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How exactly can the Samsung Galaxy Watch measure blood pressure?

Samsung says its latest Galaxy Watch can measure blood pressure, which could be a big deal for doctors and consumers alike – but it's still unclear how useful it actually is.

High blood pressure or high blood pressure is associated with an increased risk of heart disease, stroke, kidney disease and other disorders. Unfortunately, not only do many people have high blood pressure without knowing it, accurate blood pressure measurement is difficult because it changes so much at different times of the day and in response to various emotional and physical events. "If more people who wear watches know their blood pressure generally better, that would be great," says Ann Marie Navar, cardiologist at Duke University. An easy way to continuously monitor blood pressure would help patients to check their values ​​between visits to the doctor. It could also allow researchers to better study the relationship between blood pressure and health.

Whether the Samsung watch can do this is still an open question. The company has too few details, but it appears that the watch will use an optical sensor to measure blood pressure using a technique called photoplethysmography (PPG), says Wendy Mendes, a psychophysiologist at the University of California San Francisco, who Samsung has assisted in the development of the tool.


This feature has been around for a year on the Samsung Galaxy S9. The Galaxy S9 phone has an optical sensor that illuminates the tissue (in this case the fingertips) with light and then detects how much light is bouncing back. This amount of reflected light is related to changes in blood volume in the tissue, and this information is sent to Samsung's My BP Lab app, where a proprietary algorithm interprets blood pressure estimation results.

PPG alone can measure [] only blood pressure changes . For this reason, it is important for users to calibrate the watch's estimate with the actual blood pressure readings in the doctor's office or one of these Walgreens kiosks. "Calibration is very important," says Mendes. "It's like a balance. If I could not calibrate a balance, I might just be able to predict when it will go up and down. "

In a conventional blood pressure measurement, a doctor places a tight inflatable bladder or cuff around the arm to block the blood flow. When the cuff comes off, the doctor measures the points where blood flows again. This is the most common way to measure blood pressure without putting a needle in the artery, and is clinically more acceptable than a technique like PPG.

"As a clinician and researcher, I have many concerns," says Navar. "We need to see much more data on the accuracy of PPG compared to the standard methods we use to measure blood pressure with external inflatable bladders." Many physiological factors could affect the strength of the PPG signal, she says. This may be inaccurate in people without hypertension or in thicker or thinner arms.

Samsung, for its part, has released very few details and has not responded to CNBC inquiries as to whether the device can be integrated into third-party wireless cuffs, how often it needs to be calibrated, or how the data was validated. (In an Opinion on The Verge, Samsung said that Samsung will provide details at a later date.) Mendes said her group is working to write data from the validation study, which involved 120 subjects, and compared the app to three different sources of medical blood pressure. Another Omron smartwatch uses the cuff method to measure blood pressure and was approved by the US Food and Drug Administration in December. However, there is no word as to whether Samsung also wants to apply for FDA or seek approval from the FDA.

The FDA is responsible for the regulation of medical devices, but has stated that "low-risk general health products" do not have to face the same test, said Barbara Binzak Blumenfeld, a lawyer specializing in the approval of new equipment and has specialized in the navigation of FDA regulations for the company Buchanan Ingersoll & Rooney. "For example, a product claiming to promote a healthier, more active lifestyle by monitoring heart rate would be considered a generic wellness product," she wrote in an e-mail, "while a product like the Apple Watch ECG should do that." More caring for a healthy lifestyle has to be a medical device. "

This gap between wellness and medical devices is frustrating for cardiologists like Bruce Alpert, who is a member of the International Organization for Standardization of Sphygmomanometers." We in the United States and international committees are very frustrated because the term "blood pressure" is always a medical term for us, "he says." Of the vital signs – such as heart rate and temperature – this is the only one predictive of future Has value for the severity or prevalence of disease. "

" There is a tremendous amount e Number of new technologies that affect the stiffness of the artery or the way The artery behaves and many people have tried to translate it into real blood pressure, "Alpert continues. "All of these factors are physiologically valid and therefore there are many different ways to skin the cat. It's just a question of: Did you take appropriate tests in the development of your technology to make sure that blood pressure really is blood pressure? "

Navar agrees. "I really hope one of them goes through an FDA clearance process, but so far it has not been tested in a way that I think is likely to replace an external bubble-inflated measurement," she says , "To celebrate it is still too early."

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