Pulsus paradoxus is a medical sign characterized by a decrease in systolic blood pressure during inspiration. It is caused by a decrease in venous return to the heart during inspiration, which leads to a decrease in stroke volume and cardiac output.
Pulsus paradoxus is an important sign of cardiac tamponade, a condition in which the heart is compressed by fluid or blood. It can also be seen in other conditions, such as pericarditis, constrictive pericarditis, and severe asthma.