Pulsus paradoxus

Pulsus paradoxus is an inspiratory fall in systolic BP greater than 10mmHg.

In a ‘normal’ person the systolic BP usually falls around 6mmHg in inspiration. The ‘paradox’ refers to the fact that although the radial pulse is absent, heart sounds can be auscultated.

The commonest cause of pulsus paradoxus is cardiac tamponade (sensitivity 98%, specificity 83%) 

Other causes of pulsus paradoxus include: 

• Acute MI 
• Asthma 
• Severe COPD exacerbation 
• Tension pneumothorax 
• Large PE 
• Large pleural effusion 

Pulsus paradoxus can be measured by 

• Cuff sphygmonanometry 
• Arterial waveform analysis 
• Pulse oximetry waveform analysis 

References 

Bandinelli, G., Lagi, A. and Modesti, P. Pulsus paradoxus: an underused tool. Intern Emerg Med. 2007; 2(1): 33-35. 

Khasnis, A. and Lokhandwala, Y. Clinical signs in medicine: pulsus paradoxus. J Postgrad Med. 2002; 48(1): 46-49.