From the Guidelines
Pulsus paradoxus is confirmed by measuring a drop in systolic blood pressure of more than 10 mmHg during inspiration compared to expiration, as defined by the European Society of Cardiology 1. To confirm this finding, use a manual blood pressure cuff and stethoscope. The process involves inflating the cuff above the systolic pressure and then slowly deflating while listening for Korotkoff sounds during both inspiration and expiration.
- Note the pressure when you first hear sounds during expiration.
- Continue deflating until you hear sounds throughout the entire respiratory cycle. The difference between these two pressure readings represents the pulsus paradoxus. A difference greater than 10 mmHg is considered abnormal and confirms pulsus paradoxus, as stated in the guidelines on the diagnosis and management of pericardial diseases by the European Society of Cardiology 1. This clinical sign is valuable in emergency situations, particularly in conditions such as cardiac tamponade, severe asthma, COPD exacerbations, and constrictive pericarditis. The mechanism behind pulsus paradoxus involves the negative intrathoracic pressure during inspiration, which increases venous return to the right heart while simultaneously decreasing left ventricular filling, resulting in decreased left ventricular stroke volume and systolic pressure, as implied by the definition of pulsus paradoxus 1. Therefore, accurate measurement using a manual blood pressure cuff and stethoscope is crucial for confirming pulsus paradoxus, and it should be interpreted in the context of the patient's clinical presentation and respiratory cycle, as suggested by the guidelines 1.
From the Research
Methods for Confirming Pulsus Paradoxis
To confirm pulsus paradoxis, several methods can be employed, including:
- Palpation: This involves manually feeling the pulse to detect changes in systolic blood pressure during inspiration 2
- Cuff sphygmomanometry: This method uses a blood pressure cuff to measure the change in systolic blood pressure during inspiration 2
- Arterial wave formation: This involves analyzing the waveform of the arterial pulse to detect changes in systolic blood pressure during inspiration 2
- Doppler echocardiography: This method uses ultrasound to measure the flow of blood through the heart and can help detect changes in blood flow during inspiration that are associated with pulsus paradoxis 3, 4
- Pulse oximetry: This method measures the oxygen saturation of the blood and can detect changes in the pulse waveform during inspiration that are associated with pulsus paradoxis 5
Diagnostic Thresholds
The diagnostic thresholds for pulsus paradoxis vary, but a drop in systolic blood pressure of greater than 10 mmHg during inspiration is generally considered indicative of pulsus paradoxis 3, 2. The use of oximetry paradoxus, which measures the ratio of maximum-to-minimum amplitude of pulse oximetry plethysmographic waveforms, has been shown to be a useful diagnostic tool for cardiac tamponade, with diagnostic thresholds of 1.2,1.5, and 1.7 having been identified 5.
Clinical Context
It is essential to consider the clinical context when interpreting the results of these methods, as pulsus paradoxis can be absent in cardiac tamponade when certain conditions coexist, and may accompany disease states other than cardiac tamponade 3, 4.