Graham. has brought this to us :
On Thu, 21 Sep 2017 15:43:40 +0100, Harry Bloomfield
wrote:

I have the doctors panicking over my high blood pressure. So I dug out
a digi BP monitor we had for a few years #1. That had a problem with
its over pressure safety valve, which I repaired whilst waiting for a
new one to be delivered. It's readings were completely inconsistent, so
today (still waiting for #2 to arrive), I went out and bought an over
the counter #3.

#3 (a cuff auto digital) seems to provide consistent values, no rapid
wild variations, but how to be sure the displayed readings are correct?

I have already been advised that any of the larger pharmacists should
have a device to check the calibration of BP monitors, but I wonder if
there might be a way to check it at home?

I supply a service to pharmacies, or at least did so before I retired
earlier this year and I never saw such a calibration device or service
offered.

My late father was a medical rep in the 1960s and carried a little
bottle of Hg to top up doctors traditional sphigs, so I suppose that
was a calibration service.

Is your machine an upper arm cuff type? The wrist type are notoriously
inconsistent.

That might explain it. #1 is a wrist type, #2 when it arrives will be a
wrist type, #3 is a upper arm cuff type speced to be accurate to +/- 3
mmHg.