Pulsus paradoxus refers to an exaggerated fall in a patient’s blood pressure during inspiration by greater than 10 mm Hg. Pulsus paradoxus results from alterations in the mechanical forces imposed on the chambers of the heart and pulmonary vasculature often due to pericardial disease, particularly cardiac tamponade and to a lesser degree constrictive pericarditis. However, it is important to understand that pulsus paradoxus may be seen in non-pericardial cardiac diseases such as right ventricular myocardial infarction and restrictive cardiomyopathy. Additionally, non-cardiac disease states can occasionally lead to pulsus paradoxus including pulmonary disease (severe chronic obstructive pulmonary disease [COPD], asthma, tension pneumothorax, large bilateral pleural effusions, pulmonary embolism), as well as any cause of cardiac compression (iatrogenic during surgery, marked obesity, pectus excavatum). Finally, pulsus paradoxus may also manifest secondary to severe hypovolemic shock.[1][2][3][4]