A Persistent Problem Hidden in Plain Sight   For decades, pulse oximetry has served as a cornerstone of clinical monitoring—offering a quick, noninvasive estimate of blood oxygen saturation (SpO₂). Yet, the COVID-19 pandemic exposed a long-standing and underappreciated flaw: pulse oximeters can overestimate oxygen levels in individuals with darker skin pigmentation .  Inaccurate SpO₂ readings may mask hypoxemia , delay treatment decisions, and contribute to existing health di