There may be much more on the roadmap for the Apple Watch than people realize. A recent patent filed by the Cupertino company describes a clever way of using existing technology in its smartwatch to calculate blood pressure.
Often called the “Silent Killer”, one in three adults are affected by high blood pressure. As many as a third of these are, however, unaware they have a problem. The only way to know what your blood pressure is, is to have it measured. Right now Apple Watch alone cannot take a reading.
Essential reading: Top smart blood pressure monitors
There is a wide range of smart blood pressure monitors that can do this. To calculate a reading, such devices stop the blood flow in your veins by inflating a blood pressure cuff around your upper arm or wrist, and then listen to changes in your arteries. Despite some claims, there is no clinically proven accurate way to measure blood pressure from the current crop of fitness trackers and smartwatches.
But all this may change soon.
Uncovered by Patently Apple earlier this week, Apple’s filing was published by the U.S. Patent and Trademark Office in the first quarter of 2017. As it refers to “wrist-worn devices” a number of times, it is probably safe to assume Apple is talking about its smartwatch.
The basic idea is to use something called pulse transit time (PTT) to calculate on-demand readings of your blood pressure. This is a way of taking measurements by timing how long the pulse travels from a person’s heart to their wrist.
Users would place their watch against their chest so that the accelerometer detects the user’s heartbeat. The heart-rate sensor in the device would then calculate the PTT by detecting when the blood pressure pulse arrives at the wrist. How precise such a method would be remains to be seen, but if accurate it could be a game-changer.
“Wrist-worn devices and related methods measure a pulse transit time non-invasively and calculate a blood pressure value using the pulse transit time. A wrist-worn device includes an accelerometer, a photo-plethysmogram (PPG) or a pulse pressure sensor, and a controller,” Apple notes in its patent filing.
“The PPG or the pulse pressure sensor coupled to the wrist-worn device for detecting an arrival of a blood pressure pulse at the user’s wrist. The controller is configured to process output signals from the accelerometer to detect when the blood pressure pulse is propagated from the left ventricle of the user’s heart, process a signal from the PPG or the pulse pressure sensor to detect when the blood pressure pulse arrives at the wrist, calculate a pulse transit time (PTT) for propagation of the blood pressure pulse from the left ventricle to the wrist, and generate one or more blood pressure values for the user based on the PTT.”
There’s no information on when this new blood pressure tracking method could make it into a consumer wearable. Apple files numerous patents each year and many of them do not see the light of day.
The company’s job will be made easier thanks to changes introduced last month by the FDA. The agency is working with Apple and 8 other major tech companies on a program designed to assess if its possible for a select group companies to submit less information when seeking market approval for a new health gadget. It is even be possible that some products could skip this process all together.
You can read the full patent application on this link.
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