A shark-fin appearance on capnography is most typical of which condition?

• A. Pulmonary Embolism
• B. COPD
• C. Pneumothorax
• D. Asthma

Answer: (B)

Shark-fin capnography signals severe expiratory airflow limitation with uneven, slowed emptying of alveoli. When expiration becomes markedly obstructed, different lung regions empty at different rates, so the expiratory limb of the capnogram is prolonged and the plateau loses its smooth, flat shape. This produces the characteristic fin-like appearance. This pattern is classic for obstructive airway diseases, with COPD being the prototypical example. Asthma can show a similar pattern during a severe attack, but COPD best fits the typical capnogram described. Other conditions like pulmonary embolism or pneumothorax alter the waveform in different ways (often lowering end-tidal CO2 or changing the overall shape), rather than producing this shark-fin expiratory appearance.