Measuring blood pressure accurately: new and persistent challenges.

Abstract

HIGH BLOOD PRESSURE IS A MAJOR PUBLIC HEALTH issue, affecting approximately 25% of US adults, or roughly 50 million Americans. The prevalence of high blood pressure increases dramatically with age, such that the lifetime risk of high blood pressure approaches 100%. Despite the availability of effective antihypertensive agents, rates of hypertension treatment and control have remained low and static over the last decade. Control of blood pressure begins with accurate measurement leading to appropriate diagnosis and treatment decisions. For more than 100 years, clinicians and researchers have used the mercury sphygmomanometer, a simple, gravitybased instrument, for blood pressure measurement. Because of its accuracy and reliability, the mercury sphygmomanometer is generally regarded as the gold standard against which all other devices for blood pressure measurement should be compared. In recent years, with the confluence of concern that mercury is contaminating the environment plus the development of electronic/digital equipment for blood pressure measurement, many health care institutions have replaced the mercury manometer with alternate equipment. Experience with the reliability of the mercury manometer has contributed to a lack of attention both to issues of accuracy and to regulation of nonmercury measurement devices. The effort to remove mercury manometers from health care facilities has created unanticipated problems and challenges to measuring blood pressure accurately. Recently the US Environmental Protection Agency (EPA) has identified mercury and mercury compounds as persistent bioaccumulative toxins. Most of the toxic effects of mercury are associated with mercury compounds, especially methyl mercury. Long-term exposure to mercury compounds has been associated with serious health problems, but the elemental mercury enclosed in manometers is quite stable and has rarely been reported to cause health problems. This same elemental mercury has been used in dental amalgam in fillings for years with no recognized toxicity. As part of EPA efforts, a memorandum of understanding regarding elimination of mercury waste was signed in 1998 between the EPA and the American Hospital Association. This memorandum created “Hospitals for a Healthy Environment,” a voluntary project requesting all hospitals to virtually eliminate mercury waste by 2005. The memorandum and the associated project have already led to mercury manometers being removed from many hospitals, health systems, and clinics. The controversy over mercury has led to an examination of several issues related to accurate blood pressure determination, involving both the instrument used and other issues of quality. These issues, recently discussed in a working meeting convened by the National Heart, Lung, and Blood Institute and the American Heart Association, should be of interest to clinicians, researchers, health care administrators, manufacturers, and policy makers.