... latter problem is compounded by the fact that persistent airways obstruction in older chronic asthmatics is often difficult or even impossible to differentiate from that in COPD, although a history of heavy cigarette smoking, evidence of emphysema by imaging techniques, decreasing diffusing capacity for carbon monoxide and chronic hypoxaemia favour a diagnosis of COPD (Siafakas, 1995). Chronic bronchitis is defined as the presence of a chronic productive cough on most days for 3 months, in each of two consecutive years, in a patient in whom other causes of chronic cough have been excluded (Medical Research Council, 1965). Emphysema is defined as abnormal, permanent enlargement of the distal airspaces, distal to the terminal bronchioles, accompanied by destruction of their walls and without obvious fibrosis (Snider et al, 1985). Thus chronic bronchitis is defined in clinical terms, whereas emphysema is defined pathologically. A group of synonyms have arisen, which in the UK include chronic ...

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