Mechanism of Magnetic Pulse Wave Signal for Blood Pressure Measurement

Continuous non-invasive blood pressure (BP) measurement can be realized by using pulse transit time (PTT) based on electrocardiogram (ECG) and pulse wave signal. Modulated magnetic signature of blood (MMSB) is a promising approach to obtain PTT. The origin of MMSB is critical to establish the relationship between MMSB and BP. In this paper, two possible origins of MMSB, blood disturbance mechanism and angular variation mechanism, are analyzed and verified through three control experiments under different conditions. The influence of blood velocity alteration and blood volume alteration on magnetic field is investigated though blood flow simulation system. It is found that MMSB comes mainly from the periodic blood flow while the perturbation caused by angular variation between sensitive axis of the magnetic sensor and geomagnetic field can be neglected. As to blood disturbance mechanism, the change of blood volume plays a decisive role while the effect of blood velocity alteration is negligible.