Frequency Domain SpO2 Estimation Based on Multichannel Photoplethysmographic Measurements at the Sternum

Abstract

Estimating SpO2 from photoplethysmographic measurements at the sternum is a challenging task given sternum’s very low perfusion. Reliable SpO2 estimation requires to specifically tackle the problem of very low SNR by simultaneously increasing the available information and reducing the noise. We propose a novel algorithm that: 1) Intelligently takes advantage of multichannel photoplethysmography to increase the available information; 2) Uses a frequency based approach to exploit the heart beat information from conjointly recorded surface ECG, providing a noise robust SpO2 estimation. Our novel approach has been validated on ten healthy subjects in supine resting condition undergoing a protocol that follows ISO9919 guidelines. The SpO2 values obtained with our algorithm have been compared with the values given by commercial reference devices. Promising results have been obtained for the whole database: an average root mean squared error of 1.7% and 93% of the samples within an absolute error of 3%.