Pulsating negative pressure applied locally, directly on the skin surface increases blood flow, probably due to a combination of dilation of the arterioles and an increased arteriovenous pressure gradient. The pulsating pressure will mechanically increase flow in the veins which have one-way valves. The reason for the pulsations is to avoid setting off the veno-arteriol reflex which constricts arteries when the veins are over-distended. That is also the reason why a constant negative pressure is counter productive.

On the figure below, one can observe in the middle panel, how blood velocities (3) increase during the negative pressure period (1), whereas there is no change in the contra lateral control arm (5) not subjected to pressure pulses.

Live demonstration of increased blood flow velocity in a patient’s artery

The video shows the live Doppler signal measuring blood flow velocity in a small artery in the foot (arteria dorsalis pedis). The recording is done on a patient with reduced peripheral circulation. Six seconds into the recording the negative pressure is applied for 10 second followed by a 7 second period of normal pressure. The sequence is repeated with the negative pressure starting again after 23 seconds and 40 seconds.

Negative pressure pulse (1), blood velocity (2,4) and average blood velocity (3,5) in test arm (3) control arm (5)

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