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From the *Department of Anesthesiology, Duke University Medical Center; The Fitzpatrick Institute for Photonics, Duke University; Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina; and The Center for Devices and Radiological Health, United States Food and Drug Administration, Silver Spring, MO.
Address correspondence and reprint requests to Allan Shang, MD, MSE, Box 3094 DUMC, Durham, NC 27710. Address e-mail to shang004{at}mc.duke.edu.
Abstract
BACKGROUND: Pulse oximeter performance in the presence of motion varies among devices and manufacturers because of variations in hardware, software, testing, and calibration. Compounding these differences is a lack of uniform characterization of motion, and the consequential effects of motion upon the wide range of normal and abnormal human physiology. Traditional motion testing attempts to standardize motion into a reproducible form by using a mechanical jig to produce passive motion of a known amplitude and frequency. This type of motion challenge fails to account for the physiologic changes induced by active movement.
METHODS: We postulate that a more appropriate method for testing the performance of pulse oximeters in the presence of motion is to create a feedback control loop between the device and the test subject, providing a reproducible, actively created, and controlled motion test suitable for standardized testing among manufacturers. It is hoped that relying on a signal as seen from the oximeter's perspective will enable the creation of a sensitive and reproducible test method capable of separating those oximeters that can reject motion artifact from those that cannot.
RESULTS: Preliminary results have concentrated on building the tools and clinical protocols needed to evaluate this method. Some basic observations are reported, but insufficient numbers of experienced subjects precludes rigorous conclusions.
CONCLUSION: We have set the stage for a feasibility demonstration using a novel form of testing. With sufficient subjects and proper statistical evaluation, a robust test method for assessing the performance of pulse oximeters in the presence of motion may be at hand.
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