Heart Rate Under 40 BPM & Blood Pressure Monitors?

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Kieren Apr 2020 10:40am, 14 Apr 2020 3,906 posts	0 Kieren It seems all the blood pressure monitors from the big brands all use the same internal chipsets as they all seem to support readings from 40-180bpm. None of the customer service teams I reached out to are able to tell me if the product works for resting heart rates under 40BPM? (it's not clear if 40BPM was just chosen as a arbitrary number or if it is linked to to the sample rate, to gauge a reading) Do any Fetchies know? I assume a few of you have resting heart rates below 40BPM and might have a blood pressure monitor.
Carpathius Apr 2020 11:00am, 14 Apr 2020 19,303 posts	0 Carpathius I would imagine that BP monitors for sale to the general public wouldn't need to read below 40bpm. The majority of recreational athletes won't be below this, although high training distance runners might be and possibly sprinters (less sure about that, someone who knows will be about I'm sure). A rhr under 40 needs to be checked out by a doc.
Sam Jelfs Apr 2020 11:21am, 14 Apr 2020 612 posts	0 Sam Jelfs I wouldn't expect you to have a lot of luck getting a manufacturer to confirm if it will work under 40bpm or not, and mainly thats down to liability and the fact that it is outside of the range needed to be tested for certification. Chances are if the device sees a rhr less than 40bpm it will decide that the signal is erroneous, and refuse to give a reading. That said, I used to have a RHR less than 40bpm (it's crept up and sits around 45 these days), and used a Mobil-O-Graph for taking measurements, they are specced for 30 to 240 bpm, but they aren't cheap.
Daddy Shark Apr 2020 12:03pm, 14 Apr 2020 297 posts	0 Daddy Shark I've two things to say on this that might help: 1. I've been treated with high blood pressure for decades. The source was variously thought to be my weight (lost 3 stones but still high) or salt in diet (cut it, but still high). During most of that time I've been a regular runner and at my best I had a resting heart rate of 36 for a couple of years. I was continually using a cheap boots blood pressure monitor (form the approved list) and it always agreed with GP and hospital ones. One doc was worried about the 40 bpm issue and so compared it every time with the old fashioned "gold standard" way (using mercury column and Korotkoff sounds) and it always agreed. 2. In my work (Cognitive Neuroscientist using EEG) I sometimes have to consider the impact of low sampling rates on my measurements when dealing with low quality data. If cheaper monitors do have a low sampling rate this can impact their measurement of a peak and trough size (systolic and diastolic BP, the big and small numbers in your BP reading). The effect will be to, on average, underestimate the top number and overestimate the small number. You can mitigate this issue by repeating readings. The way my monitor works, it is clear that each time it measures it is not averaging several readings but just "listening" for the pressures that the korotcoff sounds start and end as it continuously deflates. This is good news. It means that repeated measurements will get you what you want, with the proviso that the tendency is to underestimate slightly the peak and overestimate the trough.
Kieren Apr 2020 12:08pm, 14 Apr 2020 3,907 posts	0 Kieren Thanks Sam, That is exactly why I am asking here. None of the manufacturers will comment but all seem bound by the specs of the chipset they use which I suspect is the same. The concern was that they wont work or give strange readings below 40 BPM. eL Bee did have an article on here years ago where runners had logged resting and max heart rate, so I know (although niche) there are lot of fetchies below 40BPM, so this seems the best place to get some niche wisdom. Mobil-O-Graph sounded good but on googling, seems to be about 20x what I would like to spend. I don't have a desperate need for a blood pressure monitor - sometimes I get a little light headed so would like something I can leave on my desk at work and take a reading to see if there is a correlation. Maybe I will just take a risk on one of the < £50 models from a vendor with a good return policy. ################ At my desk, resting heart rate is around the 35bpm mark after an easy day. A little less or more if it's been rest or strenuous. I'm not particularly fit - I think it just hovers around that value. In response to Carpathius, sound advice - in my case at least, the low HR is OK. It has been checked by cardiologists. 10 years ago it would often cause a concern but more recently front line (ie not heart specialists) seem to be more familiar with low heart rates. Nevertheless, I find it useful to keep some medical records accessible (on the cloud) so so I can show front liners what is normal for me
Kieren Apr 2020 12:13pm, 14 Apr 2020 3,908 posts	0 Kieren Daddy Shark - great answer. Thanks. The Boots one seems to be only £20 which is a bonus - small expense and even if it doesn't work for me my partner can get some use from it.
R4R Apr 2020 4:36pm, 19 Apr 2020 3,290 posts	0 R4R According to my Garmin 735, my RHR is 40 today, averaging 41 over the last 7 days (ranging from 37 to 45). Like you Kieren, I'm not particularly fit at the moment, with most of my exercise being walking the dog. I guess when I was running regularly it was nearer 35 on a regular basis. I DID have heart problems up to about 10 years ago, culminating in a PVI in 2012, and when I was in hospital, I was forever triggering the alarm on the heart monitor as my HR dipped below 40. In the end, they just disabled the alarm, to stop disturbing the other patients