Background

custo screen 400 (custo med, Ottobrunn, Germany) is a newly developed ABPM recording device for 24-hour blood pressure measurement. An important feature is the option to use it as a Holter ABPM recorder for synchronous recording of ABPM and Holter electrocardiograms (ECG). custo screen 300 is identical to custo screen 400, however without an ECG recording facility. Both systems are intended for use by trained specialist staff or physicians in clinics and offices. The measurement accuracy of both recorders is validated according to the currently most stringent requirements set by the European Society of Hypertension (ESH) – the criteria of ESH International Protocol (IP) 2010. [1]  Furthermore, the results were presented on the International Congress of Hypertension 2014, in Athens.[2]

Comparison of blood pressure measurements with blood pressure simulators

When checking the recorders with a BP simulator, the measured values occasionally deviate from the given initial systolic and diastolic values. This problem has been known in industry for a long time. As experience has shown, these deviations depend on the BP simulator used in each case. Although all BP simulators generate oscillation and fluctuation in order to simulate the haemodynamic conditions in the upper extremities, no simulator is actually capable of reproducing the entirety of physiological relations of a person’s upper extremities exactly. When comparing pressure line charts resulting from a measurement in a person with those generated by a simulator, significant differences can be observed (see appendix). Our own examinations with the BP simulators of the manufacturers “Fluke”, “Rigel”, “Dynatech Nevada” and “Gossen Metrawatt” (see ill. 1) occasionally show deviations from the initial values given in each case, fluctuating in the range of +2 to +5 mmHG with regard to systolic and +1 to +5 mmHG with regard to diastolic pressure.

[1] Source: http://www.dovepress.com/validation-of-the-custo-screen-400-ambulatory-blood-pressure-monitorin-peer-reviewed-article-VHRM.

[2] T. Mengden, A. Wolf, B. Beime, P. Bramlage (2014): The custo screen 400 is the first ambulatory measurement device to pass the European Society International Protocol 2010. Presentation on the Joint Meeting ESH-ISH of Hypertension (13.06.-16.06. 2014), Session 3, Late-Breakers. Athens, 16.06. 2014.

Illustration 1: Blood pressure simulators in use at custo med GmbH

Validation and measurement accuracy in a person

However, the decisive aspects for quality and thus for the reliability of the BP measurement are not the results from comparative measurements on simulators but the measurements performed in an exactly defined patient cohort.

This is the decisive reason why validation studies are always carried out with humans and never with blood pressure simulators. The requirements for conducting such studies are exactly defined in the criteria of ESH-IP 2010. For validation, this currently most stringent protocol stipulates that 33 subjects without arrhythmias and with clearly audible Korotkoff sounds are to be examined. The cohort of subjects comprises men and women representing different blood pressure types. Each subject goes through three test measurements with the BP device and immediately afterwards reference measurements are performed by experienced and trained observers. A detailed description of the method can be found in the publication of Bramlage et al. (2014).[1]  A summary of the results from the validation study can be viewed in the following table.

Table 1: Measurement results from the validation study custo screen 300/400

      (Source: Bramlage et al. 2014)

[1] See: Bramlage et al. (2014): Validation of the custo screen400 ambulatory blood pressure-monitoring device according to the European society of Hypertension international Protocol revision 2010. Vascular Health and Risk Management 10: 303-309.

The validation results show that from the 99 measurements performed in total, there were 100% within the 15% deviation limit, 99% within the 10% deviation limit and 85% within the 5% deviation limit.  Conversely, this means that 85% of all measurements carried out with the custo screen 300/400 recorders have a deviation of less than 5% from the actual measured value. Standard deviation for systole is 4.5 mmHG and for diastole 3.3 mmHG. As a consequence, the dispersion of values is extremely low and the measurement results are highly reliable and accurate. 

According to our knowledge, the recorders of series screen 300/400 belong to the ABPM recorders with the currently most accurate blood pressure reading worldwide.

If we exclusively trusted in recorders delivering most exact measurement results with blood pressure simulators, we could postulate that they will not provide any physiologically accurate measurement results in the actual patient cohort.  

Important note:

The contents made available here have been generated to the best of our knowledge and belief. We do not assume any responsibility for damages resulting from the use of the information contained herein. All liability claims are invalid. The readers are advised to check the accuracy of all product-related information.

Appendix

Comparison of a pressure line chart based on measurement in a person (A) with one created with a BP simulator (B)

A

B