Multi-sensor Cardio-Pulmonary Stethoscope for quantitative lung water measurement

This paper describes the development of a multi-sensor Cardio-Pulmonary Stethoscope (CPS) for measuring not only changes but assesses fluid status in lungs. CPS is a microwave device for noninvasive and continuous monitoring of vital signs and changes in lung water content (LWC). It contains a “chest patch” sensor that measures scattering parameters of 915MHz signal. Measurement results are wirelessly transmitted to a mobile device for remote patient monitoring. Excellent results were obtained in clinical trials at Queen's Medical Center with correlation factors of r ≥ 0.95 for respiration and heart rates. Results from human clinical testing showed correlation factor of r ≥ 0.93 with amount the of fluid extracted from hemodialysis patients. To examine the feasibility of using the multi-sensor CPS system, RF simulations on 3D human thorax were conducted. Obtained results demonstrated the effectiveness of such multi-sensor arrangement in assessing fluid content in lungs. An 8×8 RF multiplexing circuit was developed to experimentally validate simulation results and for use in clinical trials. Three-dimensional simulations and experimental validation results are presented.