How To Monitor Blood Pressure Without Raising It

Does anyone actually enjoy the sensation of being squeezed by a blood pressure cuff? Well, as Mom used to say, it takes all kinds. For those who find the feeling nearly faint-inducing, take heart: researchers at UC San Diego have created a non-invasive medical wearable with a suite of sensors that can measure blood pressure and monitor multiple biochemicals at the same time.

The device is a small, flexible patch that adheres to the skin. So how does it manage to measure blood pressure without causing discomfort? The blood pressure sensor consists of eight customized piezoelectric transducers that bounce ultrasonic waves off the near and far walls of the artery. Then the sensor calculates the time of flight of the resulting echoes to gauge arterial dilation and contraction, which amounts to a blood pressure reading.

This patch also has a chemical sensor that uses a drug called pilocarpine to induce the skin to sweat, and then measures the levels of lactate, caffeine, and alcohol found within. To monitor glucose levels, a mild current stimulates the release of interstitial fluid — the stuff surrounding our cells that’s rife with glucose, salt, fatty acids, and a few minerals. This is how continuous glucose monitoring for diabetes patients works today. You can check out the team’s research paper for more details on the patch and its sensors.

In the future, the engineers are hoping to add even more sensors and develop a wireless version that doesn’t require external power. Either way, it looks much more comfortable and convenient than current methods.

16 thoughts on “How To Monitor Blood Pressure Without Raising It

    1. Otg: The text rendered in yellow here (on most browsers) are links to a pages with more information. Click on that block of yellow text in the first paragraph to see answers your questions.

  1. “Then the sensor calculates the time of flight of the resulting echoes to gauge arterial dilation and contraction, which amounts to a blood pressure reading.”
    It is, but, on the face of it, it would appear to be an uncalibrated one. Presumably a stiffer artery would give a lower BP reading? I have read some “stuff on the web” that says that one cause of increased blood pressure is arteries stiffening, which means that the body’s built-on pressure sensors become less sensitive. (Quotes as I have no idea if it is reliable information)
    This could probably be addressed by a conventional calibration test at the beginning and end of the test period, though.

    1. Interesting thought, certainly sounds like it should happen as you suspect. And all I can think of as a mitigation is the location it appears to be (assuming the above image is it in situ) – over the very largest vessel near the skin surface on the neck means any stiffening probably has smaller effect to calibration than if you are trying to read a much smaller vessel.

      Not sure if it matters that hugely though – if you are putting such a monitor in place its not for a one off reading – so as long as this shows trends correctly does it matter if the actual number it gives is meaningless?

      That said I’m no MD..

    2. “(Quotes as I have no idea if it is reliable information)” – Arteriosclerosis – “hardening” of the arteries. Yes, the condition increases blood pressure. FWIW sclerotic (scar tissue, in effect) carotid arteries can be the source of embolic strokes (think clots). Hemorrhagic strokes (ruptured artery -> internal bleeding) can result from the increased blood pressure as well. (remember the cartoons with a kinked hose…)

      Treatment differs in that embolic strokes may be treated with “clot-busting” drugs (TPA – in the first few hours. With hemorrhagic strokes medical management is challenged in that there is no simple way to apply pressure to the leak, so it’s mostly up to the body to control the bleeding inside the brain; outcomes tend to be more grim.

  2. I haven’t found a reference stating scientifically that sweat glands are capable of producing alcohol.

    This product sounds a little like the people from marketing/get-me-more-investor-money wrote up what it is capable of I’m afraid.

    1. Of course sweat glands don’t “produce” alcohol. But ingested alcohol perfuses throughout the water volume in a body, including the water that gets secreted as sweat. Alcohol passes just as easily out sweat glands as it does through alveoli.

      Don’t get any ideas though: just like you can’t breath your way to sobriety, you can’t sweat it out either, as it would involve sweating out all your body water too.

    2. From what I recall in regards to presence in the bloodstream… alcohol metabolizes into aldehyde by ADH and then acetate and if thoroughly intoxicated… ketone. Not certain… though guessing the sweat glands will excrete similar or the same.

  3. The sensor is really cool, but you’re a long way from useful product. If you’re measuring time of flight through an artery you’re going to need a great deal of signal processing. This Is a similar technique that is used in utility flow meters. Maxim and Texas Instruments both have ASICS for this, And they are surprisingly complex. In the flow meter example, time of flight is measured to sub nanosecond accuracy. Again not saying it’s impossible, but there still a long way to go before this device is actually useful. Still very cool.

    1. Time of flight measurement of arterial diameter is bog standard, almost trivial stuff. We were doing it routinely 25 years ago. You sure don’t need sub-nanosecond accuracy. A 20 MHz ADC (50 nanoseconds) and 5 MHz bandwidth is plenty. A sample at 20 MHz is 38 microns. To get as small as arterioles without scanning multiple lines, you probably want a bit better: maybe 80 MHz.

  4. And then you wake up in the middle of the night, suddenly feeling something in an odd place. Someone forgot to remove the sensor.

    I had 2 or 3 electrocardiograms two years ago, and every time, this happened. Of course, a lot more sensors involved.

  5. This is for me. My family has a history of heart issues so I get checkups from 30 years of age. I seem to have something they call White coat syndrome (translation from Dutch). When I am in a medical environment and my blood pressure get measured it is dangerously high.
    What works now is a wearable blood pressure sensor that inflates every 30 minutes or so amd it has to be worn for 24 hours. This is really uncomfortable while working even more when trying to sleep. Luckily after a few hours my blood pressure seems to be ok.

    I would like this sensor for a week every 1 or 2 years.

  6. “To monitor glucose levels, a mild current stimulates the release of interstitial fluid — the stuff surrounding our cells that’s rife with glucose, salt, fatty acids, and a few minerals. This is how continuous glucose monitoring for diabetes patients works today.”

    No. They almost universally use a cannula. This free book is the best source of info on noninvasive glucose measurement by someone that chased every product. Smith points out that glucose is polar but does not ionise easily, so using a current to push it through a membrane out of the body – reverse iontophoresis – works badly.

  7. Would this work for Dogs ?

    I’ve husky sled team, i’ve been looking for a non-invasive way of health monitoring them during their run. I had looked at the clip on ear they use during operations but with the joggling about from them running it would need to be so tight as to be painful for them

  8. Do they need testers? I have Addison’s disease and I am constantly checking my blood pressure. When my blood pressure goes down it happens very fast. It would be great to know it was stating to go down so I could take my medicine before it caused me to pass out. If they do need testers, I would love to be one!! I am 50 years old and pretty healthy other than my Addison’s disease and back issues. Diabetes does run hard in my family, both parents and my sister have it. I am very interested in this!!

  9. Neat sensor design. Reads like the OpenWater Company is even utilizing ultrasonic methodologies now. Little bit challenging to perform for those who have no sweat glands or maybe a few like at the palms or pads. Wondering what AI algorithms can further optimized analysis with the traditional struggling contactless sensing, and new not so well detailed RF/microwave wireless, methods?

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