Calibration-Free Pulse Oximetry Based on Two Wavelengths in the Infrared - ISMBE - Biomedical Engineering, International Convention Center Haifa 22.2.2018

Ohad Yossef Hay ^1,3 Meir Cohen ¹ Itamar Nitzan ² Ruben Bromiker ² Yair Kasirer ² Yitzhak Yitzhaky ³ Meir Nitzan ¹ Shlomo Engelberg ¹

¹Department of Physics/Electro-Optics Engineering, Jerusalem College of Technology
²Neonatal Intensive Care Unit, Shaare Zedek Medical Center
³Department of Electro-Optics Engineering, Ben-Gurion University of the Negev

Abstract

Measurement of oxygen saturation in arterial blood by pulse oximetry (SpO₂) is based on the analysis of two photoplethysmographic (PPG) signals at two wavelengths, which have different light absorption spectra for oxygenated and deoxygenated hemoglobin. Commercial pulse oximeters use two wavelengths in the red and infrared regions, which have significantly different scattering and different optical path-length. The use of these wavelengths results in a need for empirical calibration leading to an inherent error of ~4%, which is not suitable for some clinical patients, such as preterm newborns. In this research, we are exploring a pulse oximetry for measurement of SpO₂, based on PPG pulses of two wavelengths in the IR, 760 and 820 nm. Since the difference in the optical path-lengths between the two wavelengths can be neglected, the technique is calibration-free. In measurements on healthy subjects and clinical examinations on pediatric patients, SpO₂ values using two IR wavelengths without calibration were found to be similar to those of commercial devices that are based on calibration.