From the Guidelines
Pulsus paradoxus is defined as a drop in systolic blood pressure >10 mmHg during inspiration, and it is easily detected by feeling the pulse or measuring it with sphygmomanometry, as described in the European Heart Journal guidelines 1. To determine pulsus paradoxus, the blood pressure cuff is inflated above the patient’s systolic pressure, and during deflation, the first Korotkoff sound is intermittent, correlating with the patient’s respiratory cycle.
- The first Korotkoff sound is heard only during expiration when the cuff is deflated to a certain point.
- As the cuff pressure drops further, another point is reached when the first blood pressure sound is audible throughout the respiratory cycle.
- The difference between these two points is the measure of pulsus paradoxus, with a difference greater than 10 mmHg being abnormal, as noted in the guidelines 1. Key points to consider when evaluating pulsus paradoxus include:
- Clinically significant pulsus paradoxus is apparent when the patient is breathing normally.
- When present only in deep inspiration, it should be interpreted with caution. Pulsus paradoxus is most commonly associated with cardiac tamponade, but it can also be found in severe asthma, COPD exacerbations, and constrictive pericarditis, highlighting the importance of accurate measurement and interpretation of this physical finding, as described in the guidelines 1.
From the Research
Definition of Pulsus Paradoxus
- Pulsus paradoxus is defined as a decline in the systemic systolic blood pressure by more than 10 mmHg during inspiration 2, 3, 4, 5.
- It is an exaggeration of the normal inspiratory decrease in systolic blood pressure 5.
Clinical Situations Associated with Pulsus Paradoxus
- Inflow obstruction into the heart, such as exsudative pericarditis or cardiac tamponade 2, 4, 6.
- Extreme respiratory variations in intrathoracal pressure, such as during an asthma attack 2, 3.
- Constrictive pericarditis 4, 5.
- Severe acute asthma or exacerbations of chronic obstructive pulmonary disease 3.
Mechanisms Underlying Pulsus Paradoxus
- Inspiratory increases in right heart filling and output are necessary for pulsus paradoxus to occur 4.
- Inspiration causes increases in right ventricular dimensions and pulmonic and tricuspid velocities, and decreases in left ventricular dimensions and aortic and mitral velocities and left ventricular diastolic compliance 4.
- Doppler studies of pulmonary venous inflow confirm that an inspiratory fall in left atrial filling is necessary for pulsus paradoxus 4.
Clinical Significance of Pulsus Paradoxus
- Early recognition of pulsus paradoxus in the emergency room can help to diagnose rapidly cardiac tamponade 3.
- Measurement of pulsus paradoxus is also useful to assess the severity of acute asthma as well as its response to therapy 3.
- The significance of pulsus paradoxus must be considered in the clinical context, as it may be absent in cardiac tamponade when certain conditions coexist and may accompany disease states other than cardiac tamponade 4.