automated measurement of blood pressure in routine clinical practice

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In recent years, automated devices have been developed to record blood pressure (BP) accurate-ly in the home and during usual daily activities. Clinical outcome studies have clearly shown home BP and 24-hour ambulatory BP to be significant-ly better predictors of future cardiovascular events compared with BP recorded in the office setting using mercury sphygmomanometry. It is also now possible to measure office BP with the patient resting quietly alone in the examining room using an automated device. Studies in routine clinical practice using this approach have demonstrated that automated office BP can eliminate most of the white coat effect seen with manual BP mea-surement. The automated office BP also correlates significantly better than does the routine office BP with the 24-hour ambulatory BP, the gold standard for predicting risk of future cardiovas-cular events. Sufficient evidence now exists to consider incorporating automated office BP into an algorithm for diagnosing hypertension. (J Clin Hypertens. 2007;9:267–270) ©2007 Le Jacq

The measurement of blood pressure (BP) using mercury or aneroid devices continues to be

the standard of care for routine office practice despite recent advances in automated BP record-ers. Although guidelines for the management of hypertension such as the latest American Heart Association report1 mention home BP and 24-hour ambulatory BP monitoring (ABPM) as useful tools in evaluating a patient’s BP status, out-of-office readings have generally played a secondary role in the diagnosis of hypertension. Conventional measurement of BP in the office has not changed much in almost 100 years despite numerous studies showing that routine office BP correlates relatively poorly with target organ damage and is less predic-tive of clinical cardiovascular outcomes than either home BP or 24-hour ABPM.2,3

Numerous attempts have been made to reduce the white coat component of routine office BP measure-ments, including education of physicians and other health professionals on proper techniques for BP measurement, development of strategies to “relax” the patient, and methods for reducing patient-physi-cian interaction such as limiting conversation while readings are taken. Despite these attempts, routine measurement of BP in the office may not always reflect the patient’s true BP status.

The recent development of an automated device for measuring BP while the patient rests quietly alone in the examining room appears to be a major advance toward the goal of eliminating the white coat response in the office setting.

In a 1997 report, Myers and colleagues4 attempted to demonstrate lower BP values in the absence of an observer by comparing the mean of 2 readings taken by an automated Omron HEM-705 CP recorder (Omron Healthcare Co, Ltd, Kyoto, Japan) with the patient resting quietly alone in the examining room with routine readings taken using

R e v i e w P a p e r

Automated Measurement of Blood Pressure in Routine Clinical Practice

Martin G. Myers, MD, FRCPC;1 Marshall Godwin, MD, FCFP2

From the Schulich Heart Centre, Sunnybrook Health Sciences Centre and the Department of Medicine, University of Toronto, Ontario;1 and the Primary Healthcare Research Unit, Discipline of Family Medicine, Memorial University of Newfoundland, Newfoundland,2 CanadaAddress for correspondence: Martin G. Myers, MD, FRCPC, Sunnybrook Health Sciences Centre, A-202, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5 Email: [email protected] received January 3, 2007; revised February 2, 2007; accepted February 5, 2007

www.lejacq.com ID: 6512

The Journal of Clinical Hypertension® (ISSN 1524-6175) is published monthly by Le Jacq, a Blackwell Publishing imprint, located at Three Enterprise Drive, Suite 401, Shelton, CT 06484. Copyright ©2007 by Le Jacq. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the publishers. The opinions and ideas expressed in this publication are those of the authors and do not necessarily reflect those of the Editors or Publisher. For copies in excess of 25 or for commercial purposes, please contact Karen Hurwitch at [email protected] or 781-388-8470.

