Supporting more accurate pulse oximetry for every patient

Pulse oximeters provide indirect evaluations of blood oxygen concentration (SpO2) and are widely used throughout the medical professions for diagnosing and monitoring respiratory anomalies in patients. Research shows that commercially available pulse oximeters systematically overestimate true arterial blood oxygen saturation (SaO2) due to the concentration of melanin in the skin. This overestimation in SpO2 puts patients at a greater risk for not meeting the criteria for hospitalization or initiation of ventilator support, which increases risk for mortality or morbidity. No published explanations exist for this well-documented observation and, indeed, the available literature often contrarily states that pulse oximeter measurements are not affected by skin pigmentation. Our theoretical analysis and pilot research, however, demonstrate that the overestimation is due to the use of broadband light-emitting diode (LED) light sources. The broad spectral bandwidths of these LEDs interact with the spectral absorption of melanin concentration in skin to systematically shift the oximeter calibration. This shift causes artificially high values of SpO2 at low blood concentrations of O2, particularly in skin with high melanin concentration. The 3 proposed aims will extend our efforts to date, providing a scientific foundation for eliminating this error and to foster development and promotion of simple, inexpensive, and accurate pulse oximeters. In Aim 1, we will: (a) determine if there are other spectrally-dependent constituents in the finger that change with each pulse; (b) determine how light-source bandwidth interacts with melanin, including whether there are other pulse-dependent changes in spectral transmission through the fingers, and how sensitive SpO2 measurements are to light source bandwidth; (c) specify the practical peak wavelength and spectral bandwidth needed for bias-free pulse oximetry; and (d) fabricate an optimized light source that provides bias-free pulse oximeter measurements for testing in Aim 2. In Aim 2, we will demonstrate that the finger probe developed in Aim 1d provides bias-free pulse oximeter measurements (SpO2) that do not overestimate true arterial oxygen saturation measurements (SaO2) at low blood concentrations of O2. In Aim 3, which will not employ human subjects as in Aims 1 and 2, we will translate our findings (i.e., print, in-person, and social media) to physicians, hospitals, and health care facilities. As part of Aim 3, we will reach out to healthcare professionals to ensure they are aware of the problems with existing commercial pulse oximeters and introduce them to bias-free pulse oximeters once they are available. Finally, we will license the technology to major manufacturers of pulse oximeters to facilitate translation.