The Apple blood oxygen lawsuit is a patent fight between medical-device maker Masimo and Apple over the pulse oximetry sensor in the Apple Watch. Masimo has won an import ban that forced Apple to disable the feature in the United States, a Federal Circuit ruling affirming that ban, and a $634 million jury verdict for patent infringement. Apple restored the blood oxygen feature to U.S. watches in August 2025 through a software workaround that moves the calculation to a paired iPhone, and Masimo is now in court trying to shut that workaround down.
How the Fight Started
Masimo is an Irvine, California medical technology company that introduced its Signal Extraction Technology for noninvasive pulse oximetry in 1995. The technology uses light-emitting diodes and photodetectors against the skin to measure blood oxygen saturation.
According to Masimo CEO Joe Kiani’s 2023 Senate Judiciary Committee testimony, Apple approached Masimo in 2013 about integrating the technology into Apple products. Kiani said he shared information believing a partnership would follow. Instead, Masimo alleges, Apple hired away Masimo’s former Chief Medical Officer Michael O’Reilly, Cercacor’s former Chief Technical Officer Marcelo Lamego, and more than 20 other team members. O’Reilly left Masimo in July 2013 to work on what was then Apple’s “iWatch” project.1Respiratory Therapy. Apple Hires Former Masimo CMO2Becker’s Hospital Review. Masimo Sues Apple for Allegedly Stealing Health Monitoring Tech for Watch
In January 2020, Masimo and its spinoff Cercacor Laboratories sued Apple in the U.S. District Court for the Central District of California, alleging trade secret misappropriation and patent infringement. The case landed with Judge James V. Selna.3CourtListener. Masimo Corporation v. Apple Inc. That September, Apple launched the Apple Watch Series 6 with a blood oxygen feature. It became the product at the center of everything that followed.
The Import Ban
Masimo opened a second front in June 2021 by filing a complaint with the U.S. International Trade Commission, alleging that Apple’s importation and sale of Apple Watches with pulse oximetry functionality violated Section 337 of the Tariff Act of 1930.
On October 26, 2023, the ITC issued its final determination. It found that Apple had infringed claims of two Masimo patents — U.S. Patent Nos. 10,912,502 and 10,945,648, known as the “Poeze Patents” — which cover a user-worn device that measures blood oxygen using optical emitters and photodetectors. The Commission issued a limited exclusion order barring imports of infringing Apple Watch models with pulse oximetry functionality, along with a cease-and-desist order. Warranty service and repair of watches purchased before the ban were exempt.4U.S. International Trade Commission. Notice of Final Determination, Investigation No. 337-TA-1276
The practical result: Apple disabled the blood oxygen feature on Apple Watches sold in the United States.
Apple appealed. One of its main arguments was “prosecution laches” — that Masimo had unreasonably delayed by waiting from 2008 to 2020 to file the patent applications, making the patents unenforceable. On March 19, 2026, the U.S. Court of Appeals for the Federal Circuit rejected that argument, finding there had been “continuous prosecution activity” during the period, and affirmed the ITC’s determination in full.5IPWatchdog. Federal Circuit Affirms ITC Finding Apple Watch Infringes Masimo Blood Oxygen Patents6U.S. Court of Appeals for the Federal Circuit. Apple Inc. v. International Trade Commission, No. 24-1285 The Poeze Patents do not expire until August 2028.7Daring Fireball. The Return of Blood Oxygen for Apple Watch
The $634 Million Jury Verdict
The original California case moved on a separate track. A 2023 trade-secret trial ended in a mistrial after a hung jury. Masimo had accused Apple of using proprietary information obtained through the hired-away employees and had sought partial ownership of Apple’s resulting patents.8Fierce Biotech. Apple-Masimo Court Case Over Smartwatch Trade Secrets Ends Hung Jury
The patent claims went to a separate jury. On approximately November 14, 2025, a federal jury in California found that Apple had infringed a Masimo patent covering pulse oximetry technology — specifically U.S. Patent No. 10,433,776, which claims high and low heart rate notification — and awarded Masimo $634 million.9Healthcare Dive. Masimo-Apple Watch $634M Jury Award Patent Lawsuit10PatentlyO. Patient Consumer Wearable
Apple said it disagreed with the decision, calling it “contrary to the facts” and noting that “Masimo is a medical device company that does not sell any products to consumers.”9Healthcare Dive. Masimo-Apple Watch $634M Jury Award Patent Lawsuit Apple is fighting the verdict. As of February 2026, it was arguing before Judge Selna that Masimo had relied on an “improper and shifting definition of a dispositive term” at trial, and was pushing for judgment as a matter of law.11Law360. Apple Again Pushes to Escape Masimo’s $634M IP Verdict The case remained active with filings as recently as May 2026.12PlainSite. Masimo Corporation et al. v. Apple Inc. Analysts have estimated that if Apple ultimately appeals, the process could take up to two years.
