Measuring blood pressure through a fitness tracker is a relatively new feature that tracker companies are just starting to develop. Though there may not be many options for blood pressure monitoring trackers, there are some on the market, and they are getting more and more accurate. 

So how do fitness trackers measure blood pressure? There are three main methods to finding out your blood pressure through fitness trackers. The most accurate is through traditional cuff inflation, with photoplethysmography (PPG) at a close second, or, a little less conveniently, from external devices. Read on for more information about each method. 

Cuff

Currently, there is one smartwatch fitness tracker on the market that uses an inflatable cuff at the wrist to measure blood pressure and that is the Omron Heartguide. You can find out a little more about the Heartguide here

Many argue that measuring blood pressure using the cuff method is the most accurate way to do it. This claim is substantiated by the FDA, since the Omron Heartguide is the only smartwatch approved to check blood pressure, though other smartwatches and fitness trackers have blood pressure tracking listed among their features. 

However, just because Omron is the only one approved to check blood pressure accurately, doesn’t mean that some of the other fitness trackers aren’t accurate if used correctly. The technology for photoplethysmography PPG is still fairly new; if you don’t have a heart condition, you may want to compare one of the PPG trackers against a blood pressure monitor to check accuracy. 

If you do have a heart condition, then the best route to take would be to ask your physician for advice, or bring your tracker in to the doctors office to compare it with your physician’s reading. 

Photoplethysmography (PPG)

The technology that is used in most fitness trackers that claim to read blood pressure is photoplethysmography or PPG. This process is technical but simply put, the device emits a light and measures the reflection of this light to, in turn, measure the blood volume. According to the National Center of Biotechnology Information, the device will emit an infrared light to measure the blood flow deep in the tissue or muscles. If the device emits a green light, it is commonly measuring the absorption of oxygen in the blood (NCBI). 

This is the technology that is used in finger cuffs that you may have used at the doctors office. It does an alright job, but it is not accurate enough for most doctors to use say, during a surgery.

This is also the technology that is used in many fitness trackers that claim that they record blood pressure. It is not technically blood pressure, but the measurements are correlated enough to replace a blood pressure measurement. 

External Devices

If you aren’t the type of person who wants to have a wrist cuff inflating on you several times in a day, but you do want to have the most accurate blood pressure readings possible, then an external blood pressure device might be just what the doctor ordered–literally. 

There are several blood pressure monitors on the market currently that will pair with your phone or smartwatch either with a cord or through bluetooth, making sure that all your information is in the right place. 

The wrist is arguably not the best place for measuring blood pressure. The arteries are very small and the bones can also get in the way of the most accurate reading. This is why most doctors prefer to take your blood pressure on your upper arm where the arteries are thicker and a cuff can apply more pressure. 

So if you are planning on tracking your blood pressure because you have a mild curiosity about how your fitness level is affecting it, you’ll probably be just fine with the PPG method of measuring blood pressure. If, however, you have a heart condition already, you may want to invest in one of the external devices, or even do both to measure the accuracy against each other. 

Why Is Ambulatory Blood Pressure Beneficial?

Your blood pressure is arguably the most important aspect of your health to monitor. This is because it is a preliminary symptom of hardening of the arteries, stroke, kidney disease, or heart attack. 

The American Heart Association states that “High blood pressure is a largely symptomless ‘silent killer.’ If you ignore your blood pressure because you think a certain symptom or sign will alert you to the problem, you are taking a dangerous chance with your life” (AMA).

Office Monitoring Is Not Enough

Many people who have “white coat hypertension” or get overly nervous at doctors appointments resulting in high blood pressure, are recommended to use ambulatory blood pressure monitoring. This is a portable blood pressure cuff that the patient can wear throughout his or her daily activities to give his or her physician a 24 hour period of time of regular monitoring. 

The measurement that a doctor gets in the office is meant to be a resting blood pressure, and whether you get nervous around doctors or you simply had to rush to get to your appointment, your blood pressure could be much higher than what your daily average might be. 

This is why ambulatory blood pressure monitoring is the preferred method of getting an accurate reading of blood pressure if your doctor is determining to diagnose you with hypertension. An average of your blood pressure readings throughout the day, including periods of exercise and sleep, is the most accurate way to measure your blood pressure and your overall health. 

With heart disease the leading worldwide cause of death, and high blood pressure the leading indicator of heart disease, blood pressure is more important than ever to monitor. Therefore,  having a blood pressure monitor on your fitness tracker should be an important feature that you look for. 

Why Are There Not More BP Fitness Trackers?

If you search for fitness trackers that measure blood pressure, you don’t come up with too many immediate results. 

Why is this? One of the primary reasons why there aren’t very many trackers that measure blood pressure, in the US at least, is since fitness trackers deal with your health, they have to pass certain FDA approved regulations. There are some on the market that have been deemed acceptable, but not recommended. 

There is only one BP fitness tracker that is currently passed by the FDA, the Omron Heartguide, and you can find that right here

Though the wrist is currently not an ideal place to measure blood pressure, and you will get a more accurate reading on your upper arm, technology is only getting better with time, and there may be a day in the very near future where blood pressure monitoring from the wrist in fitness trackers is commonplace.  

New Technology

Many people want to measure their blood pressure regularly, if not continuously, but very few people want to deal with the inconvenience of having an inflatable cuff on their wrist cutting off their blood flow every 15 to 30 minutes. Even with the Omron Heartguide, you do have to stop what you’re doing and hold your wrist at heart level to get an accurate reading. 

Right now, a fitness tracker with an inflatable cuff, is a good idea, but still impractical for frequent everyday use. This is why scientists are working on a new technology that doesn’t require an inflatable cuff or an infrared light to get a blood pressure measurement. According to the National Institute of Standards and Technology US Department of Commerce (NIST), cuffless accurate blood pressure monitors may not be far off. 

The NIST explains that scientists are working on a blood pressure monitor, that instead of inflating, will “gauge subtle pressure changes at the surface of your skin above one of the main wrist arteries – the radial artery – without regularly cutting off your circulation” (NIST). 

The challenge with this method of measuring blood pressure, other than it has never been done before, is that the scientists have to create a model that mimics arteries in the wrist to test it, which they have done using a 3D printer. 

They use a silicone pad to mimic the tissue of an arm and have a fake artery running through it. Then they use sensors to record data as different weights are pulsed against the silicone. In this controlled environment, they can see how accurate their measurements are and what kinds of readings the sensors are picking up. This technology still has some work to go, but could be ready for a prototype in the near future. 

Conclusion

The technology for measuring blood pressure is advanced as it stands now, but still flawed. There is definitely room to grow and, in an overly saturated market of fitness trackers, it will be interesting to see which companies pursue developing this technology to stand out from the crowd. Blood pressure is a vital part of overall health and the technology to monitor it accurately will prove to be worth the effort of developing. 

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