Design of a Low-Cost Instrument for Pulse Oximetry

Monitoring the arterial oxygen saturation is very important to detect hypoxemia, as it is the mayor final cause of anaesthetic deaths, and even when the episode is not fatal it can result in irreversible brain damage. This work presents the design of a low-cost instrument for continuously monitoring the arterial oxygen saturation level in the patient?s blood. Two sources of light originate from the probe at two wavelengths (650nm and 940nm). The light is partly absorbed by hemoglobin, by amounts which differ depending on its saturation of oxygen. By calculating the light absorption at the two wavelengths the processor can compute the proportion of oxygenated hemoglobin.