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SergeantQueen's avatar

How would a watch measure blood pressure and blood oxygen?

Asked by SergeantQueen (11169points) 2 weeks ago

It is a $40 ish dollar watch. Just flashes green and gives me numbers? I tried looking at the FaQ but it doesn’t make much sense. It also tracks heart rate.

The FaQ only talks about the heart rate. Here is the answer to “What does the green light do?”

“The green lights are used for monitoring your heart rate.The way this is done is through a process called photoplethysmography. The green light shines into the skin where your blood cells are passing by the area. There is an optical sensor that detects the passage of blood and then estimates a heart rate.”

Could this also be how they do the blood pressure + oxygen levels? I got this watch to track my sleep + steps, so this feature seems cool but also shady.

this is the watch

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12 Answers

Patty_Melt's avatar

I wouldn’t trust it for those two functions either.
Might be fun to check out though, if you are happy enough with the other functions.

Call_Me_Jay's avatar

Blood pressure is not among the features listed for the watch.

LuckyGuy's avatar

Unless it has a tight band and has some form of automatic tightening it cannot measure blood pressure..That claim is bogus.
However, it theoretically it can measure blood oxygen level and heart rate.

Blood is a very clever material. It changes color depending upon the presence or absence of oxygen. Look at your veins. They are blue because your body used up the oxygen carried in the blood changing its color to blue. That blood is pumped by the heart into the lungs where it is oxygenated again and turns red. That is why your arteries are red. They are filled with freshly oxygenated blood ready to do work.
Now look at that magic green light. Caution: there are different designs so this might not be exactly how your works. That green light is a laser diode or LED that actually emits 2 wavelengths, the green that you see and an infrared that you don’t see. If you look closely and move your eyes around you will see it is also flashing at a high frequency.
By looking at the ratio of the reflected light into the nearby detector it can see the color of your blood. By looking at the rate of change of the absorption it calculates the heart rate.
You can buy pulse oxcimeters for about $20—$30 that work really well.

Tropical_Willie's avatar

“Heart Rate Monitoring & Sleep Tracking: Automatically monitor your daily real-time heart rate, and track your sleep quality status to get a better understanding of your health ”

No mention of Oxygen or B/P functions.

gondwanalon's avatar

My “Bakeey V19” blood pressure measurement is pretty precise but not so accurate.

The V19 is consistently a little high for blood pressure arm sphygmomanometer reading this morning was 107/68 and the VP reading was 111/81

The V19 also measures time, O2, heart rate, steps per day, sleep quality and quantity, and an ECG. The ECG is pretty crappy but the other aspects are pretty accurate. How it functions with the green light on the wrist is a mystery to me.

I bought my V19 from eBay for $24 with free shipping.

Call_Me_Jay's avatar

In the hospital they use a fingertip oxygen reader that also simply shines a light at your skin. It’s definitely a legit way to go.

Regarding heart rate, I have a five year old Fitbit Charge HR which measures with a green LED. It’s pretty accurate when sitting still (I used a stethoscope and watch to test the accuracy).

I was thinking about replacing it in the fall and from what I gather, Letscom is a decent brand, and the $30—$40 fitness trackers are a great buy. I would recommend it over a Fitbit because of the price.

SergeantQueen's avatar

The watch doesn’t say it on Amazon but it is a feature on the watch. I can click and have it measure it. I think it isn’t very accurate, either.

Call_Me_Jay's avatar

Blood pressure? Interesting.

LuckyGuy's avatar

@gondwanalon How does the watch know when it is at the same level as your heart? Position makes a big difference. It’s a basic hydraulics problem.

JLeslie's avatar

@LuckyGuy The person knows if they are in the right position or not. No matter what a person uses to take their blood pressure they need to be aware of their position.

Caravanfan's avatar

That particular watch you linked to does not measure blood pressure or blood oxygen level.

SergeantQueen's avatar

It is the same one I bought (from my recent orders list) and it does so I am very confused now

Nevermind, I see what I did wrong. I’ll link the one I bought later.

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