Hypertension is estimated to affect 43 to 56 million adults or 24% to 31% of the US

REVIEW ARTICLE Home Blood Pressure Monitoring Steven A. Yarows, MD; Stevo Julius, MD, ScD; Thomas G. Pickering, MD, DPhil Hypertension is estimated to affect 43 to 56 million adults or 24% to 31% of the US population and is emerging as a major health problem in some countries in the Third World. 1-3 Hypertension contributes to all the major atherosclerotic cardiovascular disease outcomes. Blood pressure (BP) can be monitored at the office (clinic) and at home using conventional or ambulatory BP monitors (ABPMs). Ownership of home BP (HBP) monitors is becoming popular and usually occurs without physician encouragement. 4 The world BP monitor sales have grown from $484 million in 1992 to $525 million in 1995 and are projected to grow to $597 million by 2002 (Eric Vennemeyer, written communication, December 10, 1997). Higher sales are likely due to the following factors: marketing and a population that is aging and increasingly obese and health conscious. These factors become more important as underdeveloped countries become similar to industrialized nations. 5 In the early 1980s, 7.5% to 17.0% of homes in the areas of Minneapolis St Paul, Minn, and Hamburg, Germany, had sphygmomanometers, whereas 44% to 66% of individuals with hypertension measured their own BP. 4,6,7 Of the patients recording the BP at home, 50% to 73% bought the monitor without physician advice and were not trained by qualified personnel. Despite the common use of these devices by patients, the only recommendation about the correct use of HBP monitors are from ad hoc panels of the American Society of Hypertension 8 and the Canadian Coalition for High Blood Pressure Prevention and Control. 9 Other groups encourage self-measurement of BP; however, From the Division of Hypertension, University of Michigan Health System, Ann Arbor (Drs Yarows and Julius); and the Department of Medicine, Cardiovascular Center, Cornell Medical Center, New York, NY (Dr Pickering). Dr Yarows has been and is currently a consultant to Omron Healthcare Inc, Vernon Hills, Ill. they are not specific on the use of the monitors for assessment of therapy. 10-14 The British Hypertension Society 15 did not mention HBP monitoring in their recommendations for management of essential hypertension. In this article, we review the history of HBP monitoring, types of monitors, how BP is determined, reliability and predictability of HBP monitors, and how HBP monitoring affects outcomes. HISTORY OF HBP MONITORING The first BP measuring device was developed by the Italian physician Scipione Riva-Rocci, MD, and brought to the United States by Harvey Cushing, MD, in 1901. 16 Brown 17 in 1930 was the first to report patient self-measurement of systolic BP for assessment of the effect of drugs. Ayman and Goldshine 18 were the first to report in 1940 that HBP was less than office BP (OBP). They suggested that HBP monitoring was useful for (1) instructing the patients about their chronic disease, (2) teaching physicians about the natural course of the disease and about factors that affect the disease, (3) learning the prognosis of the disease, and (4) increasing the precision of determining the effectiveness of treatment. TYPES OF AND DIFFERENCES IN MONITORS Several types of BP monitors are available for public use. The classic mercury manometer is not popular in the home and is becoming less popular for office use because of environmental concerns about 1251

Cuff Pressure 200 160 120 80 40 0 A s Korotkoff Sounds 157 108 A m A d Oscillations in Cuff Presure Oscillometric technique compared with the auscultatory technique for measurement of blood pressure (BP). A s indicates auscultatory systolic BP; A m, auscultatory mean BP; and A d, auscultatory diastolic BP. Reproduced with permission from Biomedical Instrumentation and Technology. 21 92 mercury leakage and waste. Aneroid manometers are used with a stethoscope and are usually inexpensive. However, they may be less accurate over time, leading to falsely low readings, and recalibration needs to be performed by the manufacturer. 19 Electronic devices may use an auscultatory or oscillometric method of detecting BP. The automated auscultatory method was first developed in the mid-1970s, and the oscillometric method was introduced in 1984. 20 The oscillometric method uses the small oscillations in cuff pressure to identify the systolic, mean, and diastolic pressures. 21 The mean BP is determined at the peak of the amplitude of the oscillations; the systolic BP, approximately 55% prior to the maximum; and the diastolic BP, approximately 85% after the maximum oscillations, although the exact points are proprietary to each manufacturer (Figure). Generally, there is a high correlation between auscultatory and oscillometric devices and simultaneous physician readings. 