[HN Gopher] Caltech Develops First Noninvasive Method to Continu...
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Caltech Develops First Noninvasive Method to Continually Measure
Blood Pressure
Author : crhulls
Score : 178 points
Date : 2024-08-10 03:53 UTC (19 hours ago)
(HTM) web link (www.caltech.edu)
(TXT) w3m dump (www.caltech.edu)
| dredmorbius wrote:
| This approach has been tried before. Bill Softky describes a
| startup he'd worked for using a similar sound-transduction
| continuous non-invasive blood-pressure monitoring technique. It
| ... had problems:
|
| _Our non-invasive device was supposed to measure blood pressure
| just as accurately [as an arterial line], but without the
| cutting, using specially-sculpted sonic vibrations and fancy
| algorithmic analysis, which was my job. The overall challenge was
| like measuring the pressure inside a bottle without opening it.
| Our device worked fine, in that our algorithmically-estimated
| blood pressure moved up and down, beat to beat, in lockstep with
| the actual blood pressure. The problem was that our estimate also
| moved up and down at other times as well, say when the patient
| moved her fingers, rotated her arm, or took vaso-constricting
| drugs like nicotine. I spent most of a year understanding these
| problems, and understanding they couldn't be solved before our
| funding ran out. That was when an old-timer taught me an
| important lesson of measurement: it's fairly easy to calculate a
| signal which correlates with what you want to measure, the way
| our vibration-estimate correlated with actual blood pressure.
| It's much harder, though, to calculate a signal which does NOT
| correlate with what you DON'T want to measure, like arm motion._
|
| <https://www.linkedin.com/pulse/monster-monetization-bill-sof...>
|
| I'd be _exceedingly_ curious as to how the CalTech team have
| solved that non-correlation problem.
| Timothy055 wrote:
| Looking at the diagram I'd suspect they use accelerometer
| information from both the wrist watch and the upper arm mounted
| sensor to remove the effects of arm motion. At simplest it
| could only check when the arm is in a neutral position. But I'd
| expect they did something more complex/better than that.
| dredmorbius wrote:
| As I understand Softky's work, it's not that the measurements
| varied _predictably_ with movements, it 's that they varied
| _unpredictably_.
|
| I'm obviously distant from the project, but a team of SWEs
| spending years trying to make nondeterministic data
| deterministic suggests a fairly deep problem.
| mhb wrote:
| Paper:
| https://academic.oup.com/pnasnexus/article/3/7/pgae252/77177...
|
| They tested on the carotid artery. I don't know whether they're
| concerned with addressing issues of wearing this while active.
| It seems more likely that it will be used in a clinical
| setting.
| phkahler wrote:
| The article mentions getting it down to an arm band or patch.
| Mistletoe wrote:
| It's just a blurb from a college PR team. As someone that came
| from academia, they don't have to have solved any of that
| because these are generally pretty worthless. It can be as
| small as someone in a lab discovered how to do the smallest
| thing and the college wants to run with it to look good.
| dredmorbius wrote:
| I'm aware. Which is why I'm pointing to someone who chased
| that "first" achievement for years, and has the scars to show
| for it.
| coldcode wrote:
| As a person who had a hypertensive crisis late last year, nothing
| boils my blood (yes, a pun, I am fine now) more than how people
| measure blood pressure incorrectly in doctors offices and even
| hospitals. There are many different things than can increase a BP
| measurement above the "baseline" including talking, moving
| around, not having rested but also just waking up, not being in a
| supported position, only a single value, etc. Most of the major
| health agencies (AMA,AHA,CDC, etc in the US) have recommendations
| on how to do it properly, but in medical situations like doctors
| offices and hospitals, these are rarely done as they take too
| much time. A single measurement is not sufficient and can result
| in misdiagnosis.
|
| A more reliable way to measure a continuum would make a
| difference, but I imagine it would still require time to collect
| as BP is a dynamic value that changes with behavior, posture and
| activity.
| nulbyte wrote:
| As an adult with a congenital heart defect and white coat
| hypertension, I can relate. Once, a nurse took my blood
| pressure and immediately freaked out as I was sitting calmly on
| the exam table. She took it again in the same arm, then
| hurriedly took it in each of my other limbs before throwing her
| hands up.
