Pulsus paradoxus

Pulsus paradoxus
Classification and external resources
DiseasesDB	11041
[]

Pulsus paradoxus (PP), also paradoxic pulse or paradoxical pulse, is an abnormally large decrease in systolic blood pressure and pulse wave amplitude during inspiration. The normal fall in pressure is less than 10 mm Hg. When the drop is more than 10 mm Hg, it is referred to as pulsus paradoxus. Pulsus paradoxus is not related to pulse rate or heart rate and it is not a paradoxical rise in systolic pressure. The normal variation of blood pressure during breathing/respiration is a decline in blood pressure during inhalation and an increase during exhalation. Pulsus paradoxus is a sign that is indicative of several conditions, including cardiac tamponade, pericarditis, chronic sleep apnea, croup, and obstructive lung disease (e.g. asthma, COPD).

The paradox in pulsus paradoxus is that, on clinical examination, one can detect beats on cardiac auscultation during inspiration that cannot be palpated at the radial pulse. It results from an accentuated decrease of the blood pressure, which leads to the (radial) pulse not being palpable and may be accompanied by an increase in the jugular venous pressure height (Kussmaul's sign). As is usual with inspiration, the heart rate is slightly increased, due to decreased left ventricular output.

Normally during inspiration, systolic blood pressure decreases ≤10 mmHg., and pulse rate goes up slightly. This is because inspiration makes intra-thoracic pressure more negative relative to atmospheric pressure. The negative pressure in the thorax increases venous return, so more blood flows into the right side of the heart. However, the decrease in intra-thoracic pressure also expands the compliant pulmonary vasculature. This increase in pulmonary blood capacity pools the blood in the lungs, and decreases pulmonary venous return, so flow is reduced to the left side of the heart. Also, the increased systemic venous return to the right side of the heart expands the right heart and directly compromises filling of the left side of the heart. Reduced left-heart filling leads to a reduced stroke volume which manifests as a decrease in systolic blood pressure. The decrease in systolic blood pressure leads to a faster heart rate due to the baroreceptor reflex, which stimulates sympathetic outflow to the heart.

...
Wikipedia