22 The auscultatory method tends to be influenced by unrelated noise, whereas movement influences the oscillometric method. Terminal digit preference, whereby the last numerical digit is rounded, was a more common feature with the stethoscope or aneroid technique (32.3%) compared with the automated electronic monitor (10.5%). 23 The oscillometric technique permits faster measurements and is cheaper to manufacture. 20 Oscillatory electronic devices have generally replaced auscultatory devices. Some electronic machines will inflate, deflate, and record the BP automatically, and others need manual inflation and deflation while the monitor records the BP. The selfinflating automated devices are especially useful for patients with arthritis. Some electronic devices have a printer attached and some will store readings that can be downloaded later. Some newer electronic machines use fuzzy logic, which anticipates the systolic BP to allow less overinflation and deflates in a linear as opposed to the usual stepwise fashion. The expense of the devices tends to be related to the degree of automation. Consumers generally prefer machines with digital readouts and are purchasing an increasing number of electronic HBP monitors (Eric Vennemeyer, written communication, December 10, 1997). 24 Sales of electronic monitors have increased from 57% of the world market in 1992 to 58% in 1995 and are expected to increase to 68% in 2002. US consumers purchased 44% of the world market of digital sphygmomanometers in 1992. Finger BP monitors are not accurate for home use. 25-28 Wrist measurement of BP using the oscillometric technique has been studied in more than 600 adults in 6 studies and in children and adolescents in 1 study (unpublished data from Omron Healthcare Inc, Vernon Hills, Ill). 29-34 There was generally good agreement compared with the upper arm measurement using auscultatory or oscillometric methods; however, the technique showed high variability in individual cases and the correlation coefficients generally were not as high as those using the upper arm method. The wrist measurements are very dependent on position of the device compared with the heart level. In the standing position with an upper arm cuff, BP is approximately 8 mm Hg higher with the arm positioned by the side rather than at heart level for both systolic and diastolic readings. 35,36 The formula for correcting the BP based on arm position is to subtract 2 mm Hg from the reading for every inch (2.54 cm) that the BP cuff is below the horizontal plane of the heart. 37 When the wrist manometers are used at the correct measurement level, the measurements are accurate. Stationary machines are often found in pharmacies for public use. The accuracy may vary considerably between machines. The Vita- Stat automatic, coin-operated BP measurement device (Spacelabs Medical Inc, Redmond, Wash) was found inaccurate for clinical use. 38-41 The accuracy of other devices that are currently used in community pharmacies has not been determined. These machines may increase the public perception about hypertension and may be considered only for initial self-screening for hypertension. IS HBP MONITORING ACCURATE? The common criticism of HBP monitoring is the uncertainty about whether the data are accurate. The reported accuracy of HBP monitors 1252

varies. The BP inaccuracy may stem from the operator of the device or from the device itself. There are many reasons within each of these categories, some of which are unique to the device (Table 1). Occasional differences of less than 5 mm Hg are rarely clinically important, especially if many measurements are taken. However, consistent differences of 5 mm Hg may result in the false diagnosis of new or uncontrolled hypertension. Unfortunately, the aneroid sphygmomanometers are similarly unreliable and were found to be inaccurate in 80% of the units tested at a university hospital and clinics. 42 The industry is regulated by the Food and Drug Administration in the United States, which uses the Association for the Advancement of Medical Instrumentation (AAMI) standards 43 for sphygmomanometers. Other countries use the standards of the British Hypertension Society 44,45 for BP measurement. The AAMI standards define passing as 95% or greater of the average measurements agreeing within ±10 mm Hg and 85% agreement within ±5 mm Hg. The device is expected to maintain the safety and performance characteristics for 10 000 full cycles. The pressure indicator accuracy is tested in the range of 20 to 250 mm Hg, and the monitor should not differ by more than ±3 mm Hg or 2% of the readings, whichever is greater. The British Hypertension Society standards assess differences between the test and standard sphygmomanometer by grading (eg, A for the most accurate and D for the least accurate) based on a summation of the percentage of readings with differences of ±5, ±10, and ±15 mm Hg. Before accuracy standards were developed, HBP monitoring was usually found to be inaccurate; however, some reports confirming accuracy were also found. 