A novel magnetic plethysmograph for non-invasive evaluation of arterial compliance

Noninvasive evaluation of arterial compliance by measurement of Pulse Wave Velocity (PWV) has proven utility in cardiovascular screening. We present the design of a novel Magnetic PlethysmoGraph (MPG) for non-invasive estimation of PWV. The system uses a Giant Magneto Resistance (GMR) sensor to detect the fluctuations caused by blood flow in an ambient magnetic field encompassing the blood vessel. The design of an Electro Magnet (EM) based MPG transducer is presented. The ability of the proposed transducer to detect the blood pulse waveform is verified by in-vivo tests and an occlusion test. The design is further validated by demonstrating in-vivo measurements of carotid to radial artery PWV. The design of a dual element transducer for evaluation of local PWV is also presented. The proposed dual element plethysmograph is capable of measuring PWV over sections of the arterial tree as small as 15 mm.