![]() ![]() Many hospitals that purchased these devices for the first time didn't even realize the newer oximeters were missing features that had previously existed in other models, because the "pulse ox" was their first exposure to noninvasive oxygen measurement at all. So when American companies began commercializing the Japanese bioengineer Takuo Aoyagi’s “pulse” addition to oximetry models, they adopted his insights without giving equity considerations a public-facing accounting the way their predecessors had for US markets. ![]() You could tell the story of these lost oximeter features as a case of happenstance: When Hewlett-Packard shifted its focus away from medical devices in the '80s, most of the smaller firms that came to fill the hospital device niche didn't have the kind of broadly applied, multidisciplinary experience that years of working with NASA had brought. But like any history, it is useful to ask who wrote it and what’s left out. The history of devices often gets written later as if this had always been the case-that alternative approaches didn't succeed because they were inferior. We tend to assume that technology will unfold with a kind of linear progress, and that useful features or key questions will be built into future models. Without care, a coming generation of optical color sensors could easily reproduce the unequal errors for which pulse oximetry is now known across many other areas of medicine. Some, like certain optical sensors for sepsis or blood glucose, may already be at your local hospital or present in your home. Having these conversations now is crucial: As part of AI’s growing role in health care, a wide range of noninvasive sensors are being developed with the pulse oximeter as their model. While ear oximeters still exist in specialty niches, by far the most common models in ERs and homes today are nonadjustable and built to fit the “average” geometry of a man’s finger, at times producing suboptimal readings for all others that may well compound with other errors. This choice helped prevent building ableism into oxygen measures, while also avoiding gender disparities due to poor device fit. Instead, Hewlett-Packard placed its sensor on the top curve of the ear, one of the last parts of the body to be impacted by circulation issues during illness. ![]() The sensor was not made for the fingertip, for instance, because then the device wouldn’t work as well for patients with common health conditions such as shock, sepsis, and certain chronic illnesses. Unlike modern pulse oxes that are tested only on healthy people, Hewlett-Packard’s device was designed to work for people who may be sick. The oximeter could also account for circulation idiosyncrasies. Subscribe to WIRED and stay smart with more of your favorite Ideas writers. There are now widespread calls for redesigning the “pulse ox”-as well as rethinking the review systems that failed to catch or prevent these errors for decades. The issue has since been taken up by senators and the FDA, drawing intense interest from doctors and engineers, as well as confused patients. “When a pulse oximeter says 91 percent, more than 50 percent of Black patients actually had a value less than 88 percent,” notes study coauthor Tom Valley. It wasn’t until a team of physicians at the University of Michigan reinvestigated the device last December that the broader medical community began to pay more attention. Some patients of color who told ER doctors they couldn’t breathe well were actually sent home when the device indicated they didn’t need oxygen. But when Covid-19 first hit, pulse oximeter readings were nonetheless hailed as a “biomarker” for early hospitalization and during triage. Since these devices assess oxygen in the blood through optical color-sensing, they can be riddled with errors for people with darker skin, due to racial biases in the calibration process. It’s a technological dinosaur, but in certain ways, its inner workings are more advanced than many devices that measure blood oxygen in hospitals today.įor decades, researchers have documented that many pulse oximeters commonly used in hospitals do not meet FDA safety thresholds for people of color. A professor of medicine at Yale, Meir Kryger, reached out afterward with a suggestion: I should also look into the models predating contemporary pulse oximeters, specifically one made by Hewlett-Packard. I bought it on eBay late last year, after writing a story about the racial bias built into oximetry for the Boston Review. A product of the 1970s, its alarm for low blood oxygen levels is set by analog dial. The gray oximeter sitting on my kitchen table looks like a record player.
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