Simulation of a Non-Contact Triple-Wavelength Reflectance Pulse Oximeter to Measure Oxygen and Carbon Monoxide Saturations

This paper relates to the design of a novel reflectance pulse oximeter, which can measure not only the arterial oxygen saturation, but also that of carbon monoxide, in a non-contact manner. Such an instrument is especially relevant in the monitoring of patients who have a history of smoking, or those who have been exposed to carbon monoxide poisoning, such as from fires. The remote manner of measurement ensures that the risk of contact contamination is eliminated, and that the instrument can be used on infants as well, especially those born prematurely and having sensitive skin. A novel algorithm was devised which uses light sources of three different wavelengths to calculate the above mentioned saturations. A thorough sensitivity analysis was performed to determine the most suitable wavelengths for the purpose, which were determined to be 660 nm, 640 nm, and 940 nm. A system was designed to leverage the above mentioned algorithm, and the same was simulated using Simulink. The simulation gave satisfactory results, with maximum errors in calculation of oxygen and carbon monoxide saturations being 0.36% and 0.66%, respectively. These results are discussed along with measures that can be used to improve accuracy.