Design a non-invasive pulse oximeter device based on PIC microcontroller

This paper presents the design of a non-invasive medical device that is capable of monitoring and measuring the saturation of peripheral oxygen (SpO(2)) in a patient's blood as well as their heartbeat rate simultaneously. Pulse oximetry is based on the different light absorption characteristics of oxygenated hemoglobin (HbO(2)) and deoxygenated hemoglobin (Hb) of visible light to calculate SpO(2). The designed pulse oximeter is based on a microcontroller (PIC 18F4520) and uses a transmitting optical sensor. It consists of three parts: an optical sensor, an analog part, and a digital part. The optical sensor houses two transmitting LEDs and a receiving photodiode. The analog part is used to condition, filter and amplify the oximetry signals (red and IR). The digital part acquires the conditioned oximetry signals for processing and it is also used to save the measured values with time and date of the measurement and display these on an LCD screen. Via an RS232 connection, the digital part sends the measured values and the obtained signals to the MATLAB program that hosted in PC for further processing and more accurate analysis. The designed device was tested and the results showed that the performance was satisfactory and the accuracy of measurements is high.