|
| Often, I would arrive at the cardiology office having made my
| way through downtown traffic to find a parking space and walk
| across the pedway. Then I'd find a seat as far away as possible
| from all the noisy children there to remind me that I should be
| dead. No wonder my BP is higher than usual. And you're the one
| freaking out?
|
| I got so used to nurses tossing out every recommendation for
| measuring BP that I started taking it myself at home before
| visits just to prove the point. Eventually, as I grew older, my
| BP rose to a point where it actually needed to be addressed. I
| am now on medication. But I have yet to find a nurse anywhere
| that has taken time to follow even one recommendation for
| properly taking BP.
| pkaye wrote:
| When I was a dialysis patient with frequent office visits,
| I've had the same experiences myself. Two things I've ended
| up doing is get to the hospital 30 minutes early, sit in a
| quiet area and relax till 10 minutes before the appt.
| Secondly I've found deep and slow breathing can improve your
| blood pressure a lot. The problem of white coat syndrome
| still remain though.
| dgacmu wrote:
| It's frustrating. I usually bike to the doctor's office, and
| every time I warn them that they're going to get a systolic 10
| higher than if they'll wait until the end of the appointment.
| They don't wait. The tech-taken entry gets put in the EMR. The
| doctor takes my BP again at the end, says "oh, great" and that
| reading gets ignored. :p
|
| As a sibling comment noted, I ended up deciding to just watch
| my BP at home every now and then. It turns out it's fine and it
| reduced my metaphorical blood pressure to monitor it myself.
| benmanns wrote:
| However, as discovered during a family heart crisis, medical
| professionals will routinely ignore any kind of heart rate or
| blood pressure readings that you take at home. In my
| experience, it's not until they see the same measurement
| during the ($$$) ambulance ride that they take it seriously.
| teamspirit wrote:
| I had hypertension for about 15 years and after quitting
| drinking and smoking no longer do. I still suffer from white
| cost hypertension regularly and frequently have to tell nurses
| to just press the button again - second time drops back to
| normal range with a drop of about 20/10.
| hn72774 wrote:
| I had it too. When I was under stress, sometimes I could hear
| my pulse in my ears like a whooshing sound.
|
| I stopped drinking and my BP is now completely normal, and
| RHR is low 40's. Sleep is much better too.
| temporallobe wrote:
| Are you serious? Your RHR is in the low 40s? Mine is
| typically 58-65 and I was told I have bradycardia!
| xattt wrote:
| > A single measurement is not sufficient and can result in
| misdiagnosis.
|
| During an acute care stay, a single blood pressure is a drop in
| the bucket. It averages out on the long term, and it's not
| taken out of context of a clinical presentation.
|
| I would take pressures manually, question unusual values,
| repeat on the spot and after some time had passed.
| blackeyeblitzar wrote:
| Totally agree and I think the malpractice comes from laziness
| and a lack of interest in their patients. If they cared, they
| would do it correctly per the guidelines they hand out to
| patients themselves! By which I mean these:
| https://www.heart.org/en/news/2020/05/22/how-to-accurately-m...
|
| It is especially bizarre to me when they don't listen to
| patients and make medical decisions like deciding prescriptions
| and dosage amounts based on false readings.
| ineedaj0b wrote:
| i don't think it matters too much. we don't want to take it
| right after you just exercised obviously, but even taking it
| once is indicative of things. 'i have white coat etc. i have
| nerves!' these are all things we don't mind seeing. all those
| those things connect.
|
| using up time to double check blood pressure is so/so useful
| but generally a waste. a patient's labs tell much more, and
| are better to hedge suspicions against.
|
| white coat hypertension at 320lbs!? alright sir we can check
| again if you like...
| HPsquared wrote:
| I find doctors and nurses rush things too much in general. I
| guess they're paid flat-rate, like mechanics?
| ineedaj0b wrote:
| there's just no time. we have to write down everything you
| tell us, we have to come off genial, make you sure you aren't
| lying about something or mistaken, and fix you.
| barbazoo wrote:
| They have a million patients. I bet no one on that moment
| thinks, oh I'm only paid $10.75 for this, I better rush this
| so I can earn more money.
| hereme888 wrote:
| I'm a resident physician and I deny having my BP taken in
| outpatient clinics.
