MEDizzy - A 55 year old man has smoked 30 cigarettes per day since he

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Respiratory medicine

A 55 year old man has smoked 30 cigarettes per day since he was 15 years old. He is a taxi driver. He finds he is increasingly breathless on exertion. Oxygen saturations are 98% on room air. Examination reveals tracheal tug, reduced cricosternal distance and a barrel chest. He has reduced cardiac dullness and symmetrically reduced air entry. CXR reveals hyperinflation and spirometry reveals moderate airways obstruction. The patient walks 300 m on an incremental walk test before becoming breathless; oxygen saturations are maintained. What pathological change best explains why he is breathless on exertion?

Explanation. In COPD, loss of elastin fibres results in small airway collapse and air trapping during expiration. This dynamic hyperinflation is initially noticed on exertion because expiration time is shortened during exercise. Exercise-induced bronchospasm would be more likely in asthma. There are no examination findings that suggest sufficient pulmonary hypertension to cause breathlessness. There is no reason for the diaphragm to move paradoxically in this case. Central chemoreceptors are stimulated by a rise in CO2, which might be expected in more advanced disease.