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Posted By: rudied Proper accuracy testing of nibp - 17/06/21 12:28 PM
Hi. What is the best method to test for accuracy of dynamic pressures in nibp bpm found at doctor surgeries? If it had static measurement capabilities, that would be easy. I get too much variance in results if using a unisim vital signs simulator. Please help
Posted By: Geoff Hannis Re: Proper accuracy testing of nibp - 17/06/21 6:22 PM
There are so many variables that you haven't mentioned:-

1) Are the devices all of the same type (manufacturer and model)?
2) How many have you tested?
3) Are results reproducible?
4) Are cuff sizes all the same (and in good condition)?
5) Are the hoses all the same (condition, length)?
6) Are you concerned about pressure or BPM (or both)?
7) What sort of % variance are you experiencing?

Depending on which algorithms are used by various manufacturers, you may never get accurate dynamic results; but regardless of the tester being used, after testing a lot of NIBP units (of whatever type), and if you keep records, after some time you you will get a feel for when one or another results are outside "expected norms".
Posted By: Adrian Jones Re: Proper accuracy testing of nibp - 01/07/21 10:20 AM
We have a Fluke ProSim4 Vital Signs Simulator that we use for such devices but generally we know how to get in to the engineering / verification mode.

Where a user has managed to purchase a device we cannot find information on we use the simulator and keep records on that particular monitor and refer back to them.

Depending on the algotithm the manufacturer uses you should get consistent results using a simulator such as the Fluke.
Posted By: John Sandham Re: Proper accuracy testing of nibp - 21/07/21 1:05 PM
Its been qite a while since I put an NIBP machine on test, but I always considered a mercy sphyg the most accurate comparison for pressure.

The NIBP test devices from companies like Ultramedic and Rigel should be more than sufficient for doing planned maintenance inspections. (So long as they are calibrated)

If you are doing research - then a mercury column (mmHg) would my 'go to'.
After all - that is the measurement (mmHg) you are trying to check.
Posted By: Geoff Hannis Re: Proper accuracy testing of nibp - 21/07/21 5:27 PM
Happy days, John, happy days.

In my view, there's nothing wrong with reverting to First Principles ... in fact I would encourage all biomeds to think in that way ("adopting the mind-set", you might say).

After all, how accurate does this ward-based "vital signs" kit need to be, anyway?

See also electronic thermometers (expensive) - versus - mercury thermometers (accurate, and cheap).

Not so sure about Pulse Oximeters, though (unless my own finger is deemed good enough).
Posted By: Philip Page Re: Proper accuracy testing of nibp - 26/07/21 7:45 AM
G'day all.

Like you have mentioned above a mercury column sphygmo' will tell you if the unit under tests pressure transducer and associated measuring circuitry is working correctly - BUT for a vital signs monitor to measure this you need to put (most) vital signs monitor into a 'non patient mode' to test against a mercury sphygmo'.
Over here in the antipodes our legislation requires that we test the units in normal mode (i.e. How the unit is used on the patient). So dynamic simulators are important.
After measuring 100's (if not 1000's) of different units of many different manufacturers, I have noted that most (same model) will be within 1 or 2 mmHg BUT this can be different from another make/model unit.
I aim to catalogue these differences to see whats what.
P.S. Temperature and atmospheric pressure also come into play.

Posted By: Geoff Hannis Re: Proper accuracy testing of nibp - 26/07/21 3:52 PM
Does that legislation prohibit you from teeing off into a mercury column (sphyg)?

If you needed to get really technical, you could use a digital precision pressure meter (Druck, et al) with a data logger.

And 2 mmHg is well within acceptable limits for "monitoring", I would have thought.

I would be interested in seeing your data ... also your thoughts on how much temperature and atmospheric pressure affect NIBP testing results. My guess would be "negligible" - especially as I can't imagine either varying that much in any hospital setting.
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