Fitbit is developing a tiny blood pressure monitor for its smart watch

Fitbit has registered a patent application in the US for an in-watch blood pressure sensor

The patent documentation was created by Shelten Yuen, Fitbit’s VP of research

It combines a force sensor (pressed by a user’s finger) and PPG sensor that work together to calculate a blood pressure reading

In April 2021, US Fitbit users took part in a month-long blood pressure tracking study led by Yuen

Google-owned Fitbit has has filed a patent application with the US Patent and Trademark Office for a blood pressure sensor that will be in-built into its smart watches.

The application was made by Shelten Yuen, Fitbit’s VP of research who joined Fitbit in 2007 with a background in surgical robotics. It describes a wrist wearable with a force sensor and PPG (Photoplethysmography) sensor, which uses light to give a heart rate reading. These work together to calculate blood pressure.

Blood pressure is one of the holy grails of wearables and, as fit tech businesses compete to become the top choice of consumers, more are looking to add it.

The Fitbit application shows that the user’s finger would need to press on a force sensor in order to record their blood pulse amplitude.

Typically, blood pressure is taken using a traditional cuff to cut off the circulation and then record the flow of blood as it loosens, measuring the strength of the person’s heart beating against the pressure.

Blood pressure is measured in units of millimeters of mercury (mmHg) – it is considered normal to have a systolic value (pressure in the arteries as the heart beats) under 140 mmHg and a diastolic value under 90 mmHg (pressure in the arteries between beats).

Blood pressure checks were traditionally only available through a visit to the GP or hospital, however home-testing has become far more widespread as companies such as Omron have brought accurate consumer devices to market and Fitbit has been hatching plans to make blood pressure readings part of everyday life via wearables for some time.

In April 2021 – a few months after Google acquired Fitbit – US Fitbit users were asked to sign up to a month-long blood pressure tracking study. It was looking at how Fitbit devices can measure Pulse Arrival Time (PAT), defined as the “time it takes for a pulse of blood to reach your wrist after your heart beats”, to investigate a potential link to tracking blood pressure. The company said that results would be used for “future product development”. This testing has been part of the development process leading up to the patent application.

“If high blood pressure was easier to measure, people could manage it earlier, which might help avoid preventable deaths from heart disease and stroke,” said Yuen at the time, who was leading the project. “It’s a hard scientific challenge, and a lot of work remains to be done to understand the best way to do this, but we have a history of advancing technology to make previously inaccessible health metrics available to Fitbit users from their wrist, so it’s a challenge we’re very passionate about solving.”