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a mercury sphygmomanometer by the patient’s own family doctor. Both the mean automated and manual office BP measurements were similar and each was significantly greater than the mean awake systolic BP. In retrospect, this study had 2 impor-tant limitations: (1) only 2 recordings were taken, and (2) the family doctors knew that they were taking readings as part of a research study, thus introducing the Hawthorne effect, which has been shown in previous studies to reduce the white coat response by improving the quality of the manual office BP measurements.5

Four years later, Gerin and associates6 reported significantly lower office BP values taken when patients were alone in the examining room using a nonvalidated automated device (automated Roche Arteriosonde 1216; Roche Medical Electronics, Cranbury, NJ). In this case, 15 readings were taken over 30 minutes, and manual readings were recorded using a Hawksley Random Zero sphygmomanometer (Hawksley, Lancing, Sussex, England). This study also had several limitations. As in the earlier study, readings were taken in the context of a research study that may have influ-enced the results. Also, the automated readings were taken over 30 minutes, a period known to result in decreasing BPs.7

A major advance in automated office BP measure-ment has been the development of the BpTRU (BPM 100/300) device (VSM MedTech, Ltd, Coquitlam, BC Canada). The BpTRU measures BP using the oscillometric technique and has passed independent validation studies.8 This device is designed to have the first measurement taken with the observer pres-ent in the examining room to make certain that the recorder is functioning properly with the cuff in the correct position. The first reading is then

discarded. The device then takes 5 additional read-ings at specific time intervals with the patient resting quietly alone in the examining room. It is possible to program the intervals from 1 to 5 minutes, but 2 minutes is generally used in clinical practice to avoid excessive discomfort of the upper arm with more frequent readings or excessively “basal” BP readings over a longer period. The price of the BpTRU unit is about $800. No additional costs should be necessary for taking a set of readings since BP measurement is part of the clinical examination. Nonetheless, some physicians may charge a fee for using the BpTRU device, at least until less expensive automated BP recorders become available for office use.

Recent studies have evaluated the BpTRU in routine clinical practice without requiring informed consent or involvement in a “research study” thus eliminating the Hawthorne effect. In the first study involving 22 patients,9 the mean (± SE) BP taken by the BpTRU (155±5/88±2 mm Hg) was significantly lower than the routine manual BP taken with a mercury sphygmomanometer on the first visit to a hypertension specialist (174±5/92±2 mm Hg) and also lower than the last routine reading taken by the patient’s own family physician (166±4/89±3 mm Hg). All readings were higher than the mean awake ambulatory BP (146±3/82±2 mm Hg).

In a subsequent study10 involving 50 consecutive hypertensive patients from a clinical practice referred to a hypertension specialist for further management, the mean (± SD) BpTRU value of 142±21/80±12 mm Hg was significantly lower than the manual BP taken by the hypertension specialist (163±23/86±12 mm Hg). The first automated reading (162±27/85±12 mm Hg) taken with the physician present in the examining room was similar to the manual BP. This study also demonstrated the time course of the BP decrease over 10 minutes (Figure 1), with the low-est “steady state” BP occurring between the fourth and sixth readings, thus confirming the need to take more than 2 or 3 readings.

Beckett and Godwin11 have compared readings taken on a single visit to the doctor’s office by a research assistant using the BpTRU device, with conventional readings taken by the patient’s own family physician during 3 visits before entry into the study. In a series of 481 hypertensive patients, the mean routine (1 reading on each of the 3 visits) office BP was 151±10/83±8 mm Hg, whereas the first BpTRU reading was 150±21/83±12 mm Hg and the mean of 5 readings taken over 10 minutes with patients alone was 140±18/80±10 mm Hg. The corresponding mean awake ambulatory BP (142±13/80±8 mm Hg) was similar to the mean

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- #1 #2 #3 #4 #5 #6 Automated (BpTRU) readings

85 81 80 80 79 79

162147 143 140 141 141

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Figure 1. Mean blood pressure values taken by the physi-cian (reading #1) using an automated recorder (BpTRU; VSM MedTech, Ltd, Coquitlam, BC, Canada) and 5 additional readings with patients resting quietly alone in the examining room. Adapted from Myers.10


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VOL. 9 NO. 4 APRIL 2007 THE JOURNAL OF CLINICAL HYPERTENSION 269

BpTRU value. The optimum cut point for a normal automated office BP (<135/85 mm Hg) was deter-mined by examining different levels of the office BP in relation to achievement of target awake ambula-tory BP (<135/85 mm Hg). Using the target mean awake ambulatory BP of <135/85 mm Hg, sensitiv-ity, specificity, positive predictive value, and nega-tive predictive value for the automated office read-ing at the cut point <135/85 mm Hg was 68/81%, 67/64%, 52/89%, and 80/48%, respectively.

