How accurate is Samsung's Galaxy Watch for measuring blood pressure?

Samsung says its all-new Galaxy Watch will be able to measure blood pressure, which could be a big problem for doctors and consumers – but it's unclear how useful this feature will be.

High blood pressure is associated with an increased risk of heart disease, stroke, kidney disease and other conditions. Unfortunately, not only many people suffer from high blood pressure without knowing it, it is also difficult to accurately measure blood pressure because it varies tremendously at different times of the day and in response to different emotional and physical events. "If more people wearing watches are more aware of their blood pressure in general, that would be great," says Ann Marie Navar, a cardiologist at Duke University. An easy way to constantly monitor blood pressure would help patients check their stats between visits to the doctor. It could also allow researchers to better study the relationship between blood pressure and health.

It remains to be seen if the Samsung watch can do it. The company lacks details, but it seems that the watch will use an optical sensor to read blood pressure using a technique called Photoplethysmography (PPG), according to Wendy Mendes, a psychophysiologist at the University of California at San Francisco, who said helped Samsung develop 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 tissues (in this case, the fingertips), and then detects the amount of light returned. This amount of reflected light is related to changes in blood volume in the tissues and this information is transmitted to Samsung's My BP Lab application, where a proprietary algorithm interprets the results to estimate blood pressure.

On its own, PPG can only technically measure change in the blood pressure. This is why it is essential that users calibrate the watch's estimate with a real blood pressure reading at the doctor's office or one of these kiosks at Walgreens. "Calibration is really important," says Mendes. "It's like a scale. If I could not calibrate a scale, I might only be able to predict when it will go up and down. "

During a typical blood pressure reading, a doctor places an inflatable bladder tight around the arm to block the flow of blood. When the cuff is released, the doctor measures the points where the blood begins to flow again. This is the most common way to measure blood pressure without sticking a needle into the artery. It is more clinically accepted than a technique like PPG.

"This is where, as a clinician and researcher, I have a lot of concern," says Navar. "We need a lot more data on the accuracy of PPG compared to the usual methods of measuring blood pressure with external inflatable bladders." Many physiological factors could affect PPG signal strength, she says. This could be inaccurate for people who do not have high blood pressure, or for those with thicker or thinner arms.

For its part, Samsung has published very few details and has not responded to CNBC's inquiries regarding the integration of the third-party wireless wrist device, how often it should be calibrated, or how he validated the data. (In a statement to The edge, Samsung said it would share the details at a later date.) Mendes said his group was working on writing the validation study data, which involved 120 topics, and compared the application. to three sources of medical grade blood pressure. Another smart watch, created by Omron, uses the cuff method to measure blood pressure and was approved by the US Food and Drug Administration in December. However, it is unclear whether Samsung also plans to seek or receive FDA clearance.

The FDA is responsible for regulating medical devices, but said that "low-risk general wellness products" need not face the same scrutiny, according to Barbara Binzak Blumenfeld, a lawyer specializing in medical devices. approval of new devices and FDA regulation for the firm. Buchanan Ingersoll and Rooney. "For example, a product that claims to promote a healthier and more active lifestyle by monitoring heart rate would be considered a general wellness product," she wrote in an email, "while 39; a product such as the EKG of Apple Watch, more than promote a healthy lifestyle, must be a medical device. "

This divide between well-being and medical products is frustrating for cardiologists such as Bruce Alpert, who sits on the International Organization for Standardization's committee for blood pressure monitors. "US and international committee members are very frustrated because the term" blood pressure "is still a medical term," he says. "Among vital signs – such as heart rate and temperature – it is the only one that has a future predictive value for the severity or prevalence of the disease."

"There are a lot of new technologies that involve the rigidity of the artery or the behavior of it and many people have tried to translate that into a real blood pressure," says Alpert. "All these elements are valid from the point of view of physiology and, consequently, there are many different ways to shovel the cat. It's just a matter of: have they undergone, when developing their technology, proper tests to make sure what they call blood pressure is really a specific blood pressure? "

Navar agrees. "I really hope that one of these processes will go through a licensing process by the FDA, but to date, it has not yet been rigorously tested in any way. a way that, in my opinion, would be appropriate to replace an external measure inflated by the bladder, "she says. "It's a bit early to celebrate."