Apple investigating using Apple Watch to continually measure blood pressure

Posted:
in General Discussion edited November 2020
Instead of the periodic or on-demand measurement of heart rate that the Apple Watch can currently do, future devices may provide constant monitoring.

Participants were required to wear Apple Watch for at least five hours per day over an extended period
Future Apple Watches may be able to measure blood pressure as well as heart rate


Perhaps the very first health feature of the Apple Watch was its ability to sense heart rate. Five years and six versions on, it's still a key feature -- and Apple continues to research how to add blood pressure measurements to it.

A pair of newly-revealed patent applications show that Apple wants to make it possible for the Apple Watch to continually monitor blood pressure. "Electrical Coupling of Pulse Transit Time (PTT) Measurement System to Heart for Blood Pressure Measurement," says that it can be done without interruption to the user.

"Current ambulatory and home blood pressure measurement approaches... fail to provide continuous measurement of blood pressure," it says. "Additionally, when an oscillometric blood pressure measurement cuff is used to monitor a person's blood pressure when sleeping, the intermittent inflation and deflation of the cuff can disturb the person's sleeping pattern, thereby harming the subject to some extent and potentially changing the person's sleeping blood pressure."

"Thus, convenient and effective approaches for noninvasive continuous measurement of blood pressure remain of interest," it continues.

Both this, and the similar "Blood Pressure Monitoring Using a Multi-Function Wrist-Worn Device" patent application, propose using the Watch as just one part of the process. In each of these new applications, the Watch will measure blood pressure by timing how long it takes a pulse to reach it from the user's heart.

"Output from a pulse arrival sensor coupled to the wrist-worn device is processed to detect when a blood pressure pulse generated by ejection of the volume of blood from the left ventricle arrives at the wrist," says the first patent application.

"A pulse transit time (PTT) for transit of the blood pressure pulse from the left ventricle to the wrist is calculated," it continues.

This does mean the user wearing electrodes or some other kind of sensor as well as the Apple Watch. So it's not going to be adopted by everyone, it will be used when medical advice recommends continuous study.

Detail from the patent showing positioning of sensors
Detail from the patent showing positioning of sensors


"Home blood pressure measurements may be recommended where information is desired regarding the effectiveness of blood pressure lowering medication," explains Apple, "and/or where doubt exists as to the reliability of ambulatory blood pressure measurement."

Apple has previously investigated doing continuous heart rate measures without the use of extras such as electrodes, or a blood pressure cuff.

Comments

  • Reply 1 of 17
    An Apple Watch with this feature would would be one that I’d gladly upgrade to.
    neo-techtwokatmewiHymontrosemacs
  • Reply 2 of 17
    GeorgeBMacGeorgeBMac Posts: 10,298member
    This would be great! 
    Most physicians now agree that in-office blood pressure is less than accurate -- not only are they dealing with "white coat syndrome" but even variations in how different people take it.   I cringe when a nurse with a dime store stethoscope uses an 8" cuff on my arm -  it guarantees a bad reading.    For myself, when I was working in a hospital I started using only machine readings to help smooth out the variations between how different staff recorded it.  (One would think they would know how to do it, but...)

    The consensus is swinging over to at least considering, if not relying on, mobile (home based) measurements.
    My own (bad) experience with office based measurements was when I saw a PA in a cardiologist's office and, right before taking my blood pressure, she started nagging me about something contentious.   My pressure came out 20 points higher than normal!

    But, as a nurse one experience was eye opening:   when working in a children's hospital I took a kid's pressure but for some reason my instincts told me to recheck it and the second reading came out much higher.  So I took it again and the reading was much lower.   After the repeating the process a few times I realized it wasn't bad readings but the kid's pressure was fluctuating all over the map with wide swings up and down.   I immediately notified one of the doctors and within minutes the kid's bed was surrounded by half a dozen physicians and a very short while later he was down in the ICU.   I never heard what happened to him after that but always wondered.

    Continuous, accurate monitoring would be a marvelous step forward -- especially as physicians become more accustomed to accepting data from mobile sensors.
    neo-techtwokatmewPetrolDaveiHy
  • Reply 3 of 17
    I would love it. I. Would have bought it for me and for my parents and grandparents as well. 


  • Reply 4 of 17
    In general, the measurement doesn't require another device (though it requires user interaction then): Apple Watch is able to measure ECG and pulse. ECG measures electrical signal that allows to observe a moment of blood ejection from the heart (it's electrical, so fast travelling), while the pulse sensor registers the arrival of blood at the wrist. The only problem is that it requires the user to touch the watch with the other hand to close the electrical loop, so cannot be used in background. 
    twokatmew
  • Reply 5 of 17
    MplsPMplsP Posts: 3,271member
    There exist such devices currently but they are notoriously fickle. The method proposed here is interesting, as pointed out, it would need an additional electrode as well as a sensor tight enough on the wrist to sense the pressure wave. This alone would keep most from using it but then it wold be susceptible to changes in sensor location and need some sort of calibration. I'm not holding my breath!
  • Reply 6 of 17
    Do we really have data on many common measures, such as blood pressure, temperature, heart rate, O2, etc.? 

