A decrease in SBP >10 mmHg during inspiration. Consistent with cardiac tamponade or acute asthma attack.

 

Patient 1:

This is an older man with effusive-constrictive pericardial disease who developed presyncope and hypotension and was found to have a positive pulsus paradoxus. Note the first Korotkoff sounds at ~ 100 mm Hg, but the sounds are only present during expiration when blood pressure is higher (blood pressure A). The sounds are audible throughout both expiration and inspiration starting around 74 mm Hg (blood pressure B). The difference between blood pressure A and blood pressure B (28 mm Hg) is the pulsus.