Pulsus Paradoxus

Pulsus paradoxus occurs when there is a greater than 12-mm Hg decrease in systolic blood pressure during inspiration. 

It accompanies:

• chronic obstructive pulmonary disease,
• pneumothorax, 
• severe asthma,
• pericardial tamponade.

Measurement

The patient should be reclining at a 30° to 45° angle and
instructed to breathe normally.
1. Inflate a standard blood pressure cuff until Korotkoff
sounds over the brachial artery disappear.
2. Lower pressure in the cuff a few millimeters of mercury
per second until the first Korotkoff sounds appear during
expiration.
3. Maintain pressure at this level and observe the
disappearance of sounds during inspiration. Record this
cuff pressure.
4. Very slowly lower cuff pressure until Korotkoff sounds are
heard throughout the respiratory cycle. Record this cuff
pressure.
5. The difference between pressures recorded in the two
previous steps is then recorded as the measurement (in
millimeters of mercury [mm Hg]) of pulsus paradoxus.
A pulsus paradoxus >12 mm Hg is abnormal but
nonspecific (see text).