Design of a Wireless Pulse Oximeter for use in a Clinical Diagnostic System

Abstract

<p>For patients at risk of respiratory failure, it is important to monitor the blood oxygen saturation of such individuals to ensure proper perfusion of blood in their system. Preferably this information should be received on a continuous basis. Both of these objectives can be reached via the non−invasive method of pulse oximetry. This is currently used in hospital/clinical settings, however uses wires which in effect bound an individual to an area. The purpose is to create a clinical diagnostic system which takes a few physiologically relevant signals and transmits them wirelessly to a base station. This allows an individual in a clinical or research setting not to be bound to a specific area. This project specifically deals with the design of a wireless pulse oximeter for this system. The oxygen carrying molecule of blood is hemoglobin, which can be either oxygenated or reduced. By using the principle of differential light absorption and the assumption that the transmission of light through the arterial bed is influenced only by the relative concentrations of oxygenated and reduced hemoglobin and their absorption coefficients at the two wavelengths, light intensity will decrease logarithmically according to Beer−Lambert’s law. Using light emitting diodes and photodetectors at two separate wavelengths (one at Infrared, another at red) and electronic circuitry (current-to- voltage converter, filters and amplifiers) we are able to obtain a pulsatile signal which we can post process to obtain an oxygen saturation reading. The theory behind our device, hardware design and the experimental results of the system are presented.</p>