From the Guidelines
Pulsus paradoxus is defined as a drop in systolic blood pressure >10 mmHg during inspiration, as stated in the European Heart Journal guidelines 1. This condition is characterized by an abnormal decrease in systolic blood pressure during inspiration, which can be easily detected by feeling the pulse or using a manual sphygmomanometer.
Key Characteristics of Pulsus Paradoxus
- A drop in systolic blood pressure >10 mmHg during inspiration
- Diastolic blood pressure remains unchanged
- Clinically significant pulsus paradoxus is apparent when the patient is breathing normally
- The magnitude of pulsus paradoxus is evaluated by sphygmomanometry, where the first Korotkoff sound is heard only during expiration ### Detection and Measurement To detect pulsus paradoxus, measure blood pressure using a manual sphygmomanometer while the patient breathes normally, as described in the guidelines 1. Note the systolic pressure when the first Korotkoff sounds appear during expiration, then slowly deflate the cuff until sounds are heard throughout the respiratory cycle. The difference between these two pressures represents the pulsus paradoxus.
Clinical Significance
Pulsus paradoxus is a significant finding that should prompt immediate evaluation for underlying causes, particularly cardiac tamponade, which may require emergency pericardiocentesis, as it can have a significant impact on morbidity, mortality, and quality of life.
From the Research
Definition of Pulsus Paradoxus
- Pulsus paradoxus is defined as a fall of systolic blood pressure of >10 mmHg during the inspiratory phase of respiration 2, 3, 4, 5
- This condition is characterized by an exaggeration of the normal inspiratory decrease in systolic blood pressure 4
Causes of Pulsus Paradoxus
- Pulsus paradoxus can be observed in cardiac tamponade and in conditions where intrathoracic pressure swings are exaggerated or the right ventricle is distended, such as severe acute asthma or exacerbations of chronic obstructive pulmonary disease 2
- It can also occur in conditions like constrictive pericarditis, asthma, and several other clinical conditions 4
- The reduction in pulse volume during inspiration was first described by Richard Lower in 1669, and later described in bronchial asthma by Floyer in 1850 4
Mechanisms of Pulsus Paradoxus
- Both the inspiratory decrease in left ventricular stroke volume and the passive transmission to the arterial tree of the inspiratory decrease in intrathoracic pressure contribute to the occurrence of pulsus paradoxus 2
- Biventricular interdependence (series and parallel) plays an important role in the inspiratory decrease in left ventricular stroke volume during cardiac tamponade and acute asthma 2
- Inspiratory increases in right heart filling and output are widely accepted as necessary for pulsus paradoxus to occur, and echocardiography has aided considerably in understanding the mechanisms underlying its genesis 5
Clinical Significance of Pulsus Paradoxus
- Early recognition of pulsus paradoxus in the emergency room can help to diagnose rapidly cardiac tamponade 2
- Measurement of pulsus paradoxus is also useful to assess the severity of acute asthma as well as its response to therapy 2
- The sensitivity and specificity of this sign are discussed in the literature, and echocardiography appears to be very accurate and sensitive in evaluating the hemodynamic embarrassment associated with pericardial effusion 6