7,46-48 Once guidelines were published, reports assessed the compliance with the guidelines. Of 23 monitors, 12 (52%) met AAMI standards for diastolic accuracy (39% of devices met both systolic and diastolic standards), whereas 2 of 7 HBP monitors in another study 24 failed to meet AAMI criteria. Of the 7, 5 devices (71%) Table 1. Errors in Measurement All devices Incorrect placement of bladder, especially with ceramic microphone devices Incorrect bladder size (should be at least 80% and preferably 100% circumference of arm). An oversized cuff is accurate; however, an undersized cuff yields erroneously high readings 37 Inaccurate pressure gauge (except mercury) Measurement of Korotkoff IV sound Inadequate number of readings at 1 or several sittings Inaccurate recording of readings (intentional or otherwise) Leaking bulbs, valves, and hoses Aneroid devices Difficult number determination due to visual problems (especially nondigital) Inadequate stethoscope Stethoscope not over the brachial artery Terminal digital preference Inadequate hearing acuity Too rapid cuff deflation (especially with bradycardia or atrial fibrillation) Underinflation of cuff in combination with too rapid deflation leads to an error in systolic measurement Automatic devices Atrial fibrillation Transducer not over the brachial artery (auscultatory technique only) passed an interdevice variability assessment program (conducted by the British Hypertension Society 44,45 ) after 1 month of HBP monitor use twice a day. The following monitors were accurate and complied with the standards of the AAMI 43 and/or the British Hypertension Society 44,45 : Assure models A30 and W20 (Becton Dickinson & Co, Franklin Lakes, NJ); A& D models UA- 767 and UA-767PC (A & D Co, Ltd, Tokyo, Japan); Instromedix QD (ALARIS Medical Systems, Inc, San Diego, Calif); Omron models HEM- 706, 705CP, 711, 722c, 713c, and 403c (Omron Healthcare Inc); and Terumo model ES-H51 (Terumo Medical Corp, Somerset, NJ) (written communication, Osamu Shirasaki, September 2, 1998; written communication, S. P. Kerestan, July 1998; written communication, Jerry Wang, 1998). 23,49-54 ARE THE RESULTS OF ELECTRONIC HBP MONITORS REPRODUCIBLE AND WHAT ARE THE DIFFERENCES BETWEEN MONITORS? Home BP monitors have been shown to have reproducible readings, with an SD of less than 3.1 mm Hg for both systolic and diastolic measurements using an artificial oscillometric simulator that eliminates human variation. 55 When 2 different machines of the same model were also tested using this same simulator, differences of less than 3.6 mm Hg and SDs less than 0.7 mm Hg for both systolic and diastolic readings were seen. Thus, the results of the electronic machines are reproducible, and variation between machines of the same model is also clinically acceptable. HUMAN ERRORS IN BP MEASUREMENT Although OBP measurement has been the criterion standard, there have been errors with this method in nonresearch settings. The difference between the BP recorded using the correct technique and subsequent office measurements was 6 mm Hg for systolic and 10 mm Hg for diastolic BP. 56 Differences between a trained registered nurse and the usual health care providers were 6 mm Hg for systolic and 5 mm Hg for diastolic BP in a family practice center. 57 Potentially correctable errors that could be improved by training were estimated to be only 2 mm Hg for systolic and 1 mm Hg for diastolic BP. MEASUREMENTS OF HBP COMPARED WITH OBP AND ABPM The OBP is the criterion standard for determining hypertension-related cardiovascular morbidity and mor- 1253

Table 2. The Difference Between Blood Pressure (BP) Measured in the Office and at Home* Source, y No. of Patients Difference Between Office and Home BP,mmHg Systolic/Diastolic BP, SD Systolic Diastolic Home Office Sample Welin et al, 59 1982 31 6.1 0.6 15.4/11.5 23.6/14.1 Population-based study Kleinert et al, 65 1984 93 10.0 5.0 2/1 2/1 Hypertensive patients Bobrie et al, 66 1993 46 21.8 11.0 13.3/10.7 16.6/11.9 Hypertensive patients de Gaudemaris et al, 63 1994 390 8.1 4.8 8.0/8.5... Public health centers Sega et al, 60 1994 2400 8.0 7.0...... Population-based study Mancia et al, 61 1995 2400 8.6 7.4 17.0/10.0 16.8/9.8 Population-based study Sega et al, 62 1997 800 9.4 5.6 18.1/9.5 19.5/10.3 Population-based study Battig et al, 67 1989 101 8.6 4.0...... Normotensive and hypertensive patients Stergiou et al, 23 1997 Aneroid sphygmomanometer 46 4.4 4.9 12.2/9.9 14.3/9.3 Hypertensive patients with and Electronic sphygmomanometer 46 4.9 5.6 14.4/9.0 14.3/9.3 Hypertensive patients with and without treatment Average... 8.1 5.6......... *Ellipses indicate not available. Between difference of daytime office BP and home BP. Table 3. The Difference Between Daytime Blood Pressure (BP) Measured by an Ambulatory BP Monitor and at Home* Source, y No. of Patients Difference Between BP Measured by an Ambulatory BP Monitor and at Home, mm Hg Systolic/Diastolic BP, SD Correlation Coefficient Systolic Diastolic Home Ambulatory Systolic Diastolic Sample Staessen et al, 68 1991 328 4.0 5.0 22.0/16.0... 