The BHS Blood Pressure Measurement Working Party is responsible for maintaining an impartial list of validated blood pressure monitors on its website. The list is updated regularly with changes to the existing information and new devices.
The BHS now runs its own Validation Service for manufacturers of blood pressure monitors and successfully validated devices by the BHS are automatically added to the list of validated BP monitors on our website.
However, for successful validation studies performed on devices by other agencies, the procedure for inclusion in the BHS list of validated blood pressure monitors, is as follows:
An independent validation should be undertaken and passed using at least one of the following testing standards:
The full report of the validation study, describing the process and results should be published in a peer-reviewed journal. The Working Party is not obliged to suggest journals in which the validation paper should be published nor by whom the validation should be undertaken but this should be independent of the manufacturer.
The manufacturer may submit an electronic copy of the full published paper (abstracts will not be accepted) to email@example.com for review by the Working Party prior to any decision on listing being made. There is no charge for this service and members of the Working Party provide their services voluntarily. Therefore, a time-schedule for a decision cannot be given.
Validated devices will be added to the BHS website list under the most appropriate category heading. Where monitors have been only tested in a specific area, such as pregnancy, this will be clearly stated on the website.
The BHS logo cannot be used on devices tested by independent agencies.
To download the application form click here
What determines the accuracy of the blood pressure measurement device?
Implications for device equivalence
Figure: Simplified block diagram of an Automated non-invasive blood pressure measuring device
The accuracy of the device depends on the cuff; the transducer that records the cuff pressure and the amplifier and signal processing (e.g. some form of filter) that records the cuff pressure; the digitisation and subsequent digital signal processing that extract the oscillometric pulses; interpolation between sampled pulses and the algorithm used to analyse the oscillometric pulses and their variation with cuff pressure. The rate of change of cuff pressure during the measurement phase will affect measurement accuracy (traditionally during linear cuff deflation, but step deflation and measurement during inflation are also used). The inflation of the cuff (assuming measurement during cuff deflation) can also affect accuracy, for example dependent on the difference between the pressure that the cuff is inflated to and the systolic pressure.
Thus in declaring equivalence, manufacturers should state, with reference to the block diagram, if there are any changes in any of the numbered functional blocks
1. Cuff characteristics
2. Transducer, amplifier and any signal processing carried out prior to digitisation
3. Cuff inflation.
4. Cuff deflation.
5. Digitisation (sampling frequency and number of bits), and digital signal processing
6. Interpolation. The oscillometric pulses occur only every heart beat and it is not uncommon for designers to interpolate between pulses to increase the accuracy and reduce the measurement variability whilst increasing the cuff deflation rate (or inflation rate for those devices that measure during cuff inflation) to reduce the measurement time.