The pulse is known to be a stationary wave of the heart and blood vessels.

Discovered by Dr. Rene Leriche and applied clinically by Nogier, the Vascular Autonomic Signal (VAS) is simply a change in the quality of the pulse in response to various stressors to which the body may be exposed.

The pulse is known to be a stationary wave resulting from the intersection of the waves generated through the pumping action of the heart and similar waves that have already been reflected from points of branching and of tapering of the blood vessels into small resistance vessels (capillaries).

Consequently, the intensity of the pulse will change depending on the status of the vascular resistance of the capillaries. The reflecting wave either reinforces or weakens the incoming wave. Nogier called a reinforced pulse wave a "positive VAS," which is described as being fuller, vibrant, bulging, or harder. He called the weakened pulse wave a "negative VAS" which is described as soft, hollow, or dull.1 The VAS may be defined as a physiologic response of the vascular system brought on by exposure to macro-information as well as micro-information. Such a response is mediated by the autonomic nervous system, causing changes in the amplitude of the peripheral pulses.

The VAS changes are best felt over the radial artery. Obviously, any stressor that the body perceives will stimulate the autonomic nervous system, leading to increased sympathetic tone, which results in vasoconstriction of the peripheral blood vessels, including the capillaries. This will re-enforce the reflecting wave leading to an increase in the amplitude of the stationary pulse wave, which Nogier labeled as "positive VAS."


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