0.72 0.60 Population-based study Staessen et al, 69 1994 530 3.0 1.0............ Normotensive patients Stergiou et al, 23 1997 Aneroid sphygmomanometer 46 1.0 1.2 12.2/9.9 12.3/10.2 0.50 0.65 Hypertensive patients with or Electronic sphygmomanometer 46 0.5 1.9 14.4/9.0 12.3/10.2 0.59 0.72 Hypertensive patients with or Stergiou et al, 71 1996 50 4.2 0.3 15.0/10.2 13.5/11.2 0.56 0.68 Hypertensive patients with or Mancia et al, 61 1995 2400 3.8 4.0 17.0/10.0 11.0/7.9 0.79 0.65 Population-based study Sega et al, 62 1997 800 10.6 1.0 18.1/9.5 12.3/7.6...... Population-based study Bialy et al, 70 1988 32 2.3 0.5 11.8/7.1 11.7/8.4 0.82 0.48 Hypertensive patients Average... 1.7 1.2............... *Ellipses indicate not available. Between difference of daytime office BP and home BP. tality. It is therefore important to establish if HBP measurements are different than OBP measurements. Table 2 shows the summary of the difference between HBP and OBP. On average, OBP is 8.1/5.6 mm Hg higher than HBP. 58-66 Data from ABPM are often reported as 24-hour average and daytime average. The daytime average probably correlates better with the results from HBP monitors since patients usually obtain their BP during the daytime. Table 3 shows that the average difference between the results of daytime ABPM and HBP was 1.7/1.2 mm Hg, which is not clinically important. 23,59,60,64,67-70 NORMAL VALUES OF HBP AS DEFINED BY BOTH STATISTICAL ASSUMPTIONS AND MORBIDITY AND MORTALITY DATA There are 2 methods to define the limits of normality. 71 The first method is the distributional criterion, in which subjects whose BP exceeds 2 SDs of the mean are defined as hypertensive, and the second method relates BP to morbidity and mortality outcomes. Mejia et al 72 reported in 1990 the normal values for HBP based on a population-based study of 608 healthy adults aged 18 to 41 years. Using 2 SDs above the mean of the whole population as a cutoff point, the definition of hypertension for men was a BP of 142/92 mm Hg and for women, 131/85 mm Hg. This 1254

population was followed up for a mean of 3 years. 73 The authors sought an average HBP that would predict hypertensive BP in future office visits after 3 years with maximum sensitivity and at least 90% specificity. An HBP of 128/83 mm Hg or higher detected sustained hypertension with a sensitivity of 48% and a specificity of 93%. The PAMELA (Pressione Arteriose Monitorate E Loro Associazioni) study 59,60 was an Italian population-based study that followed up 2400 patients aged 25 to 64 years. The accepted upper limit of normal for OBP (140/90 mm Hg) using regression lines corresponded to an upper limit of normal of 120/77 mm Hg for both 24-hour average BP and HBP. The PAMELA project also followed up 400 elderly patients (aged 65 to 74 years). 61 Using the regression lines relating HBP to OBP, the upper limit of normal for HBP corresponding to an OBP of 140/90 mm Hg was calculated to be 133/82 mm Hg (95% confidence interval [CI], 131/80-135/83). A second population-based study 67 of 328 subjects determined that the 95th percentile for men aged 20 to 49 years was 150/93 mm Hg and for men aged 50 years and older, it was 157/90 mm Hg. The 95th percentile for women aged 20 to 49 years was 132/82 mm Hg and for women aged 50 years and older, it was 152/87 mm Hg. A third population-based study 62 determined that an OBP of 140/90 mm Hg corresponded to an HBP of 127/83 mm Hg. The normal HBP for men was 128/84 mm Hg and for women, 126/83 mm Hg. Home BP readings were obtained for 1913 population-based subjects who were followed up for a mean of 5 years in a rural Japanese community. 74 An excess of relative risk of 10% was arbitrarily accepted as a serious and substantial risk. Based on this assumption, the home reference value for defining hypertension was calculated to be 137/84 mm Hg or higher, which was equivalent to an excess risk associated with an OBP of 140/90 mm Hg or higher. The relative hazard (RH) of home systolic BP of 137 mm Hg or higher was 1.77 and of diastolic BP of 84 mm Hg or higher, 1.70. These investigators found that a U-shaped curve and a diastolic BP less than 65 mm Hg were associated with an increase of the RH to 1.54. Despite the differences in methods, the data across studies are reasonably consistent and suggest that the upper limit of normal HBP should be 130/80 to 135/85 mm Hg. This result is comparable to that reported in a meta-analysis 75 of 17 previous studies that suggested an upper limit of normal of 135/85 mm Hg. RELATIONSHIP OF HBP WITH END-ORGAN DAMAGE End-diastolic relative wall thickness was measured using M-mode echocardiograms in a comparative study of home, office, and 24-hour ambulatory BP monitoring. 