Pulsus Paradoxus indicated by optical plethysmograph
Pulsus Paradoxus (PP) is an exaggeration of the normal variation in the pulse during the inspiratory phase of respiration in which the pulse becomes weaker as one inhales and stronger as one exhales. It is more technically described as "an inspiratory fall in the systolic blood pressure greater than 10 mm Hg." The "paradox" refers to the fact that heart sounds may be heard over the precordium when the radial pulse is not felt.
Pulsus paradoxus is a pathophysiologic vital sign associated with a variety of life-threatening cardiac and pulmonary conditions such as: colon, cardiac tamponade, severe asthma, COPD, croup, tension-numorthorax, sleep apnea, volvulus of the stomach, severe dehydration or blood loss and pulmonary embolism.