On the Non-invasive Sensing of Arterial Waveform and Hematocrit using Microwaves

Arterial waveforms can provide valuable insights into a patient’s health. Hematocrit (HCT) level, the blood volume concentration of red blood cells, makes up 40 to 50% of the total blood concentration. Dielectric spectroscopy studies focusing on blood have shown that relative permittivity and conductivity vary with HCT levels. This paper presents a novel method to detect the hematocrit levels in the blood and sense the arterial waveform. A finite-difference time-domain (FDTD)-based 2D electromagnetic (EM) simulation with an artery and tissue model was used to detect different HCT levels at 915 MHz. Based on published literature, dielectric parameters for a normal range of HCT levels were assumed from animal blood studies. Additionally, a 2D wrist simulation model was developed at 915 MHz and 2.45 GHz with a multiple-port system. Based on numerical simulations, EM signals were sensitive to different HCT levels and changes in arterial blood volume. The simulation results indicate a great potential for microwave-based non-invasive sensing of HCT levels and arterial waveforms.