Cardiac stroke volume measurement using a non-invasive wearable electromagnetic resonator

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Alruwaili, Fayez Hamoud
Cluff, Kim

The measurement of cardiac output (CO) parameters is an important tool for the detection of cardio-pathologies and monitoring critically ill patients. There are various existing invasive and non-invasive medical technologies that measure CO parameters at the clinical setting including Transpulmonary thermodilution (TPTD) and echo-ultrasound. The main limitations of the existing medical technologies include the restriction to the clinical setting, intensive training, and accuracy in measurement. In this thesis project, a non-invasive wearable electromagnetic (EM) skin patch resonator was designed, tested, and developed to measure CO parameters, specifically left ventricular stroke volume (LVSV). The wearable sensor is an EM self-resonant patch that configured into a specific pattern to formulate its three passive elements (resistance, capacitance, and inductance). The EM patch has no electrical connection and is powered via an antenna embedded within the patch design. A combination of bench top models and healthy human participants were used in testing the volume sensitivity and ability of the EM skin patch in measuring LVSV. A strong linear correlation (R2 0.99) between the volume changes and changes in the EM skin patch response was observed. Also, the EM skin patch has a detection depth capability up to 11 cm using human like tissue phantoms. Heart rate (HR), LVSV, and CO were measured with the EM patch with an average relative error of 0.209 % (R2 = 0.99), 3.04 % (R2 = 0.96), 3.19 % (R2 = 0.80) and 3.79 % (R2 = 0.88) as compared against impedance cardiography and electrocardiogram. As such, this work presents an EM skin patch that can be a unique solution for measuring CO parameters at point of care settings where access to the sophisticated medical technologies is not found.

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Thesis (M.S.)-- Wichita State University, College of Engineering, Dept. of Biomedical Engineering