At the height of the Covid-19 pandemic, when many hospitals ran out of beds and ventilators, the fingertip pulse oximeter — a $20 neighborhood drugstore purchase — became a primary arbiter of whether a patient was “sick enough” to gain admission to an emergency room.
This spring, surrounded by antique telescope models in a classroom tucked inside the MIT Museum, 10 students bent over a square-shaped seminar table. They were building basic pulse oximeters from low-cost do-it-yourself (DIY) kits of assorted wirelings from TinyCircuits.
This was just one meeting from MIT class 21A.311 (The Social Lives of Medical Objects), a course taught by Amy Moran-Thomas, associate professor of anthropology and the 2022 winner of the Edgerton Faculty Achievement Award.
Moran-Thomas observed that anthropology’s key frameworks for studying material culture were often missing from spaces of device design and pre-med coursework. She developed the class in 2019 to encourage students to learn from ethnographic approaches, the MIT Program in Science, Technology and Society, and history to explore social inquiries related to health objects.
Zeroing in on a case study concerning a different health material, device, or technology, each session probes what Moran-Thomas refers to as “the social assumptions that get built into objects meant to improve health.”
For the week’s focus on “Politics of Measurement,” students rolled up their sleeves for the lab portion of class, joined by Jose Gomez-Marquez of MakerHealth. He guided the teams through assembling their own oximeter.
Then the students were encouraged to interact with it alongside two prepackaged models that displayed readings from sealed-off “black boxes.” The open-design TinyCircuits models demystified these inner workings, which Moran-Thomas pointed out is a reminder of all the choices that any black box can contain. Students attached the DIY sensors to a microcontroller board, and played with lines of code as they wondered how small edits might impact the readings of sensors held to their fingertips.
Nicole Seman '23, a recent graduate in mechanical engineering, has Type 1 diabetes and uses an insulin pump. She enrolled in the course because being dependent on a medical device is something she knows all too well. In a paper, she wrote about the experience of switching pumps, drawing on an ethnography about what assumptions of “normal” bodies get encoded in global cochlear implants and their sensory futures.
After tinkering with the DIY oximeter, Seman noted how some students immediately reported wide discrepancies when wearing two prepackaged devices at once. “It’s a diverse class, and so we were able to see firsthand how the pulse ox works differently depending on skin tone.”
A class with timely implications
This observation, perhaps obvious in 2023, received tremendous pushback when Moran-Thomas first published a widely read essay in the Boston Review laying out the evidence for how pulse oximeters can offer biased results for people with darker skin.
In the essay, she explained that oximeters gauge oxygen levels in part by measuring color absorption: blood’s iron-containing hemoglobin is brighter crimson-colored when fully saturated with oxygen, and a cooler purple-red when holding less oxygen. To measure this, a pulse oximeter shines two light wavelengths through the skin — but many device developers had not carefully accounted for the ways light is absorbed differently across various skin tones, often designing and testing it with largely white test groups. Distorted measurements can be amplified by algorithms, and Moran-Thomas warned that consequences of this inherent bias could produce device errors with life-altering implications, such as whether a patient is admitted to the hospital or offered oxygen.
In Moran-Thomas’s classroom, students had the opportunity to open up devices and see for themselves the human choices that “black boxes” can encode. It was an elegantly simple example of how easy it is to assume that numbers are neutral in health care — when, in fact, codes and the way they are interpreted are often rife with subtle bias.
She says, “Something I hoped the students would see from this exercise is that many things that are taken to be raw data are actually processed signals, mediated by design decisions and unequal histories. Social assumptions get materialized in how we build technology and make measures.” Those assumptions about who a device’s end users will be directly impacts whether the design and its function are equitable — or dangerously unequal.
The session ended that day with a visit from Tufts University associate professor of electrical and computer engineering and MIT alumna and recent MLK Visiting Professor Valencia Joyner Koomson ’98, MNG ’99. Working in a professional landscape where only 2 percent of engineers are Black women, Koomson presented her work to build a “smart” pulse oximeter that works for everyone, with an eye toward global accessibility.
Moran-Thomas says that Koomson’s presentation showed why equitable design is important, and conveyed to students how such work means much more than just diverse testing: it also takes diversity in engineering and among experts.
Device tours