How Apple Brought the Feature Back
Rather than wait for the courts, Apple engineered around the ban. In August 2025, it released iOS 18.6.1 and watchOS 11.6.1, which restored blood oxygen measurement on the Apple Watch Series 9, Series 10, and Apple Watch Ultra 2 in the United States.13Apple Newsroom. An Update on Blood Oxygen for Apple Watch in the US14Reuters. Apple to Bring Blood Oxygen Feature to Some US Watches With Software Update
The change is architectural. The watch’s sensors still collect raw data from the wrist, but the actual calculation of blood oxygen levels now happens on a paired iPhone. Results appear in the Respiratory section of the iPhone’s Health app rather than on the watch face itself. If the watch is out of Bluetooth range, the results are calculated once the devices reconnect.13Apple Newsroom. An Update on Blood Oxygen for Apple Watch in the US
That split matters legally. The Masimo patents describe a single device that measures, calculates, and displays blood oxygen data. By separating the functions across two devices, Apple argues the redesigned system falls outside the scope of the patent claims.15IPFray. Here’s How Apple Can Bring Back Pulse Oximetry in the U.S. U.S. Customs and Border Protection agreed. In an internal advice ruling (HQ H351038) issued August 1, 2025, CBP found the redesigned implementation did not violate the ITC’s exclusion order.7Daring Fireball. The Return of Blood Oxygen for Apple Watch Apple announced the update on August 14, 2025.
Masimo’s Suit Against Customs
Masimo responded within days. On August 20, 2025, it sued CBP in the U.S. District Court for the District of Columbia (Masimo Corp. v. US Customs and Border Protection, Case No. 25-cv-2749), seeking a temporary restraining order and a preliminary injunction to block the CBP ruling.16Bloomberg Law. Masimo Sues US Customs Over Apple Restoring Watch’s Oxygen Tool
Masimo’s complaint alleged that CBP had acted in an “arbitrary and capricious” manner by issuing the ruling ex parte, without notifying Masimo or letting it participate. That reversed an earlier January 2025 CBP decision that had required the blood oxygen feature to be disabled on imported watches. Masimo argued the new ruling violated the Administrative Procedure Act and the Due Process Clause of the Fifth Amendment, and “effectively nullified” the ITC’s exclusion order. Masimo also noted that CBP’s decision coincided with Apple’s August 6, 2025 announcement raising its U.S. capital investment commitments to $600 billion.17IPWatchdog. Masimo Challenges CBP’s Ex Parte Order Allowing Apple Restore Infringing Pulse Oximetry Function
By late August 2025, both CBP and the ITC pushed back, arguing Masimo was “seeking relief in the wrong places.”18Law360. CBP, ITC Say Masimo Suit Over Apple Watch Ruling Misplaced Separately, the ITC opened a combined modification and enforcement proceeding to resolve the conflicting CBP rulings on Apple’s redesigned watches, with a decision expected within roughly six months of late 2025.9Healthcare Dive. Masimo-Apple Watch $634M Jury Award Patent Lawsuit
What’s Still Open
Several pieces of the dispute remain unresolved as of mid-2026. The Federal Circuit has affirmed the ITC import ban, and the underlying Masimo patents run until August 2028.19Patent Lawyer Magazine. Apple v. Masimo: The Clash Over Pulse Oximetry Patents Apple’s redesigned blood oxygen feature is working on U.S. watches, but its legality depends on the ITC’s pending enforcement proceeding and Masimo’s suit against CBP. The $634 million verdict is still tied up in post-trial motions before Judge Selna and has not yet reached the appellate stage.11Law360. Apple Again Pushes to Escape Masimo’s $634M IP Verdict Apple’s own countersuit against Masimo in the District of Delaware, which asserts six Apple patents and which Masimo’s CEO has characterized as retaliatory, was also still active as of June 2026.20CourtListener. Apple Inc. v. Masimo Corporation No settlement has been announced.