Towards noninvasive monitoring of total hemoglobin concentration and fractional oxygen saturation based on earlobe pulse oximetry

Abstract

Till now, there is no available device which can measure the total hemoglobin (THb) concentration and the fractional oxygen saturation (SaO2) noninvasively. Finger, earlobe, nose bridge clamp and forehead sensors have been already used to monitor the functional oxygen saturation of the hemoglobin. Earlobe sensor has a lot of advantages that make it attractive for measuring the hemoglobin concentration and the SaO2. The structure of earlobe enables the application of the theoretical discipline with smaller errors. This may enable the calculation of other blood constituents like glucose. Less disturbance of the patient is achieved for monitoring. In cases of low perfusion, the pulse wave velocity will be affected and the time delay problem will be appeared. But the time delay for the earlobe sensor will be stay smaller than the finger sensor. For motion artifact effect in ambulance overcoming, an adaptive filter is used for reliable measurements. The effect of the motion artifact on the earlobe sensor will be also smaller than on the finger sensor. For long time monitoring and for home use the earlobe sensor consumes less power than the finger sensor. Available reformed light emitting diodes (LEDs) with different wavelengths and especially in the infrared region, where the light absorption of tissue is too high, can be applied by the earlobe clip. The noninvasive measurements are based on the Photoplethysmography (PPG) signal which will be studied for the earlobe and the finger sensors under various conditions using Lambert Beer Law (LBL). The difficulties related to the calculations will be also discussed. The study reported that the earlobe sensor can be a suitable sensor under various conditions to calculate the THb concentration and SaO2. © 2009 Springer Berlin Heidelberg.