Here's one big reason I'm sticking with my Apple Watch Series 7 and forgoing the Series 10

Some new features make the new Apple Watch Series 10 an attractive prospect, but my old Apple Watch Series 7 has one notable thing that Apple's new smartwatches lack: blood oxygen tracking. This is enough to keep me happy with my older model.

The blood oxygen monitoring feature is only available in the Apple Watch Series 6, 7, 8, and the Ultra released in 2022. Notably, Apple is now releasing the Apple Watch Series 10 without the feature in the US.

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Apple removed the blood oxygen capability in the US in January 2024, just a few months after the release of the Watch Series 9 and Watch Ultra 2 a year ago.

A patent lawsuit with Masimo brought about the removal. The highly publicized dispute resulted in the US International Trade Commission (ITC) ruling in October 2023 that the Apple Watch Series 9 and Ultra 2 infringe Masimo's patents for pulse oximeters. The ITC banned the sale of new models with this feature in the US -- the rest of the world still has access to it.

Apple disabled the blood oxygen monitor in the new smartwatch models, which allowed the tech giant to continue selling the Series 9 and Ultra 2 without pulse oximetry.

Blood oxygen tracking measures oxygen saturation in the wearer's blood by using light sensors and shining red and infrared lights, then assessing how light is absorbed through the blood. The oximeter analyzes light absorption to estimate the amount of oxygen in the blood, as oxygen-rich blood absorbs more infrared light and reflects more red light.

Masimo alleges that Apple used its patented methods for measuring oxygen levels through light-based sensors and algorithms to analyze light absorption in the blood. Masimo had designed and patented this technology for medical-grade blood oxygen sensors but claimed Apple used them in its consumer products without proper licensing.

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When it came time to announce a new lineup of Apple Watch models during the "It's Glowtime" event, Apple focused on other health-tracking features in the new Apple Watch Series 10, now available for pre-order, avoiding the blood oxygen subject altogether.

Instead, Apple touted its new sleep apnea monitoring feature, which uses sleep data captured by the watch and combines it with a new measure that employs the accelerometer to detect breathing disruptions, a telltale sign of sleep apnea.

The blood oxygen feature was very popular on the Apple Watch. While the pulse oximetry in the Apple Watch isn't as accurate as that of medical-grade devices, some medical studies have found it tends to be within acceptable limits, considering it's not meant as a diagnostic tool.

As an Apple Watch Series 7 user, I am lucky to still have access to the pulse oximetry feature. I like checking my blood oxygen and seeing how it trends over time and with different life changes, like adopting a new exercise regimen. Plus, since I am at high risk for lung disease due to an autoimmune illness, the SpO2 measurements serve a double purpose in my life.

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To be clear, the Apple Watch Series 9 and Ultra 2 still ship with the oximetry sensor, as will the Apple Watch Series 10. The feature is only banned for Apple Watches sold in the US, so the rest of the world can still access blood oxygen monitoring on the Series 9, 10, and Ultra 2. Apple is expected to continue working towards bringing back the pulse oximetry feature, which is partly why it was only half surprising not to see it reintroduced during the latest iPhone event.

Apple is also reportedly working on adding blood pressure monitoring to its smartwatches, though that'll likely come in the Apple Watch Series 11 or later. Blood pressure tracking works differently on a smartwatch than oxygen tracking, though both use similar photoplethysmography (PPG) sensor technology. Blood pressure requires PPG and ECG to measure pulse transit time or heart activity.