EEEL Researcher Shao Yang along with collaborators Paul Batchelder and Dena Raley of Clinimark, a Boulder-based company that specializes in accurate pulse oximetry measurements, have developed a new model of pulse oximetry that addresses the disagreement between theoretical calibration curves based on Beer-Lambert’s Law and test results on human subjects. This work was published in the December 2007 issue of the Journal of Clinical Monitoring and Computing.
Pulse oximeters provide a noninvasive measurement of the concentration of hemoglobin with bonded oxygen in arterial blood. Since their introduction, pulse oximeters have become an indispensible means of monitoring a patient’s oxygen levels in operating rooms, emergency rooms, and intensive care units. A pulse oximeter consists of two optical sources, operating at two different wavelengths, and an optical detector. Traditional calibration curves assume a one-dimensional optical path to describe how light is transmitted through tissue. The new model is a two-dimensional model that takes into account the effect of other tissue outside of the blood vessels on the transmitted light. The new model is in good agreement with results from human test subjects, while the old model underestimates the arterial oxygen saturation levels as measured using human test subjects. Currently, pulse oximeters are validated by means of measurements on human test subjects. In these measurements, human test subjects undergo a rigorously monitored process where the arterial oxygen saturation levels are gradually reduced. Because of the dangers related to hypoxia, it is not possible to record oxygen saturation level measurements in human subjects below 60 %.
Contact: Shao Yang, phone 303-497-5409
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