    Non- invasive measures on millions of people would be informative. 

    PetrolDave
  • Reply 7 of 17
    DAalsethDAalseth Posts: 1,733member
    I'm sure it will be out in 2021 because we just got AW6s and aren't looking to upgrade for some years. 
    JapheyGeorgeBMac
  • Reply 8 of 17
    Not with the low battery life they have.
    pulseimages
  • Reply 9 of 17
    All these features are going to zap that little battery. 
    Japheydavgreg
  • Reply 10 of 17
    JapheyJaphey Posts: 855member
    All these features are going to zap that little battery. 
    Yeah, but imagine the battery life we could have if they pulled it off while making it optional. I’ll bet they’re experimenting with kinetic energy to make it happen. 
    edited November 2020
  • Reply 11 of 17
    GeorgeBMacGeorgeBMac Posts: 10,298member
    larryjw said:
    Do we really have data on many common measures, such as blood pressure, temperature, heart rate, O2, etc.? 

    Non- invasive measures on millions of people would be informative. 


    Yeh, we do....  But, for Blood Pressure the standards keep changing.   Originally they didn't worry till it got well over 140/90.  Then 140/90 became the mark for prescribing BP meds.  Then the target became 120/80.   Then it was raised to 150/90 for older people.   But now many dispute that.

    The driver seems to be medication.  Once meds were available the target was lowered.   But raising it for older people was an attempt to balance the risks of hypertension against the risks of falling.

    But, evidence shows that populations who live healthy lifestyles (such as in rural Africa) don't need medication because their pressure stays at or below 110/70 throughout their life.
  • Reply 12 of 17
    All these features are going to zap that little battery. 

    I keep waiting for them to switch to detecting the electrical signal from the heart and scrapping the power hungry light.  The electrical signal is there and I've never figured out why they need a complete circuit (using a finger of the other hand) to complete it -- but obviously that's still necessary.   But, if they can figure it out, it would be both more accurate (It's the gold standard) and lower battery drain.
  • Reply 13 of 17
    I'm wondering whether Apple would get it approved by local authorities as a health device like they did with their ECG feature or if they will go the way of their SpO2% sensor and just call it a non-medical device.
  • Reply 14 of 17
    zimmiezimmie Posts: 554member
    All these features are going to zap that little battery. 

    I keep waiting for them to switch to detecting the electrical signal from the heart and scrapping the power hungry light.  The electrical signal is there and I've never figured out why they need a complete circuit (using a finger of the other hand) to complete it -- but obviously that's still necessary.   But, if they can figure it out, it would be both more accurate (It's the gold standard) and lower battery drain.
    Detecting voltage differentials on the order of tens of microvolts is extremely difficult with a floating ground. It might be possible if the watch's radios were the only ones within 5 meters or so, but how often is that the case? I put my phone on a charger near my bed. My Internet drop is in a closet attached to my bedroom, and that involves some electrically noisy equipment. If I sleep with a partner, that person's phone and/or watch would also probably be nearby. Maybe I have some alarm sensors on the bedroom window (lots of alarm companies are pushing wireless systems now), or maybe some "smart" lights to help wake me up in the morning. My watch doesn't even necessarily talk the same protocols as some of these devices, let alone have a trusted relationship which might let it tell them to quiet down for a second.

    So while yes, the electrical sensor could provide heart rate information under ideal circumstances, I think it would not work in the real world. Especially for Apple's market, which is likely to have more gadgets on average.
  • Reply 15 of 17
    Could the voltage differential be more easily detected if the watch strap itself had a sensor in it (on the opposite side of the wrist)?
    GeorgeBMac
  • Reply 16 of 17
    zimmiezimmie Posts: 554member
    Could the voltage differential be more easily detected if the watch strap itself had a sensor in it (on the opposite side of the wrist)?
    Not really. Like the sand said, we’re ugly bags of mostly water. The differential between two spots on the same extremity is minimal (since our blood is pretty conductive), and is more likely to be caused by local sources like the muscles in your forearm. ECGs work because the differential between your left and right arm can get up to about 1.2mV. Yes, millivolts. That’s about the max differential we see without invasive probes.

    It’s a reliable signal when you can hear it, but it’s extremely quiet. As a result, it’s very easy to drown it out. Reading from both arms helps reject noise.
  • Reply 17 of 17
    Looks like you have to wear an Apple Watch and an Apple Ring for this to work. Samsung currently has a watch on the market that can measure blood pressure from a single device (although the press release is somewhat vague).
    GeorgeBMac
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