Apple Watch blood oxygen sensor review
According to JBQ, A new validation study published this month tests the blood oxygen feature of the Apple Watch blood oxygen sensor. According to the results of this study, Apple Watch Series 6 is able to reliably detect states of decreased blood oxygen saturation compared to medical grade pulse oximeters. Here’s how to study to determine this…
As spotted by MyHealthyApple, the study was published this month in the open-access journal Digital Health. The purpose of this study was to investigate “how well a commercially available smart watch that measures ambient blood oxygen saturation (SpO2) can detect hypoxemia compared to a medical grade pulse oximeter.”
For this study, researchers recruited 24 healthy participants. Each subject wore an Apple Watch Series 6 on their left wrist and a pulse oximeter sensor (Masimo Radical-7) on their left middle finger. Participants breathed through a breathing circuit with a three-way non-rebreathing valve in three phases. First, during a 2-minute initial stabilization phase, participants inhaled ambient air. Then, during a 5-minute desaturation phase, participants breathed an oxygen-reduced gas mixture (12% O2) that temporarily lowered their blood oxygen saturation.
In the final stabilization phase, participants rebreathed ambient air until SpO2 returned to normal values. SpO2 was measured from smart watch and pulse oximeter simultaneously at 30 second intervals.
The study resulted in 642 pairs of blood oxygen measurements:
JBQ says, Differences in individual measurements between the smart watch and oximeter within 6% of SpO2 can be expected for SpO2 readings of 90% – 100% and up to 8% for SpO2 readings below 90%.
Thus, the researchers conclude:
Bias in SpO2 between smart watch and oximeter was 0.0% for all data points. The bias for SpO2 less than 90% was 1.2%. Differences in individual measurements between the smart watch and the oximeter within 6% of SpO2 can be expected for SpO2 readings of 90% to 100% and up to 8% for SpO2 readings below 90%.
For the first time, Apple has added support for blood oxygen measurement to the Apple Watch Series 6. This feature is also available on the latest Apple Watch Series 7, Apple Watch Series 8 and Apple Watch Ultra. Apple has been hesitant to promote the feature with any real medical claims, and the company hasn’t touted any significant improvements to the technology since it was first introduced in the 2020 Series 6.
The Apple Watch’s SpO2 sensor, which allows users to measure their blood oxygen levels, was a hit when it first came out, but it may be even more accurate than it was initially marketed.
According to a recent study, the Apple Watch oxygen reader is comparable to medical grade pulse oximeters. Although Apple Watches shouldn’t be used in place of official medical devices, it’s good to know that the readings they display are accurate enough to be trusted.
First reported by JBQ, the study was published this month in the journal Digital Health and sought to compare a “commercially available smart watch” with a medical-grade pulse oximeter. The watch used was the Apple Watch Series 6, Apple’s first smart watch with an SpO2 sensor, which is over two years old at this point.
Results apple watch blood oxygen sensor
The results of this study showed that the Apple Watch “can reliably detect states of decreased blood oxygen saturation with SpO2 below 90% compared to a medical grade pulse oximeter.” To reach this conclusion, the study used 24 healthy participants who each wore an Apple Watch Series 6 on their wrist and a Masimo Radical-7 pulse oximeter on the middle finger of the same hand. Participants then performed various breathing exercises to manipulate their blood oxygen levels to see how the Apple Watch performed compared to the Masimo Radical-7. At the end of the tests, there were 642 blood oxygen readings to compare.
To reiterate: if you’re looking to accurately measure blood oxygen levels, it’s still best to use a proper medical device. But the results of this study show that Apple’s wearable technology is certainly moving in the right direction to provide accurate medical information. In addition to the SpO2 sensor, Apple Watches offer alerts for irregular heart rate rhythms that may indicate atrial fibrillation, medication reminders, and sleep tracking.
While Apple doesn’t claim that any of its devices can be used as concrete medical readers, the features that have been added to Apple Watches are particularly useful for those looking to monitor their body’s performance. Having informed conversations with health care providers is very helpful. Should they discover something remarkable?
Blood measurement: finger vs. wrist
To make sense of the Apple Watch’s disappointing readings, I reached out to lung specialists who haven’t had a chance to test the watch but know the science. When doctors test blood oxygen, they often use sensors on the fingers called pulse oximeters. These devices shine light through the skin and nails to detect the color of the blood as a measure of how much oxygen it contains. They produce a measurement called SpO2. Most healthy people range between 95 and 100 percent.
The finger oximeters used by doctors are approved by the Food and Drug Administration. To compare my smartwatch results, I purchased a $ 60 finger oximeter from Medline Industries, which is FDA-approved and reports a plus or minus two percent error rate.
Unlike a finger pulse oximeter, these two smartwatches try to read your blood oxygen from your wrist. And they are conspicuously silent about accuracy. Apple’s new watch has lights on the bottom to generate signals that reflect off the blood on your wrist and are read by sensors. An app lets you do spot checks whenever you want and also runs on its own while you sleep. You have to hold still for a really, really long 15 seconds to read.
The first time I tried this on the Apple Watch 6, it said my oxygen level was 88 percent—shockingly low, considering I’m in good health and not wheezing. Five minutes later I tested again and it said my SpO2 was 95%. I tried it and kept getting different readings – and often, a “measurement failed” error message.
I told Apple about my experience and they sent me a new watch. My first measurement on my second Apple Watch 6 reported my SpO2 as 100%. If these readings were accurate, my lungs were in for a truly brutal Wednesday.
Apple’s new watch ups the ante on its healthcare game
Over several days of comparing Apple Watch II measurements to an FDA approved finger oximeter, Apple’s readings often differed by two or three percent though sometimes they matched exactly, and sometimes they were off by as much as seven percent.
is it just me Skin, fat and blood vessels are different. Apple doesn’t comment on the error rate of its sensor, but spokeswoman Amy Best said, “It’s been rigorously tested on a wide range of users and across all skin tones.” (When I tested the Apple Watch on a co-worker whose skin was darker than mine, the results from the finger pulse oximeter also came out, but less so.)
Best also said, “For a small percentage of users, various factors may make it difficult to measure blood oxygen, including movement, positioning of the watch on the wrist, skin temperature and skin perfusion, and the dynamic feedback blood oxygen program to help users offers. Get the best study possible.”
The company sent me extra Apple Watch bands eight in total to wear while testing my second watch. This year, Apple is selling a new type of stretch band called the Solo Loop, which comes in a variety of sizes. Going down a size (to a model that leaves a slight impression on my wrist) removed some of the “measurement failed” error messages, but not all.
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