The USITC has started a new investigation looking at the Apple Watch, to see if the blood oxygenation sensing changes implemented earlier in 2025 still infringe patents held by medical tech company Masimo.

On Friday, the US International Trade Commission (ITC) issued an order to restart an investigation about Apple Watch, and the potential violation of Masimo's patents. This time, the investigation is looking at Apple's software work-around.

Back in 2023, the ITC found that the Apple Watch Series 9 and Apple Watch Ultra 2 models infringed Masimo's patents over blood-oxygen measurement technology, and blocked their import.

In response, Apple removed the blood-oxygen sensing feature. Apple then subsequently re-introduced an updated version of that capability in August 2025 following U.S. Customs approval.

Masimo contends this re-introduction still violates its patent rights and is suing U.S. Customs in a separate action. Apple has challenged the ITC ban in federal appeals court.

The new investigation by the ITC, entered into the federal registry on Friday, is expected to be complete before April 2026.

He-said, she-said

According to Masimo, Apple met with U.S. Customs on August 1, 2025 to secure approval for re-enabling the blood-oxygen feature, Masimo argues that they had no idea that this was going on, and bypassed due-process protections.

Apple offloaded some of the processing to the iPhone, and argued the updated system was sufficiently different to side-step the earlier infringement ruling. Masimo claims it only learned of the feature's return when Apple publicly announced it — not via prior notice or negotiation.

If the ITC determines the new Apple Watch models continue to infringe Masimo's patents, U.S. imports could again be banned. This will impact Apple's supply chain and timelines, and the availability of key features in the U.S.

Obviously, the blood-oxygen sensing capability is a flagship wellness feature for the Apple Watch lineup. The feature is presently enabled, executing the analysis differently, after more than a year of it being shut off in software on devices manufactured or imported after the ban.

Here we go again...

Apple is facing another round of risk with the Apple Watch over Masimo's blood-oxygen sensing patents, which we expected would happen sooner or later. While the feature is currently enabled, it may yet be subject to disruption depending on how the ITC and courts rule in 2026.

And while this has happened, the CEO who started this all, Joe Kiani, stepped down after being removed from Masimo's board by shareholders. The move came after a proxy battle with hedge fund Politan Capital Management.

The battle ensued after a $1 billion acquisition of Sound United, which pushed Kiani out. Politan nominated key board members, one of whom is now interim CEO, Michelle Brennan.

Kiani said in live appearances that he was waiting for Apple's call to deal with the matter on numerous occasions. Apple said that they reached out, but was mostly rebuffed by the CEO at the time.

It's not clear if Apple has had further discussions with Masimo or the new CEO after the Apple Watch blood oxygen sensing was restored.