Reflectance pulse oximeter measuring central SaO2 from mouth

A reflectance pulse oximeter sensor (RPS) was developed as a part of a multisensor system that is intended to measure physiological data of human stress or fatigue conditions. The RPS is placed on the maxilla and characterized by easy fitting, firm fixing and better stability against motion. To measure arterial oxygen saturation (SaO2), a reflectance sensor that consists of one photodiode (PD) and light emitting diodes (LEDs) with two wavelengths was designed. In order to improve the fit of the sensor and to increase the pulsatile signal component of the photoplethysmogram, an elastic gum optical shield (GOS) and a reflectance optical shield (ROS) were used on the surface of the reflectance sensor. As a result of a breath holding experiment, the RPS was found to have better correlation with a transmittance pulse oximeter placed on the ear-lobe. Furthermore, it is considered that the SaO2 measured from the maxilla indicates the oxygen supply to the brain. The RPS is able to measure SaO2 from the mouth continuously