Noninvasive microwave technique for human cardiorespiratory hemodynamic assessments

Abstract

The use of the noninvasive microwave method for measuring changes in lung water content has been previously reported and validated in animal experiments. The approach is based on measuring the transmission coefficient across the thorax and correlating results with changes in lung water content. Presented in this thesis is the extension of this technique to the monitoring of multiple vital signs including heart rate and breathing as well as the changes in lung water content from a single transmission and reflection coefficient measurement with an electromagnetic coupler. Using a short time Fourier Transform based DSP method, it is shown that these vital signs can be accurately detected and extracted from a single microwave transmission and reflection coefficient measurement. Furthermore, new electromagnetic coupler designs were developed to increase the sensitivity for vital sign detection and additional clinical applications. A LABView based GUI was developed and utilized in the experimental measurements on a thorax phantom model, and the obtained data confirmed the validity and accuracy of the proposed approach. The radiation bio-safety aspect of this approach was evaluated using a DASY4 near-field scanner, often used for certifying cell phones. Obtained results for a 30mW input power show that the Specific Absorption Rate (SAR) values are about one third of the FCC RF safety standard at the operating frequency of 915 MHz. The electromagnetic coupler design together with the safety experimental procedure and the extracted vital signs results, were submitted to the Institutional Review Board (IRB) and was approved for human clinical trials.