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What if there were a wearable fitness device that could monitor your blood pressure continuously, 24 hours a day?
Unfortunately, blood pressure (BP) measurements currently require the use of a cuff that temporarily stops blood flow. So a wearable BP "watch" using today's technology would squeeze your wrist every few minutes, making it impracticable to use – not to mention annoying.
A better method might 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. But before scientists can create this new technology, they need to understand what the pressure inside a blood vessel "looks" like on the surface of the skin. And to do that, they must make a physical model that can be used to test wearable devices in a laboratory.
NIST's Physical Measurement Laboratory (PML) is currently collaborating with Tufts University's School of Medicine to develop just such a model, a blood pressure wrist "phantom" – essentially a fake arm that mimics the mechanical properties of blood pulsing through an artery surrounded by human tissue.
All watches are not wearable?
(Score: 0) by Anonymous Coward on Tuesday January 31 2017, @04:43PM
But before scientists can create this new technology, they need to understand what the pressure inside a blood vessel "looks" like on the surface of the skin. And to do that, they must make a physical model that can be used to test wearable devices in a laboratory.
Which means they have nothing.
As someone that has modeled blood flow in various body vessels, let me tell you that "state of the art" for modeling this doesn't really exist. And trying to fit this into a model is going to be quite hopeless for number of reasons.
1. vasoconstriction will affect how a vessel like artery looks like from outside. There are *many* factors that affect this, from your diet to your state of mind to ambient temperature to your recent activity level.
2. arteries are not "pipes" - they are muscles.
3. flexibility of the artery is mostly unique to an individual at a given point in time (age and time of day and diet and the rest ;)
So, what is the gold standard? You stick a needle into an artery to measure your blood pressure directly. Probably not great idea for a watch. Using blood pressure cuff to mechanically obstruct the pressure is 2nd best option. Heck, for people with high blood pressure on the lung side, the only reliable way of measuring blood pressure is catheterization (unless something changed in last decade?) since there is no access to pulmonary artery. And ultrasound doesn't give you pressure measurement.
Measuring sugar content or oxygen saturation is easy - you just stick a spectrometer on your finger. Pulse is tricky enough and that can be measured directly. But indirect pressure measurement? Right... good luck with that!