Why Automated Office Blood Pressure Should Now Replace the Mercury Sphygmomanometer

The mercury sphygmomanometer is destined for obsolescence. Few medical devices have endured virtually unchanged for almost a century. Despite its use in many thousands of patients participating in clinical trials which established the benefits of drug therapy for hypertension, the mercury sphygmomanometer has now become an impediment to optimum care of the patient with hypertension in routine clinical practice. Manual blood pressure (BP) measurement is affected by a number of extraneous factors1–3 including those related to the patient (eg, anxiety), the health professional recording BP (poor BP measurement technique), and patient–health professional interaction (eg, conversation). The net result has been BP readings of variable quality and accuracy including a clinically significant white coat response in about 25% of patients, potentially leading to misdiagnosis or inappropriate drug therapy. Mercury is also now considered to be an environmental hazard and has been banned from the workplace in some European countries and from the wards of numerous hospitals in the United States and elsewhere.4 Automated oscillometric devices which have been validated for accuracy independent of the manufacturer are now available for 24-hour ambulatory BP monitoring (ABPM), home BP, and measurement of BP in the office setting. ABPM and home BP are now well established in clinical practice, have been shown to predict future cardiovascular events significantly better than manual BP, and have recently been advocated as replacements for manual BP in the management of hypertensive patients in the community.5–7 Notwithstanding the advantages of out-of-office BP, the use of repeated ABPM to manage the vast numbers of hypertensive patients is not feasible and not everyone is willing or able to record accurate home BP measurements. Even when home BP is performed properly, readings reported to the physician may be subject to “reporting bias” and may not always represent the actual BP values obtained by the patient.8 There is now an alternative to manual office BP measurement—automated office BP (AOBP). Automated oscillometric devices have recently been used in large-scale clinical trials9 and in population studies10 including the current National Health and Nutrition Education Survey.11 By incorporating validated, fully automated BP recorders into clinical practice, it is possible to improve the quality and accuracy of BP measurement in the office while eliminating most, if not all of the white coat response.12–14 AOBP involves the use of a fully automated, oscillometric sphygmomanometer to obtain multiple BP readings while the patient rests alone in a quiet room. Studies in community-based, primary care settings, in patients referred for 24-hour ABPM, and in patients referred to a hypertension specialist have all shown that AOBP can virtually eliminate the white coat response with AOBP readings being similar to the mean awake ambulatory BP.12,14 At present, there are at least 3 devices designed for professional use in the office or clinic setting on the market.15–17 If used properly, all 3 devices can produce more accurate readings and should be capable of eliminating the white coat response experienced by many hypertensive patients. AOBP has other advantages over manual BP measurement. Multiple readings can be taken without a health professional being present, thus saving valuable time of office personnel for other tasks. Unlike manual BP, AOBP readings are similar when taken in the office and in nontreatment settings such as an ABPM unit.18 Multiple AOBP readings can be taken as frequently as every 1 minute, from the start of one reading to the start of the next.19 Finally, the cutpoint for normal BP vs hypertension for AOBP (135/85 mm Hg) is similar to values for both awake ambulatory BP and home BP.12,14,20,21 A recent reevaluation of the cutpoint for a normal manual BP reading in routine practice has raised further questions about the use of the mercury sphygmomanometer.20 The traditional value of 140/90 mm Hg for defining hypertension was derived from carefully measured BP readings taken in the context of research studies or by specially trained health professionals in population surveys and in other similar research settings. However, manual BP measurement in routine office practice is usually not performed in accordance with recommended guidelines despite intensive efforts during recent decades on the part of organizations such as the American Heart Association to improve the quality of manual BP measurement in the community.22 In the “real world,” manual BP readings are of relatively poor quality and accuracy, often exhibit digit preference (rounding off to the nearest zero), have little or no correlation with target organ damage, and show a weak correlation with the awake ambulatory BP, a gold standard for determining future risk of cardiovascular events in relation to BP status.1,2,5–7 The net result is a “real world” cutpoint for manual BP/hypertension which is closer to 150/95 mm Hg instead of 140/90 mm Hg with about 25% of the patients exhibiting a clinically important white coat response, leading to possible overtreatment or inappropriate treatment of hypertension.23,24 Whereas, intensive education of physicians and other health professionals to improve the quality of BP measurement in routine practice has met with little success, the replacement of manual recorders such as the mercury sphygmomanometer with AOBP is relatively inexpensive, requires minimal training, and will make accurate BP measurement much less dependent on the expertise and training of the person recording the BP. Within the next year, additional studies using devices designed for AOBP will be reported, including national BP surveys in both Canada25 and the United States,11 a randomized, controlled trial of managing hypertensive patients with AOBP vs conventional, manual BP measurement in routine clinical practice,26 and clinical outcome data for AOBP in 14,000 individuals residing in the community.27 In Canada, about 10,000 BpTRU devices (BpTRU Medical Devices, Coquitlam, British Columbia, Canada) for AOBP are currently in use in clinical practice (M. Gelfer, personal communication) and the Canadian Hypertension Education Program will include AOBP as an option for routine BP measurement in the office in its annual guidelines update for 2010. An algorithm for the interpretation of AOBP has recently been proposed and validated in a population of untreated patients referred for 24-hour ABPM.21 The Canadian Hypertension Education Program is currently considering a revision of its algorithm for diagnosing hypertension using automated devices with 24-hour ABPM, home BP, and AOBP, all likely to appear as options for BP measurement in 2011. The key features of AOBP can be summarized by the acronym “AMA”: automated devices recording multiple readings with the patient alone in a quiet room. Using “AMA” principles, the adoption of AOBP into everyday practice in the community should lead to improved management of hypertensive patients.

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