64 The correlation coefficients were higher with home (r = 0.45/0.40; P.01) than office (r = 0.22/0.07) or 24- hour ambulatory BP (r = 0.26/ 0.24) readings. The effect of BP control on the evolution of electrocardiographic evidence of left ventricular hypertrophy was studied in 50 patients during an average 9-year followup. 76 The changes in electrocardiographic evidence of hypertrophy were related to the degree of BP control and correlated better with HBP average measurements rather than office measurements. IMPROVED PREDICTION OF HYPERTENSION-RELATED MORBIDITY AND MORTALITY WITH THE USE OF HBP MONITORING Home BP readings were obtained in a population-based study 74 for 1913 subjects whose mean age was 61 years who underwent a mean follow-up of 5 years in a rural Japanese community. The predictive power of HBP levels for subsequent mortality was slightly stronger than that of OBP. The RH for overall mortality for systolic HBP higher than 138 mm Hg was 2.06 (95% CI, 1.18-3.58; P.05), whereas for systolic OBP of 140 mm Hg or higher, the RH was 1.50 (95% CI, 1.05-2.15). The RH of diastolic HBP higher than 83 mm Hg was 1.90 (95% CI, 1.12-3.24; P.05), with a comparative RH for OBP higher than 90 mm Hg of 1.06 (95% CI, 0.62-1.79). COPING WITH HYPERTENSION USING HBP MONITORING Approximately 60% of the patients thought that HBP monitoring enabled them to cope better with the disease. 77 Physicians thought that patients who used HBP monitoring and had elevated BP values reacted on the whole reasonably, and the use of HBP monitoring allowed the patients to have a positive attitude toward their disease. 7 Of patients in one study, 78 96% thought that measuring their BP at home was worthwhile because of the reassurance that their BP was controlled. IMPROVED BP CONTROL USING HBP MONITORING The reports in the literature are mixed regarding improvement in BP control using HBP monitoring. Home BP monitoring was found not to lower BP after 6 months to 1 year of use in studies of patients with mild hypertension and patients with difficult to control hypertension. 79,80 Home BP monitoring was shown to lower BP in other studies (including one randomized, controlled trial) 78,81,82 with patients monitored for 6 months to 1 year. When patient self-directed adjustment of medication was combined with HBP monitoring, there was a significant decrease in mean BP measured by ABPM ( 0.95 mm Hg) after 8 weeks compared with the office-based, standard management group (+1.90 mm Hg; P =.04). 83 There is enough evidence of HBP monitoring improving BP control to justify a large randomized long-term study to clarify this issue. COMPLIANCE WITH THERAPY USING HBP MONITORING The reports in the literature are also mixed regarding the success of using HBP monitoring to improve compliance with therapy. Variations in study designs and definitions of compliance make it difficult to reach a definite conclusion; 1255

however, the general trend suggests a benefit. 78,83-87 COST-EFFECTIVENESS There are costs in measuring BP using office visits with or without the physician present. The yearly ambulatory care cost of hypertension treatment per patient at Veterans Affairs hypertension clinics was estimated as $647 in 1989 dollars. 88 Forty-nine percent of this cost was for clinic visits. We estimated that the total direct cost in Ann Arbor, Mich, for simply measuring BP in an office, without a physician present, is approximately $5.26. Patients also incur direct and indirect costs. In a study by Soghikan et al, 78 there were 1.2 (95% CI, 1.7 to 0.8) fewer physician visits over a year in a home-monitored group compared with the group that received usual care. The mean cost of hypertension care per patient in the homemonitored group was $117, which is 6% less than the group that received usual care. Although this difference was not significant (P =.44), out-of-pocket costs for transportation and lost wages were not calculated. CONCLUSIONS Home BP monitoring has become accurate since standards were developed. The results of monitoring are reproducible, with differences between models less than the differences due to human variation in the auscultation of BP. Home measurements result in lower BP readings than office measurements, with normal values similar to daytime ABPM. An OBP of 140/90 mm Hg is approximately equivalent to an HBP of 130/84 mm Hg. Although several studies indicate that HBP better predicts left ventricular hypertrophy and mortality than OBP, further research is needed. Additional studies are also warranted to determine if HBP monitoring improves BP control and compliance and is costeffective, although there have been studies showing benefits in each of these areas. It may be time to transfer HBP monitoring from a consumer market to a physicianendorsed activity, with appropriate third-party reimbursement for and physician review of the monitors. Accepted for publication September 9, 1999. Reprints: Steven A. Yarows, MD, Division of Hypertension, University of Michigan Health System, 128 Van Buren, Chelsea, MI 48118 (e-mail: syarows@umich.edu). REFERENCES 1. Burt VL, Whelton P, Roccella EJ, et al. Prevalence of hypertension in the US adult population: results from the Third National Health and Nutrition Examination Survey, 1988-1991. Hypertension. 