Apple was in a patent dispute over this feature with Massimo. Their workaround is to calculate blood oxygen on the iPhone, using the sensors from Apple Watch.
The Apple Watch hardware is otherwise the same. The back of the watch shines light of a specific wavelength into your skin and measures the reflected light. Heart rate sensing uses green (525 nm) and infrared (850–940 nm) light; blood oxygen sensing added a red light at 660 nm in 2020.
The iPhone will now calculate the ratio of absorbed red to infrared light, then apply calibration constants from experimental data to estimate blood oxygen saturation.
Interesting that a small change like that is enough to not make it infringe the patent anymore. I guess you have to be really careful when writing patents to cover as much implementation variations as possible.
parsimo2010•5mo ago
Masimo does not have an overarching patent on pulse oximetry, as the overarching technology is several decades old. There are many manufacturers of sensors being used in many applications with various implementations, many of which are not covered by Masimo's patents. Masimo could not write a patent to cover significantly more implementation variations because they would not be granted the patent in that case.
Masimo does have patents on specific implementations of pulse oximetry and sued Apple for implementing specific patented features. This made their legal case pretty solid, but it also made it possible for Apple to continue providing pulse oximetry as long as they avoided the specific IP owned by Masimo.
mikestew•5mo ago
Sounds like my wife’s AW6, which used to have this feature but doesn’t after sending it in for battery replacement (Apple replaces the Watch with a refurb), will continue to not have this feature anymore. IOW, watch that had this feature, doesn’t after battery replacement.
I’m curious why this isn’t settled. Apple has surely floated an offer, and it would appear that Apple isn’t going to budge on this. Were I in charge at Massimo, I’d think some money is better than no money.
delfinom•5mo ago
Apple probably doesn't want to set a precedent that they actually have to pay a little guy for a patent. Patents are meant for big companies to have monopolistic control in this day and age
jjtheblunt•5mo ago
or apple could just buy the patent via buying the company, to your point, i guess.
brandonb•5mo ago
The Apple Watch hardware is otherwise the same. The back of the watch shines light of a specific wavelength into your skin and measures the reflected light. Heart rate sensing uses green (525 nm) and infrared (850–940 nm) light; blood oxygen sensing added a red light at 660 nm in 2020.
The iPhone will now calculate the ratio of absorbed red to infrared light, then apply calibration constants from experimental data to estimate blood oxygen saturation.
More detailed writeup on how the technology works is here: https://www.empirical.health/metrics/oxygen/
echoangle•5mo ago
parsimo2010•5mo ago
Masimo does have patents on specific implementations of pulse oximetry and sued Apple for implementing specific patented features. This made their legal case pretty solid, but it also made it possible for Apple to continue providing pulse oximetry as long as they avoided the specific IP owned by Masimo.