Step 1 First Aid Rapid Practice Test

An exaggerated drop in systolic blood pressure with inspiration, greater than 10 mmHg, is called pulsus paradoxus. The mechanism involves the normal rise in venous return to the right heart during inspiration. In conditions with reduced pericardial compliance or other severe cardiopulmonary stresses (like cardiac tamponade, severe asthma, or COPD), the right ventricle fills more and can shift the interventricular septum toward the left ventricle, limiting left ventricular filling. This pairing of inspiratory effort with restricted LV filling leads to a noticeable fall in systolic pressure during inspiration.

Paradoxical pulse is a term sometimes used in a similar context, but pulsus paradoxus specifically describes the blood pressure change during inspiration. Kussmaul sign refers to a rise in jugular venous pressure on inspiration, not a drop in systolic pressure. Pulsus alternans is a beat-to-beat alternation in pulse strength due to severe left ventricular systolic dysfunction, not the inspiratory BP change described here.