Pulse oximeters overestimated oxygen saturation in darker-skinned patients with Covid, causing treatment delays. It was a bit of a national and professional embarrassment when after many decades of ubiquitous use of pulse oximetry, calibrated on patients with light skin, someone finally thought to validate it with arterial blood gases in darker-skinned patients in clinical settings — and found pulse oximetry may dangerously overestimate those patients’ arterial oxygen saturation. Not until 2020 did we learn that more than one in six patients who self-identify as Black