Evaluation of performance of selected devices for measuring blood pressure

Standardization of blood pressure measurements is critical for the implementation of screening programs, and especially so for a multicenter, collaborative investigation of community blood pressure control. This need arises from numerous well known sources of variability in blood pressure measurements, some of which are attributable to performance characteristics of instruments and observers. A number of instruments have been developed in recent years with the aim of overcoming certain aspects of this measurement variation. Consequently, the Coordinating Center of the National Heart and Lung Institute Hypertension Detection and Follow-up Program (HDFP) undertook to evaluate several of these devices in order to permit selection for this Program of optimal methods of blood pressure measurement. The mercury sphygmomanometer, which is the basis of most available epidemiologic data on blood pressure, was taken as the standard. In the first experiment, based upon a Graeco-Latin square design, none of the five automated devices tested compared favorably with the standard mercury sphygmomanometer, as judged by the mean values of multiple readings for each of the two specimens of each device. In a series of paired readings, all but one of the automated devices showed marked deviation from readings by the standard mercury sphygmomanometer. Qualitative observations on machine performance were also recorded and indicated serious operating difficulties with several devices-including, unfortunately, the device that had performed well in the second experiment. For the purposes of the Program, none of the automated devices tested performed adequately to recommend their substitution for the standard mercury sphygmomanometer. A modified type of mercury sphygmomanometer, designed to reduce observer bias, was included in this evaluation, did compare well, and will be used by the Program in conjunction with the standard device.