1995;25:305-313. 2. Gupta R. Meta-analysis of prevalence of hypertension in India. Indian Heart J. 1997;49:450. 3. Ramirez MO, Pino CT, Furiasse LV, Lee AJ, Fowkes FG. Paraguayan National Blood Pressure Study: prevalence of hypertension in the general population. J Hum Hypertens. 1995;9:891-897. 4. Jeck T, Edmonds D, Mengden T, Schubert M, Vetter W. Performing self-measurement of blood pressure: a patient survey [in German]. Schweiz Rundsch Med Prax. 1991;80:456-461. 5. Frost & Sullivan information page. Profound Web site. Available at: http://www.profound.com/info /sources/researchline/f&s.html. Accessed February 23, 2000. 6. Hahn LP, Folsom AR, Sprafka JM, Prineas RJ. Prevalence and accuracy of home sphygmomanometers in an urban population. Am J Public Health. 1987;77:1459-1461. 7. Krecke HJ, Fleischmann C, Bokmann M. Distribution and acceptance of self-measurement of blood pressure in the Hamburg area [in German]. Schweiz Rundsch Med Prax. 1989;78:1336-1342. 8. Pickering T. Recommendations for the use of home (self) and ambulatory blood pressure monitoring. Am J Hypertens. 1995;9:1-11. 9. Campbell NR, Abbott D, Bass M, et al. Selfmeasurement of blood pressure: recommendations of the Canadian Coalition for High Blood Pressure Prevention and Control. Can J Cardiol. 1995; 11(suppl H):5H-17H. 10. The Sixth Report of the Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure. Arch Intern Med. 1997;157:2413-2446. 11. American College of Physicians. Automated ambulatory blood pressure and self-measured blood pressure monitoring devices: their role in the diagnosis and management of hypertension. Ann Intern Med. 1993;118:889-892. 12. 1986 Guidelines for the treatment of mild hypertension: memorandum from a WHO/ISH meeting. J Hypertens. 1986;4:383-386. 13. The 1988 Report of the Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure. Arch Intern Med. 1988;148:1023-1038. 14. The Fifth Report of the Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure. Arch Intern Med. 1993;153:154-183. 15. Sever P, Beevers G, Bulpitt C, et al. Management guidelines in essential hypertension: report of the second working party of the British Hypertension Society. BMJ. 1993;306:983-987. 16. Crenner CW. Introduction of the blood pressure cuff into U.S. medical practice: technology and skilled practice. Ann Intern Med. 1998;128:488-493. 17. Brown GE. Daily and monthly rhythm in the blood pressure of a man with hypertension: a threeyear study. Ann Intern Med. 1930;3:1177-1189. 18. Ayman D, Goldshine AD. Blood pressure determinations by patients with essential hypertension, I: the difference between clinic and home readings before treatment. Am J Med Sci. 1940; 200:465-474. 19. Petrie JC, O Brien ET, Littler WA, de Swiet M. Recommendations on blood pressure measurements. BMJ (Clin Res Ed). 1986;293:611-615. 20. Mieke S. Substitution of simulators for human subjects. Blood Press Monit. 1997;2:251-256. 21. Yong P, Geddes LA. A surrogate arm for evaluating the accuracy of instruments for indirect measurement of blood pressure. Biomed Instrum Technol. 1990;24:130-135. 22. Zachariah PK, Sheps SG, Smith RL. Role of selfmonitoring and ambulatory monitoring in diagnosis and evaluation of hypertension. Practical Cardiol. 1988;14:1-7. 23. Stergiou GS, Voutsa AV, Achimastos AD, Mountokalakis TD. Home self-monitoring of blood pressure: is fully automated oscillometric technique as good as conventional stethoscopic technique? Am J Hypertens. 1997;10(4, pt 1):428-433. 24. Evans CE, Haynes RB, Goldsmith CH, Hewson SA. Home blood pressure-measuring devices: a comparative study of accuracy. J Hypertens. 1989;7: 133-142. 25. Nesselroad JM, Flacco VA, Phillips KM, Kruse J. Accuracy of automated finger blood pressure devices. Fam Med. 1996;28:182-192. 26. Veerman DP, Lenders JW, Thien T, van Montfrans GA. LAM 100/Marshall F-88: accuracy and precision of a new device for discontinuous finger blood pressure measurement. J Hum Hypertens. 1993;7:113-115. 27. Teshima M, Kuwajima I, Inukai M, Suzuki Y, Matsusita S, Kuramoto K. Clinical evaluation of finger blood pressure measurement devices for home-use [in Japanese]. Nippon Ronen Igakkai Zasshi. 1993;30:54-58. 28. Iyriboz Y. Oscillometric finger blood pressure versus brachial auscultative blood pressure recording. J Fam Pract. 1990;31:376-380. 29. Weber F, Erbel R. Measuring blood pressure at the wrist: critical analysis of a validation study [in German]. Med Klin. 1995;90:562-566. 30. Bald M, Westhues R, Bonzel KE. Blood pressure monitoring at the wrist: is it reliable in children and adolescents? Z Kardiol. 1996;85(suppl 3): 106-108. 31. Thummler M, Wonka F, Schoppe A. Preliminary clinical comparative study of a new blood pressure instrument with wrist cuff [in German]. Z Kardiol. 1994;83:641-645. 32. Eckert S, Gleichmann S, Gleichmann U. Blood pressure self-measurement in upper arm and in wrist for treatment control of arterial hypertension compared to ABPM. Z Kardiol. 1996;85 (suppl 3):109-111. 33. Saul F, Klaus D, Aristidou Y, Wiemeyer A, Losse B. Non-invasive oscillometric wrist and upper arm blood pressure measurements compared with invasive values. Z Kardiol. 1996;85:127-129. 34. Latman NS, Latman A. Evaluation of instruments for noninvasive blood pressure monitoring of the wrist. Biomed Instrum Technol. 1997;31:63-68. 35. Mariotti G, Alii C, Avanzini F, et al. Arm position 1256