|
| The techniques used are ridiculously inappropriate:
|
| "Ok, Mr. So-and-so, come with me." calls the nurse, as the pt
| who is irritated for having to wait 30 minutes quickly gets up
| to walk along unknown hallways, while rushing to finish a phone
| conversation, stressed and not knowing where to turn
| next..."Ok, now we're going to weigh you on this scale" while
| the pt thinks 'oh man, I've probably gained weight', followed
| by "ok, now we're going to measure your blood pressure." 'I
| don't want BP meds...let me try to relax...breathe
| slooowly...but I don't want the nurse to notice I may be trying
| to cheat this sudden examination.'
|
| That's why the most appropriate way nowadays is to measure it
| at home, and keep a BP log.
| thelittleone wrote:
| People try to cheat BP tests? Because they dont want tp taks
| BP meds? Daaaang I'm trying to get my head around that. I
| guess I'm missing something because that sounds like an
| incredibly tangled way to be.
| basementcat wrote:
| Pilots (and astronauts) lie to their doctors to avoid being
| grounded.
|
| https://www.washingtonpost.com/politics/2023/08/27/faa-
| pilot...
| slaymaker1907 wrote:
| One thing that I think would dramatically improve the routine
| screening numbers at doctors' offices would be to try and
| take it after the patient has been sitting down for a few
| minutes waiting for the doctor after the other vitals have
| been taken. If I'm going to sit around for 15m+ anyways, why
| not use some of that time to let BP stabilize?
| samstave wrote:
| This would be the best use of the "AI Pin" fiasco of a device;
|
| Create an AI pin that takes in all the activity associated with
| the BP monitoree, including telemtry for environment, movement,
| and diet. if I had a pin that did this (and recorded all audio
| for the day, and snapped pictures when I wanted and transcribed
| all audio via whisper and I had a full searchable day-runner...
|
| Yay!
|
| EDIT: The above desire is fully capable of a phone - except
| battery life...
|
| I have a boatload of old phones. It would be interesting to
| just build a mini-build for an android phone to simply be a
| daily recorder. to capture audio/video only and run a slow app
| that will transcribe all audio to text on the device (even if
| it does so once its on lan, then it connects to an endpoint
| running locally on your docker desktop fast api to capture the
| audio that auto uploads as soon as on home lan. Sorts the files
| and pics and everything onto the NAS with simple txAI workflow
| to ffmpeg as needed.
| jkid wrote:
| https://bodyport.com/ (YCS15). Not continuous, but is non
| invasive. Given the variability of blood pressure throughout the
| day...
| oezi wrote:
| This isn't measuring blood pressure, isn't it?
| barbazoo wrote:
| And it's not continuous either.
| ck2 wrote:
| No they didn't invent the first way
|
| The first way has been done in studies for years, maybe even a
| decade ago.
|
| Earlobes.
|
| I'll search for the papers later and link them.
|
| https://scholar.google.com/scholar?q=earlobe+blood+pressure
|
| https://www.todaysmedicaldevelopments.com/article/wearable-b...
|
| I've always wanted a Garmin linked ear-cuff device that uses the
| earlobe for heartrate and blood pressure and then doubles as
| music playback or alerts from the watch. You could even do body
| temperature from the earlobe reliably.
| queuebert wrote:
| This is quite an old problem. A quick search of PubMed yields
| 4834 results for "noninvasive blood pressure monitoring". Caltech
| has a weird definition of "first".
|
| Edit: To clarify, plenty of things have been tried besides the
| cuff, but most patients who need something more sophisticated
| than that are already sick enough to be in the ICU, where an
| a-line can be placed. This is really a solution in search of a
| problem.
| anon115 wrote:
| meowdoesnt the apple watch do this already? or was that just
| heart rate?
| rrrix1 wrote:
| Just heart rate and psuedo "EKG."
|
| BP monitoring requires a pressurized cuff which restricts
| (stops) arterial flow. The readings are the pressure of the
| cuff as it deflates when the blood starts flowing and when it
| can no longer be detected.
| Herodotus38 wrote:
| Aside from the home use, If this could be proven to be just as
| accurate as arterial lines this would be a huge benefit to
| patients in the ICU or undergoing major surgery where continuous
| blood pressure is needed. I hate putting in A-lines.
| _qua wrote:
| It's one of my favorite procedures! To each their own I guess.
| kekeblom wrote:
| Aktiia has a product on the market which supposedly already does
| this https://aktiia.com/uk/. It is based on an optical method
| though.
