Pulsus paradoxus is an abnormal decrease in systolic blood pressure (more than 10 mmHg) during inspiration, a sign often seen in conditions affecting the heart or lungs, such as cardiac tamponade or severe asthma. 

Here’s a more detailed explanation:

• Definition:Pulsus paradoxus is defined as an exaggerated fall in systolic blood pressure (more than 10 mmHg) during the inspiratory phase of the respiratory cycle.Â
• Normal vs. Abnormal:Normally, there’s a slight decrease in blood pressure during inspiration, but in pulsus paradoxus, this decrease is significantly larger.Â
• Causes:
  • Cardiac Conditions: Cardiac tamponade (fluid buildup around the heart), constrictive pericarditis (inflammation of the pericardium), and severe heart failure can cause pulsus paradoxus.Â
  • Respiratory Conditions: Severe asthma attacks, chronic obstructive pulmonary disease (COPD) exacerbations, and tension pneumothorax can also lead to pulsus paradoxus.Â
  • Other Conditions: Pulmonary embolism, hypovolemia, and certain types of pericardial disease can also cause pulsus paradoxus.Â
• How it’s measured:Clinicians can measure blood pressure during both inspiration and expiration, noting a difference exceeding 10 mmHg as indicative of pulsus paradoxus.Â
• Significance:Pulsus paradoxus can be a valuable clinical tool for diagnosing or ruling out certain conditions, especially cardiac tamponade.Â
• Other names:Pulsus paradoxus is also sometimes referred to as paradoxic pulse or paradoxical pulse.Â