A limitation of this study was the recording of the BpTRU readings by a research assistant and not by the patients’ own family doctors. In a previ-ous study,9 lower values were noted when auto-mated readings were taken by a research assistant, but, in this instance, BP recordings were performed outside of the routine office setting.

Beckett and Godwin also noted that the mean automated office BP value correlated significant-ly better with the mean awake ambulatory BP (r=0.571) compared with the routine office BP (r=0.145). Numerous studies have reported ambu-latory BP (awake, nighttime, and 24-hour) to be a better predictor of clinical cardiovascular outcomes than office BP.2 Thus, the automated office BP should provide a better indicator of cardiovascular risk than the conventional office BP, presumably by reducing the confounding effect of the white coat response generated by the presence of the observer in the examination room.

These studies provide support for the use of automated BP measurements in routine clinical practice, ideally with the patient being left alone in

the examining room while the actual readings are being taken. Although there is at least 1 other device marketed for this purpose, the Omron model 907, its main limitation is that it does not discard the first reading and takes only 2 or 3 readings in total. Data from studies with the BpTRU device9 would suggest that inclusion of all 3 initial readings would only partly reduce the white coat effect.

There are now more than a dozen clinical outcome studies demonstrating ABPM to be a significantly better predictor of clinical cardiovascular outcomes than office BP.2 Similar studies have reported home BP to be superior to office BP in predicting clinical outcomes.3 Both ABPM and home BP have now been recommended for routine use in the diagno-sis of hypertension by the Canadian Hypertension Education Program.12 Reduction of the white coat effect by both of these methods has undoubtedly been the primary factor in eliminating “dilution bias” and improving the predictive value of the automated BP measurement. There is little reason to doubt that the same will be true for the automated office BP, especially when these readings are highly correlated with ABPM. Most other guidelines committees have not as yet recommended ABPM or home BPs in the routine evaluation of hypertensive patients.

It should be noted that previous studies using automated office BP measurements have not spe-cifically presented data on untreated patients being evaluated for a diagnosis of hypertension. Most study populations included both treated and untreated patients when comparing automated office BP with mean awake ambulatory BP.

Manual BP recording

Normal BP High BP

Normotensive Automated BP recording

If masked hypertension suspectedNormal BP High BP

Confirm with ABPM or home BP White coat hypertension Diagnosis of hypertension

High BP Normal BP

Diagnosis of hypertension

Follow with (automated)

office BP

Figure 2. A suggested algorithm for diagnosing hypertension using automated blood pressure (BP) measurements (ABPM) in routine clinical practice.


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In a study that is currently underway, the Conventional versus Automated Measurement of Blood Pressure in the Office (CAMBO) trial, up to 1000 patients in 100 family practices in the com-munity will be followed for 2 years, half with routine office BP and the other half using the automated BpTRU device to manage patients. The primary out-come measure is the relationship between each of the office BP measurements and the ambulatory BP. The impact of the automated vs routine office BP on other aspects of the management of hypertension in these individuals will also be examined. The CAMBO study may confirm that the automated BP taken in routine office practice is a better predictor of car-diovascular risk than conventional BP measurement, with the automated device more closely approximat-ing ambulatory BP, the gold standard for the assess-ment of BP status and cardiovascular risk.

What is the current role of automated BP mea-surement in the office while we await further data from studies such as CAMBO? Based on currently available data, one might recommend using an automated device in routine clinical practice as an adjunct to the management of hypertensive patients (Figure 2). BP should initially be recorded with a conventional mercury or aneroid sphygmomanom-eter. If the reading is normal, then the patient should be considered normotensive (unless masked hyper-tension is suspected). If the conventional manual BP is high, the office readings should be repeated using an automated device such as described in this report. If the automated BP reading is also high, the patient likely has hypertension, which may be con-firmed with 24-hour ABPM (or home BP), if white coat hypertension is still suspected.

