Should You Trust Apple’s New Blood Oxygen Sensor?
An Anonymous Coward writes:
Should You Trust Apple's New Blood Oxygen Sensor?:
In the early days of the coronavirus pandemic, it wasn't just face masks and hand sanitizer that flew off drugstore shelves. Pulse oximeters were also in short supply, as news came out that a drop in blood oxygen could be a sign that a case of the coronavirus has taken a bad turn.
These inexpensive and noninvasive electronic devices use LED lights and photodiodes to determine the way red blood cells are absorbing light-oxygenated cells absorb more infrared light than red light, cells that aren't carrying oxygen the opposite. With that information, algorithms can calculate a level of blood oxygenation; for most healthy people that's in the high 90 percentile, in cases of COVID, the numbers dropped into the 80s. So it seemed like a good idea to have one on hand, if you could find one.
[...] accuracy remains a question with many of the pulse oximeters on the consumer market. Says Steve Xu, a physician-engineer who is medical director for the Center for Bio-Integrated Electronics at Northwestern University, "It is relatively straightforward to make a pulse oximeter, even for an undergrad engineering design project, but it is really really hard to make a good one that is clinically dependable."
Is Apple's a good one? It's hard to say just yet. Besides the issues of adjusting to different skin colors, coping with motion, and other design challenges faced by all pulse oximeters, putting the sensors on top of the wrist raises the difficulty level. The devices used in hospitals as well as the standalone gadgets sold in drugstores typically clip onto a fingertip or, sometimes, an earlobe.
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