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Evaluation of the Tensioday ambulatory blood pressure monitor according to the protocols of the British Hypertension Society and the Association for the Advancement of Medical Instrumentation Zso´ fia Ne´meth, Katalin Mo´cza´ r and Gyo¨rgy Dea´k Background The validation of ambulatory blood pressure monitoring devices is necessary to obtain information on their accuracy. The objective of the present study was to evaluate the accuracy of the Tensioday oscillometric ambulatory blood pressure monitor according to the protocols of the British Hypertension Society and the Association for the Advancement of Medical Instrumentation (AAMI). Design We followed the phases recommended by the British Hypertension Society protocol: before-use calibration, in-use assessment, after-use calibration, static device validation and report of the evaluation. However, we expanded on the protocol to accommodate features required by the AAMI. Method The accuracy of calibration of three Tensioday devices was tested before and after the in-use phase when each of three devices was performing 10 24 h sessions of ambulatory monitoring. As all three devices passed these phases, the accuracy of blood pressure measurement was tested in one arbitrarily selected device on 85 subjects for systolic and 85 for diastolic blood pressure values. This was done by comparing three sequential same-arm blood pressure readings obtained by the device with three readings obtained by two observers using standard mercury sphygmomanometer. The comparisons were carried out while resting in the seated, supine and standing positions for all subjects. The results were used to grade the performance of the device according to the British Hypertension Society protocol and to calculate the mean 7 standard deviation of the difference between the device and the observers, as required by the AAMI. Results The Tensioday device achieved an overall grade of A for both the systolic and diastolic measurements, and had a mean difference compared with the observer-measured blood pressure of 1.475.3/1.074.7 mmHg, which satisfies the AAMI criteria for accuracy. The British Hypertension Society grading did not change when patients with low, medium, and high blood pressure were analysed separately. The AAMI accuracy criteria were fulfilled in the standing and lying positions as well. Conclusion On the basis of these results, the Tensioday ambulatory blood pressure monitoring device can be recommended for clinical use for ambulatory monitoring. The accuracy of the device needs, however, further testing in special situations, such as in pregnancy, in elderly patients and during exercise. Blood Press Monit 7: 191–197 & 2002 Lippincott Williams & Wilkins. Blood Pressure Monitoring 2002, 7:191^197 Keywords: ambulatory blood pressure monitoring, validation, British Hypertension Society protocol, Association for the Advancement of Medical Instrumentation standard, hypertension 1st Department of Medicine, Faculty of Medicine, Semmelweis University, Budapest, Hungary. Conflicts of interest: None. Correspondence and requests for reprints to Dr Gyo¨rgy Dea´ k, Ph.D., 1st Department of Medicine, Faculty of Medicine, Semmelweis University, 2/a Koranyi u., Budapest, Hungary, H-1083. Tel: þ36 1 210 0278/1599; fax: þ36 1 313 0250; e-mail: deakgy@bel1.sote.hu. Received 29 August 2001 Revised 21 December 2001 Accepted 27 February 2001 Introduction Over the past decade, ambulatory blood pressure monitoring (ABPM) has become an integral part of the evaluation and follow-up of patients with hypertension [1]. Blood pressure values obtained using ABPM correlate better with hypertensive target-organ damage, and ABPM provides prognostic information over and above that provided by clinic measurements [2]. The use of ABPM in the evaluation of certain clinical situations, such as white-coat hypertension, drug-resistant hypertension, drug-induced hypotension, autonomic failure and treatment efficacy is endorsed by the Joint National Committee VI [3] and World Health Organization–International Society of Hypertension [4] guidelines for the evaluation and treatment of hypertension. The expansion in the use of ambulatory monitoring has led to the design and production of a variety of ABPM devices [5]. Manufacturers are not currently obliged to submit their devices for an independent validation of accuracy despite