Echo State Network-Based Estimation of Photoplethysmography Sensor-To-Skin Contact Force |
| M. Szumilas, M. Wielemborek
Faculty of Mechatronics, Institute of Metrology and Biomedical Engineering, Warsaw University of Technology, św. A. Boboli 8, 02-525 Warsaw, Poland |
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| A photoplethysmographic signal, widely used in cardiovascular monitoring, is susceptible to the sensor's mounting conditions, including the contact force at the sensor-to-skin interface. We aimed to extract this concomitant parameter from a reflective photoplethysmographic signal to enable better observation of varying measurement conditions. Evaluation of a regressor based on an echo state network yields promising results when modeling the relationship between a reference force signal delivered from a force-sensitive resistor and the infrared and red photoplethysmographic signal components with an average normalized root mean square error of 0.101 (range of 0.051-0.150) for the considered test cases. The echo state network regressors using as few as 10 neurons show potential for deployment and online adaptation in resource-constrained hardware, e.g., microcontrollers. |
DOI:10.12693/APhysPolA.146.369 topics: echo state networks (ESN), photoplethysmography (PPG), sensor-to-skin contact force |