Signalprocessing in transmission pulse hemometry

Supplying organs and body tissues with sufficient oxygen is one of the most important vital human functions. Commercial pulse oximeters compute the functional oxygen saturation from relative values (reduced hemoglobin and oxyhemoglobin). Methemoglobin (MetHb) and carboxyhemoglobin (COHb) are not taken into account, since they are considered to be reduced hemoglobin and oxyhemoglobin (RHb, HbO2). The total hemoglobin concentration is not included, and is determined by invasive methods. In this work, a non-invasive pulse oximeter is developed, which finds the entire hemoglobin concentration photometrically, and measures the fractional oxygen saturation and pulse rate. The signal of transmitted light I is processed according to the Lambert-Beer-law. The signal decays exponentially with the thickness d of the irradiated sample and its absorption coefficient alpha (I = I0 e -alpha d), where I0 is the incident light intensity.