How can I differentiate between emphysema and chronic bronchitis in a patient with COPD?

To differentiate between emphysema and chronic bronchitis in a patient with chronic obstructive pulmonary disease (COPD), focus primarily on clinical features, symptom patterns, and investigations. Chronic bronchitis is characterised by a chronic productive cough with sputum production for at least three months in two consecutive years, often accompanied by frequent winter bronchitis and persistent cough. Patients typically present with a history of chronic cough and sputum, but may have less pronounced breathlessness initially. Emphysema, on the other hand, is characterised by destruction of alveolar walls leading to airspace enlargement, resulting in progressive breathlessness and less sputum production. These patients often have weight loss, reduced exercise tolerance, and a more prominent breathlessness symptom profile without significant sputum production ¹.

On examination, emphysema patients may show signs of hyperinflation such as a barrel chest, reduced breath sounds, and prolonged expiration, whereas chronic bronchitis patients may have more wheezing and signs of airway inflammation. Spirometry confirms airflow obstruction in both but does not differentiate the phenotypes; however, transfer factor for carbon monoxide (TLCO) is often reduced in emphysema due to alveolar destruction but relatively preserved in chronic bronchitis ¹.

Imaging such as chest X-ray or CT scan can help differentiate: emphysema shows hyperinflated lungs with flattened diaphragms and areas of low attenuation on CT, while chronic bronchitis may show increased bronchial wall markings without significant emphysematous changes ¹.

Additionally, sputum culture may be useful in chronic bronchitis if sputum is purulent, reflecting airway infection or colonisation, which is less typical in emphysema ¹.

In summary, emphysema is distinguished by predominant breathlessness, weight loss, reduced TLCO, and radiological evidence of alveolar destruction, whereas chronic bronchitis is characterised by chronic productive cough, frequent infections, preserved TLCO, and bronchial wall thickening on imaging. This integrated approach combining clinical, functional, and radiological features is supported by NICE guidelines and reinforced by clinical literature emphasising the importance of symptom patterns and investigations in differentiating these COPD phenotypes (Martinez, 1998; Flenley, 1988) ¹.