Pulsed multifrequency photoplethysmograph

A technical description of a pulsed, multifrequency photoplethysmograph is given. It has four channels, thus featuring two probes, each with two different wavelengths. In this study 950 and 560 nm are used. The penetration depth of light in skin is wavelength dependent, thus making it theoretically possible to record vascular changes in different layers of the skin. Results from skin blood-pressure measurements and rest recordings are presented.