Question

What is the physiology behind this phenomenon?

Answer 1

Change of pulse depending upon respiration is Pulsus paradox.

Pulse volume increases during expiration and decreases during inspiration. Its physiological basis in the form of flowchart:

Inspiration --> Decreased intrathoracic pressure --> Blood pools in veins --> Decreased venous return --> Decreased stroke volume

Expiration --> Increased intrathoracic pressure --> Increased venous return --> Increased stroke volume

Comments

This is just a normal physiology, pulsus paradox is bit different

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No good. Decreased intrathoracic pressure causes an increased venous return, and thus it increases stroke volume.

Answer 2

In pulsus paradoxus, the decrease in systolic arterial pressure that normally accompanies the reduction in arterial pulse amplitude during inspiration is accentuated. In patients with pericardial tamponade, airway obstruction, or superior vena cava obstruction, the decrease in systolic arterial pressure frequently exceeds the normal decrease of 10 mmHg and the peripheral pulse may disappear completely during inspiration.

Answer 3

pulsus paradoxus also known as paradoxical pulse or paradoxic pulse ,is defined as an abnormally decrease ( more than 10mm Hg ) in blood pressure and pulse wave amplitude during inspiration