A US appeals court has backed a challenge launched by Apple at the US Patent and Trademark Office that had found medtech company Masimo’s patent claims relating to blood oxygen measurement unpatentable for obviousness.

Apple had argued successfully in its inter parties review petition at the Patent Trial and Appeal Board (PTAB) that the claims were unpatentable because, among other things, it would have been obvious over the prior art.

The opinion by the Court of Appeals for the Federal Circuit on 10 January, affirms this, with circuit judges Lourie, Prost and Reyna finding Masimo’s arguments to the contrary “unpersuasive” and two claims in Masimo’s patent relating to blood oxygen measurement unpatentable for obviousness.

Masimo had argued that PTAB’s use of the words “could” and “reasonable” showed that it applied an incorrect legal standard for obviousness.

The judges, said, however that throughout the PTAB’s decision “it made findings about what a person of ordinary skill in the art would have been motivated to do, not simply what the person could have done”.  

The patent covers pulse oximter technology that measures oxygen in the blood used in some models of Apple watches. 

Apple is facing an import ban on certain models of Apple Watches after the International Trade Commission found in October that it had violated US laws by incorporating Masimo’s patented light-based pulse oximetry technology in its products.

Apple is appealing the ruling, and as of 27 December, the ban had been temporarily paused allowing sales of watches to resume in Apple stores and on its website in the US.

Masimo was represented by California-headquartered IP firm Knobbe Martens Olson & Bear’s Jeremiah Helm, John M Grover, Stephen C Jensen, Shannon Lam and Joseph R Re. Apple was represented by IP law firm Fish & Richardson’s Lauren Ann Degnan, Michael John Ballanco, Walter Karl Renner and Robert Courtney.