as a source of error in blood pressure measurement. Clin Cardiol. 1987;10:591-593. 36. Waal-Manning HJ, Paulin JM. Effects of arm position and support on blood pressure readings. J Clin Hypertens. 1987;3:624-630. 37. Ramsey M. Blood pressure monitoring: automated oscillometric devices. J Clin Monit. 1991; 7:56-67. 38. Polk BF, Rosner B, Feudo R, Vandenburgh M. An evaluation of the Vita-Stat automatic blood pressure measuring device. Hypertension. 1980;2: 221-227. 39. Whelton PK, Thompson SG, Barnes GR, Miall WE. Evaluation of the Vita-Stat automatic blood pressure recorder: a comparison with the Random- Zero sphygmomanometer. Am J Epidemiol. 1983; 117:46-54. 40. Salaita K, Whelton PK, Seidler AJ. A communitybased evaluation of the Vita-Stat automatic blood pressure recorder. Am J Hypertens. 1990;3(5, pt 1):366-372. 41. Whitcomb BL, Prochazka A, LoVerde M, Byyny RL. Failureofthecommunity-basedVita-Statautomated blood pressure device to accurately measure blood pressure. Arch Fam Med. 1995;4:419-424. 42. Bailey RH, Knaus VL, Bauer JH. Aneroid sphygmomanometers: an assessment of accuracy at a university hospital and clinics. Arch Intern Med. 1991;151:1409-1412. 43. Association for the Advancement of Medical Instrumentation. Electronic or Automated Sphygmomanometers. Arlington, Va: American National Standards Institute Inc; 1992:1-40. 44. O Brien E, Petrie J, Littler W, et al. The British Hypertension Society protocol for the evaluation of automated and semi-automated blood pressure measuring devices with special reference to ambulatory systems. J Hypertens. 1990;8:607-619. 45. O Brien E, Petrie J, Littler W, et al. Short report: an outline of the revised British Hypertension Society protocol for the evaluation of blood pressure measuring devices. J Hypertens. 1993;11: 677-679. 46. Weber F, Hirche H, Simonides R, Anlauf M. Comparative clinical study on the accuracy of conventional and electronic blood pressure selfmeasuring devices [in German]. Z Kardiol. 1981; 70:700-705. 47. Harrison DW, Kelly PL. Home health-care: accuracy, calibration, exhaust, and failure rate comparisons of digital blood pressure monitors. Med Instrum. 1987;21:323-328. 48. Imai Y, Abe K, Sasaki S, et al. Clinical evaluation of semiautomatic and automatic devices for home blood pressure measurement: comparison between cuff-oscillometric and microphone methods. J Hypertens. 1989;7:983-990. 49. James GD, Yee LS, Cates EM, Schlussel YR, Pecker MS, Pickering TG. A validation study of the Instromedix Baro-Graf QD home blood pressure monitor. Am J Hypertens. 1990;3:717-720. 50. Foster C, McKinlay S, Cruickshank JM, Coats AJS. Accuracy of the Omron HEM 706 portable monitor for home measurement of blood pressure. J Hum Hypertens. 1994;8:661-664. 51. Cordoba R, Fuertes MI, Alvarez A, Molina I, Solans R, Melero I. The evaluation of a self-measurement arterial pressure monitor: the OMRON-HM 722C [in Spanish]. Aten Primaria. 1997;20:247-250. 52. Mufunda J, Sparks B, Chifamba J, et al. Comparison of the Omron HEM-713C automated blood pressure monitor with a standard ausculatory method using a mercury manometer. Cent Afr J Med. 1996;42:230-232. 53. Walma EP, van Dooren C, van der Does E, Prins A, Mulder P, Hoes AW. Accuracy of an oscillometric automatic blood pressure device: the Omron HEM403C. J Hum Hypertens. 1995;9:169-174. 54. Kwek K, Chan Y, Tan KH, Yeo G. Validation of an oscillometric electronic sphygmomanometer in an obstetric population. Am J Hypertens. 1998;11: 978-982. 55. Yarows SA, Amerena JV. Accuracy of 10 models of home blood pressure monitors using a oscillometric simulator. Blood Press Monit. 1999;4: 45-52. 56. Rocha JC, Rocha AT, Magossi AMG, Leao RW, Palu MJF, Moreira DC. Evaluation of the technique for taking blood pressure by health care workers in an university hospital. Am J Hypertens. 1988;11:66A. Abstract. 57. Kay LE. Accuracy of blood pressure measurement in the family practice center. J Am Board Fam Pract. 1998;11:252-258. 58. Welin L, Svärdsudd K, Tibblin G. Home blood pressure measurements: feasibility and results compared to office measurements. Acta Med Scand. 1982;211:275-279. 59. Sega G, Cesana G, Valagussa F, Mancia G, Zanchetti A. Ambulatory and home blood pressure normality: the PAMELA study. J Cardiovasc Pharmacol. 