Shark-fin capnography waveforms are most commonly associated with which condition?

• A. Bronchospasm
• B. Pulmonary edema
• C. Pneumothorax
• D. Acute myocardial infarction

Answer: (A)

Shark-fin capnography comes from obstructive airway physiology where expiratory flow is greatly slowed and uneven. When the airways are constricted, gas leaves the lungs in a delayed, irregular fashion, so the expiratory portion of the waveform becomes a sloped, elongated plateau with a blunted, fin-like appearance. This pattern is most typical during bronchospasm, such as in asthma or acute bronchoconstriction, where increased airway resistance distorts the expiratory limb.

Other conditions can alter the capnogram in various ways, but they don’t usually produce this distinctive shark-fin shape. Pneumothorax, pulmonary edema, and acute myocardial infarction may change the amplitude or timing of the waveform or EtCO2, but the characteristic fin on the expiratory phase points to bronchospasm.