Mitigating errors in pulse oximeter-derived estimates of oxygenation and perfusion caused by skin pigmentation with a shortwave infrared pulse oximeter - PROJECT SUMMARY While pulse oximetry is a standard of care that guides management of critically ill patients, there is growing evidence that racial bias in pulse oximeter accuracy may overestimate oxygenation in hypoxic patients with pigmented skin and cause harm by impeding escalation of respiratory support. Pulse oximeters noninvasively estimate blood oxygenation (SpO2) and peripheral perfusion (perfusion index, PI) by detecting tissue absorption of red and infrared LEDs. SpO2 is based on calibration via the modulation ratio R, the ratio of pulsatile and non- pulsatile absorption from one LED divided by the ratio from the second LED, regressed against arterial blood oxygenation (SaO2). Oxy- (HbO2) and deoxy-hemoglobin (Hb) have distinct absorption at these wavelengths and because, unlike melanin, they exhibit pulsatile variation, it was assumed that SpO2 estimates based on the pulsatile signal would be pigmentation-independent. Alarmingly this assumption appears to be invalid as recent work has found that oximeters are more likely to provide falsely normoxemic SpO2 in hypoxemic patients if they are darkly pigmented. Differences in melanin-related absorption and scattering, particularly at red wavelengths, are thought to underly pigmentation-related errors in estimates of oxygenation, and likely also impact estimates of perfusion. However, studies demonstrating pigmentation-related device error have not controlled for other confounding physiologic factors that may impact pulse oximetry, and it is therefore not known if health disparities faced disproportionately by people with pigmented skin may independently drive pulse oximeter errors. Overcoming pigmentation-related pulse oximeter bias and decoupling it from other sources of oximeter error is critically important to ensuring that darkly pigmented patients, who already face inequities in the health care system, are not denied life-saving care due to devices that fail to meet the needs of a diverse population. To solve these problems, we propose (i) utilizing novel experimental systems that allow pigmentation to be varied while other physiologic parameters remain constant, and (ii) shift pulse oximeter wavelengths from red (with high melanin absorption and scattering) to short-wave infrared (SWIR, 900-1700 nm) where melanin absorption and scattering is minimized. Successful completion of the proposed studies will ensure that life-saving pulse oximeter technology serves the needs of patients across the full spectrum of pigmentation and no longer fails an already marginalized community.