If the automated BP reading is normal, the patient should return on another day for a repeat automated BP reading. If the BP remains nor-mal, white coat hypertension may be diagnosed. If masked hypertension is suspected, a 24-hour ABPM or home BP can be performed to clarify the patient’s BP status. If the out-of-office BP is also normal, a diagnosis of white coat hypertension is confirmed and the patient can then be followed.

In other instances where home BP or ambula-tory BP data are not available, marked differences between the manual office BP and the automated BP reading should enable a physician to detect and quantitate white coat effect and avoid overtreat-ment of hypertension. At present, the use of the automated device falls into the category of individ-ual clinical judgment while further data on the use of automated BP in the office are being obtained. In the future, it is possible that automated office BP

will be used in the same way as home BP for the diagnosis of hypertension.

The limitations of the conventional measure-ment of BP in the office are well-known and have been carefully documented by numerous investiga-tors. Nonetheless, it is important to remember that manual BP measurements have been correlated with clinical outcomes in large, long-term, popula-tion studies and reductions in office BP in clinical trials have been associated with substantial reduc-tions in morbidity and mortality. Automated BP devices may, however, offer a means of obtaining a more clinically relevant measure of an individual patient’s BP status by reducing errors in the manual recording of BP and eliminating patient/observer interaction during BP recordings.

Disclosure: The CAMBO study is supported by a grant-in-aid from the Heart and Stroke Foundation of Ontario.

REFERENCES 1 Pickering TG, Hall JE, Appel LJ, et al. Recommendations

for blood pressure measurements in humans and experi-mental animals. Part 1: blood pressure measurement in humans: a statement for professionals from the sub-committee of Professional and Public Education of the American Heart Association Council on High Blood Pressure Research. Hypertension. 2005;45:142–161.

2 Myers MG. Ambulatory blood pressure monitoring for routine clinical practice. Hypertension. 2005;45:483–484.

3 Verberk WJ, Kroon AA, Kessels AG, et al. Home blood pressure measurement: a systematic review. J Am Coll Cardiol. 2005;46:743–751.

4 Myers MG, Meglis G, Polemidiotis G. The impact of physi-cian vs automated blood pressure readings on office-induced hypertension. J Hum Hypertens. 1997;11:491–493.

5 Myers MG, Oh PI, Reeves RA, et al. Prevalence of white coat effect in treated hypertensive patients in the commu-nity. Am J Hypertens. 1995;8:591–597.

6 Gerin W, Marion RM, Friedman R, et al. How should we measure blood pressure in the doctor’s office? Blood Press Monit. 2001;6:257–262.

7 Culleton BF, McKay DW, Campbell NR. Performance of the automated BpTRU measurement device in the assess-ment of white-coat hypertension and white-coat effect. Blood Press Monit. 2006;11:37–42.

8 Mattu GS, Perry TL Jr, Wright JM. Comparison of the oscillometric blood pressure monitor (BPM-100(Beta)) with the auscultatory mercury sphygmomanometer. Blood Press Monit. 2001;6:153–159.

9 Myers MG, Valdivieso MA. Use of an automated blood pres-sure recording device, the BpTRU, to reduce the “white coat effect” in routine practice. Am J Hypertens. 2003;16:494–497.

10 Myers MG. Automated blood pressure measurement in rou-tine clinical practice. Blood Press Monit. 2006;11:59–62.

11 Beckett L, Godwin M. The BpTRU automatic blood pressure monitor compared to 24 hour ambulatory blood pressure monitoring in the assessment of blood pressure in patients with hypertension. BMC Cardiovasc Disord. 2005;5:18.

12 Hemmelgarn BR, McAlister FA, Myers MG, et al, for the Canadian Hypertension Education Program. The 2005 Canadian Hypertension Education Program (CHEP) rec-ommendations for the management of hypertension. Part 1: blood pressure measurement, diagnosis and assessment of risk. Can J Cardiol. 2005;21:645–656.


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automated measurement of blood pressure in routine clinical practice

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