Working Group on Blood Pressure Monitoring of the European Society of Hypertension International Protocol for validation of blood pressure measuring devices in adults

Abstract

Introduction With the increasing marketing of automated and semi–automated devices for the measurement of blood pressure, potential purchasers need to be able to satisfy themselves that such devices have been evaluated according to agreed criteria [1]. With this in mind, the Association for the Advancement of Medical Instrumentation (AAMI) published a standard for electronic or aneroid sphygmomanometers in 1987 [2] that included a protocol for evaluating the accuracy of devices, this being followed in 1990 by the protocol of the British Hypertension Society (BHS) [3]. Both of these were revised in 1993 [4,5]. These protocols, which differed in detail, had a common objective, namely the standardization of validation procedures to establish minimum standards of accuracy and performance, and to facilitate the comparison of one device with another [6]. Since their introduction, a large number of blood pressure measuring devices have been evaluated according to one or both protocols. Experience has, however, demonstrated that the conditions demanded by the protocols are extremely difficult to fulfil. This is especially so because of the large number of subjects who have to be recruited and the ranges of blood pressure required. The time required to complete a validation study is such that it is difficult to recruit trained staff for the duration of an investigation. These factors have made validation studies difficult to perform and very costly, with the result that fewer centers are prepared to undertake them. This is particularly unfortunate as more devices than ever before are in need of independent validation. When the BHS dissolved its Working Party on Blood Pressure Measurement, the Working Group on Blood Pressure Monitoring of the European Society of Hypertension (ESH) undertook to produce an updated protocol, which it has named the International Protocol. The ESH Working Group on Blood Pressure Monitoring is composed of experts in blood pressure measurement, many of whom have considerable experience in validating blood pressure measuring devices. In setting about its objective, the ESH Working Group recognized the urgent imperative to provide a simplified protocol that does not sacrifice the integrity of the earlier protocols. When the AAMI and BHS protocols [2–5] were published, the relevant committees did not have evidence from previous studies on which to base their recommendations. The ESH Working Group has had the advantage of being able to examine and analyze the data from 19 validation studies performed according to the AAMI and BHS protocols at the Blood Pressure Unit in Dublin [7–23]. A critical assessment of this database of evidence has permitted a rationalization and simplification of validation procedures without losing the merits of the much more complicated earlier protocols. The basic recommendations of the simplified International Protocol have been presented at meetings of the ESH Working Group, and the proceedings of these meetings have been published in order to invite comment and discussion [24–27]. The International Protocol has been drafted in such a way as to be applicable to the majority of blood pressure measuring devices on the market. The validation procedure is therefore confined to adults over the age of 30 years (as these will constitute the majority of subjects with hypertension), and does not make recommendations for special groups, such as children, pregnant women and the elderly, or for special circumstances, for example exercise. It is anticipated that the relative ease of performance of the International Protocol will encourage manufacturers to submit blood pressure measuring devices for validation in order to obtain the minimum approval necessary for a device to be used in clinical medicine, and that, in time, most devices on the market will be assessed according to the protocol for basic accuracy. It does not preclude manufacturers of devices from subjecting their products to more rigorous assessment and validation. Validation procedure Summary The validation team should consist of four persons experienced in blood pressure measurement: two observers and a supervisor (generally nurses), and an ‘expert’ (a doctor overseeing the entire procedure). If the doctor can be present throughout the entire validation procedure, he/she can take over the role of supervisor, thereby reducing the number of personnel to three. The validation procedure consists of the following steps Observer training and assessment. Two observers are trained in accurate blood pressure measurement. Familiarization session. The validation team becomes familiar with the workings of the device and the accompanying software. Validation measurements. Observer and device measurements are recorded on subjects in two phases. In the first phase, 15 subjects are recruited; devices passing this primary phase proceed to the secondary phase, for which a further 18 subjects are recruited. Analysis. An analysis of