1994;23(suppl 5):S12-S15. 60. Mancia G, Sega R, Bravi C, et al. Ambulatory blood pressure normality: results from the PAMELA study. J Hypertens. 1995;13(12, pt 1):1377-1390. 61. Sega R, Bravi C, Cesana G, Milesi C, Grassi G, Zanchetti A, Mancia G. Ambulatory and home blood pressure normality in the elderly: data from the PAMELA population. Hypertension. 1997;30(1, pt 1):1-6. 62. de Gaudemaris R, Chau NP, Mallion JM. Home blood pressure: variability, comparison with office readings and proposal for reference values. J Hypertens. 1994;12:831-838. 63. Appel LJ, Stason WB. Ambulatory blood pressure monitoring and blood pressure self-measurement in the diagnosis and management of hypertension. Ann Intern Med. 1993;118:867-882. 64. Kleinert HD, Harshfield GA, Picketing TG, et al. What is the value of home blood pressure measurement in patients with mild hypertension? Hypertension. 1984;6:574-578. 65. Bobrie G, Day M, Tugayé A, Chatellier G, Monad J. Self blood pressure measurement at home. Clin Exp Hypertens. 1993;15:1109-1119. 66. Battig B, Steiner A, Jeck T, Vetter W. Blood pressure self-measurement in normotensive and hypertensive patients. J Hypertens Suppl. 1989;7: S59-S63. 67. Staessen J, Bulpitt CJ, Fagard R, et al. Reference values for the ambulatory blood pressure and the blood pressure measured at home: a population study. J Hum Hypertens. 1991;5:355-361. 68. Staessen JA, Fagard R, Lijnen P, et al. Ambulatory blood pressure and blood pressure measured at home: progress report on a population study. J Cardiovasc Pharmacol. 1994;23(suppl 5): S5-S11. 69. Bialy GB, Ruddy MC, Malka ES, Silvay LA, Kamalakannan N. Comparison of office, home and 24- hour ambulatory blood pressures in borderline and mild hypertension. Angiology. 1988;39:752-760. 70. Stergiou GS, Malakos JS, Voutsa AV, Achimastos AD, Mountokalakis TD. Home monitoring of blood pressure: limited value in general practice. J Hum Hypertens. 1996;10:219-223. 71. Mejia A, Julius S. Practical utility of blood pressure readings obtained by self-determination. J Hypertens. 1989;7(suppl 3):S53-S57. 72. Mejia AD, Julius S, Jones KA, Schork NJ, Kneisley J. The Tecumseh Blood Pressure Study: normative data on blood pressure self-determination. Arch Intern Med. 1990;150:1209-1213. 73. Nesbitt SD, Amerena JV, Grant E, et al. Home blood pressure as a predictor of future blood pressure stability in borderline hypertension: the Tecumseh Study. Am J Hypertens. 1997;10:1270-1280. 74. Tsuji I, Imai Y, Nagai K, et al. Proposal of reference values for home blood pressure measurement: prognostic criteria based on a prospective observation of the general population in Ohasama, Japan. Am J Hypertens. 1997;10(4, pt 1):409-418. 75. Thijs L, Staessen JA, Celis H, et al. Reference values for self-recorded blood pressure: a metaanalysis of summary data. Arch Intern Med. 1998; 158:481-488. 76. Ibrahim MM, Tarazi RC, Dustan HP, Gifford RW Jr. Electrocardiogram in evaluation of resistance to antihypertensive therapy. Arch Intern Med. 1977; 137:1125-1129. 77. Krecke HJ, Lutkes P, Maiwald M, Schultze-Rupp A. Self-measurement of blood pressure in hypertensive subjects in Germany: results of a questionnaire in spring/early summer 1993 [in German]. Schweiz Rundsch Med Prax. 1994;83:895-900. 78. Soghikan K, Casper SM, Fireman BH, et al. Home blood pressure monitoring: effect on use of medical services and medical care costs. Med Care. 1992;30:855-865. 79. Johnson AL, Taylor DW, Sackett DL, Dunnett CW, Shimizu AG. Self-recording of blood pressure in the management of hypertension. CMAJ. 1978; 119:1034-1039. 80. Midanik LT, Resnick B, Hurley LB, Smith EJ, Mc- Carthy M. Home blood pressure monitoring for mild hypertensives. Public Health Rep. 1991;106: 85-89. 81. Stahl SM, Kelley CR, Neill PJ, Grim CE, Mamlin J. Effects of home blood pressure measurement on long-term control. Am J Public Health. 1984; 74:704-709. 82. Carnahan JE, Nugent CA. The effects of selfmonitoring by patients on the control of hypertension. Am J Med Sci. 1975;269:69-73. 83. Zarnke KB, Feagan BG, Mahon JL, Feldman RD. A randomized study comparing a patientdirected hypertension management strategy with usual office-based care. Am J Hypertens. 1997; 10:58-67. 84. Midanik LT, Resnick B, Hurley LB, Smith EJ, Mc- Carthy M. Home blood pressure monitoring in hypertension. Public Health Rep. 1991;106:85-89. 85. Edmonds D, Foerster E, Groth H, Greminger P, Siegenthaler W, Vetter W. Does self-measurement of blood pressure improve patient compliance in hypertension? J Hypertens Suppl. 1985; 3:S31-S34. 86. Haynes RB, Sackett DL, Gibson ES, et al. Improvement of medication compliance in uncontrolled hypertension. Lancet. 1976;1:1265-1268. 87. Nessman DG, Carnahan JE, Nugent CA. Increasing compliance: patient-operated hypertension groups. Arch Intern Med. 1980;140:1427-1430. 88. Stason WB, Shepard DS, Perry M, et al. Effectiveness and costs of Veterans Affairs hypertension clinics. Med Care. 1994;32:1197-1215. 1257