least 3 months per year for at least 2 consecutive years."(5) The chronic bronchitic cough is mainly due to mucus hypersecretion.(1,6) |
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COPD rarely develops in most patients with a chronic productive cough – these patients are generally considered to have ‘simple chronic (non-obstructive) bronchitis’.(1,5) Chronic cough on its own is not diagnostic of COPD. |
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Emphysema is characterized by destruction and enlargement of the alveoli, where gas exchange occurs. Patients do not necessarily experience airflow limitation, and lung function measurements do not correlate well with the degree of destruction.(1,5) |
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COPD is principally characterized by mucus hypersecretion, inflammation, fibrosis, narrowing of the small airways and destruction of alveolar tissue.(6) The airflow obstruction is not fully reversible and progresses slowly over a period of years.(4,7) |
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While the pathophysiology of chronic bronchitis and emphysema can be described separately, most patients have a combination of both (Table 1).
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COPD Risk Factors