| trentnix wrote:
| A year or two ago, I interviewed a developer who worked for one
| of the companies trying to build these types of optical blood
| pressure sensors. I have high blood pressure so I was keen to
| learn more. The gist of his message was that even in excellent
| conditions, it was very inaccurate.
| benterix wrote:
| I wonder if things changed by now.
| robomartin wrote:
| I've been thinking a lot about continuos health parameter
| monitoring lately. For the last 100 days or so I have been
| running a personal health experiment and collecting multiple data
| points during the process. I guess some use the term "bio-
| hacking", not sure if it applies.
|
| The experiment has included multiple fasting periods, with a
| maximum of 7 days as well as changing one variable at a time in
| categories such as diet and exercise. The results have been very
| interesting and I intend to continue on this path until at least
| the end of the year.
|
| As part of the data collection I have been taking my blood
| pressure a minimum of twice a day, sometimes more. Also blood
| glucose, ketones and (consumer) EKG.
|
| The first thing that jumped at me was the inaccuracy or
| variability of these measurements. I even got a Dexcom continuous
| glucose monitor. Interesting but useless for my purposes. The
| thing produced 20% error with respect to finger poke
| measurements. And, then again, when I got a calibration kit to
| check my finger poke meter, the calibration range is
| approximately +/- 18%. In other words, unless you hit extremes it
| feels like these measurements are almost useless. You can kind of
| tell you are going up or down, yet don't really know where you
| are.
|
| The same, of course, has been true of blood pressure
| measurements. I went through three consumer machines. I can't say
| any of it is accurate because there are too many variables. I
| have run multiple experiments with regards to where and how to
| measure BP. All I can determine are relative changes by
| effectively measuring under as close to the same conditions as
| possible twice a day, morning and evening (both before meals).
|
| During the last month or so I have been using a protocol I
| learned from one of Andrew Huberman's presentations (can't
| remember which one or I would post a link). I believe he was
| interviewing a researcher who explained the process they use
| during their studies. In simple terms, they take three
| measurements and then average. The first is after 15 minutes
| sitting, feet on the ground, back supported, no movement, no
| speaking, no activity. The second and third are at 5 minute
| intervals under the same conditions. In other words, the entire
| process takes at least 25 minutes.
|
| After adopting this approach I have been seeing wildly different
| numbers with respect to the single measurement protocol I had
| been using for two months. In addition to that, the standard
| deviation of the computed values are much tighter now.
|
| This experience, so far, has made me wonder about just how many
| people might be misdiagnosed and put on medication every year
| because of bad data. I can see the value in having more data, of
| course. Yet, continuous data is only good if it is accurate to
| within a reasonable margin.
| ryukoposting wrote:
| Interesting. I recall working on some devices that implemented
| something called Pulse Arrival Time [1] which the biomeds on the
| team told me "isn't blood pressure, but it can be used for the
| same purposes."
|
| Does this technique have an advantage over PAT? How true is the
| statement that "PAT can be used for the same purposes?"
|
| [1]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6912522/
| pkaye wrote:
| This believe this blood pressure watch has been approved in a few
| European countries. It requires you to calibrate against the
| normal approach every month. I think they are trying to get it
| approved in the US by next year.
|
| https://aktiia.com/
| benterix wrote:
| I wonder how do you calibrate it in practice.
| hm-nah wrote:
| Huge deal for humans moving forward. ~5-8yrs too late for me
| (2-5yrs for product dev, 3yrs since a hemorrhagic stroke that was
| likely caused by serious blood pressure).
|
| I was 40 at the time and never measured my blood pressure (and
| certainly never when exercising). After the event I measured it
| all the time. During the 8th time of sitting in a chair, rolling
| up my sleeve, I thought, the Apple Watch has BP sensor, right?
|
| That question sent me on a quest only to find that humans had not
| yet figured out a way to measure blood pressure on-the-go.
|
| Congratulations on this effort!
| amelius wrote:
| > This measurement requires three parameters--a measurement of
| the artery's radius, the thickness of the artery's walls, and the
| tension or energy in the skin of the artery.
|
| Ok, so now instead of 1 variable, there are 3?
| ruckfool wrote:
| When will my apple watch support this ?
| bjornsing wrote:
| There's a company called Biobeat that sells a patch you put on
| your chest for continuous 24-hour blood pressure measurement [1].
| From what I've heard it's in clinical use and works.
|
| 1. https://www.bio-beat.com/cuffless-blood-pressure-monitoring
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