Thanks for that Grahame. Just one thing out of interest and further to your original comments:
Not so much as how it's taken, but which monitors actually do the job properly as opposed to claims of being A/A rated?
A lot of the monitors I've come across are fine on a simulator or perfect patient, but not so good in actual practice.
I assume you're not particularly interested in aneroid sphygmomanometers then, considering that the accuracy of the reading is down to technique (as long as the basic calibration meets specifications). Plus I've not seen simulators that dynamically (you did mention simulator?) test these (though I use leak-test and monometer function on our simulator to do static cal).
Possibly your interests lie with the semi-automatic types (that need to be manually inflated and initiated) and those automatic ones that are just dirt-cheap (that cycle at pre-determined intervals).
Just thought I'd mention that there is a BS standard for safety and essential performance of automatic cycling of NIBP monitors (where determinations are initiated automatically by the device); IEC 60601-2-30:2000. My approach would be to avoid any auto-cycling devices that don't purport to meet this standard in their literature. You get what you pay for really - just a thought.
This aside, I would have thought that the following standards are relevant and that manufacturers of medical equipment would be obliged to meet certain requirements of them. They might give some clues to testing anyhow.
BS 1060-1:1996 Specification for non-invasive sphygmomanometers. General requirements BS 1060-2:1996 Specification for non-invasive sphygmomanometers. Supplementary requirements for mechanical sphygmomanometers BS 1060-3:1997 Specification for non-invasive sphygmomanometers. Supplementary requirements for electro-mechanical blood pressure measuring systems BS 1060-4:2004 Specification for non-invasive sphygmomanometers. Test procedures to determine the overall system accuracy of automated non-invasive sphygmomanometers BS EN ISO 14155-1:2003 Clinical investigation of medical devices for human subjects. General requirements BS EN ISO 14155-2:2003 Clinical investigation of medical devices for human subjects. Clinical investigation plansIn order to make a truly objective comparison of the accuracy of any blood pressure measurement devices it's probably necessary to get right back to the clincal validation stage. Otherwise try motion artefact and arrythmia simulations using the NIBP similator to see which devices are most tolerant and give readings that are reproducible and that you're happy with.
Absolute accuracy of these devices is difficult because the dynamic measurement is affected by lots of factors i.e. it is less reproducible than the static accuracy measurement. Since clincal testing is done under reproduceable conditions on test-subjects I guess that "real-world" scenarios are not taken into account (but there are so many where do you start?). Accuracy os also relative to a "gold standard" method, correlation to IBP or simultaneous manual measurements by experienced practitioners.
Hence assessment of measurement accuracy becomes more of a statistical process just to obtain more reproducible figures or, if you don't wish to go down that route, quite subjective in the real world i.e. does one device produce results that "look better" than other devices using NIBP simulator "X" or are the users "happier" with the readings on real-world patients? I wonder if those cheap units have been clinically validated? I assume so.
