SUPPLEMENT 2: Progress in Hypertension Control || Errors in Assessment of Blood Pressure: Sphygmomanometers and Blood Pressure Cuffs

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  • Errors in Assessment of Blood Pressure: Sphygmomanometers and Blood Pressure CuffsAuthor(s): Norman R.C. Campbell, Donald. W. McKay, Arun Chockalingam and J. GeorgeFodorSource: Canadian Journal of Public Health / Revue Canadienne de Sante'e Publique, Vol. 85,SUPPLEMENT 2: Progress in Hypertension Control (SEPTEMBER / OCTOBER 1994), pp. S22-S25Published by: Canadian Public Health AssociationStable URL: http://www.jstor.org/stable/41991196 .Accessed: 14/06/2014 18:48

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  • Errors in Assessment of Blood

    Pressure: Sphygmomanometers and

    Blood Pressure Cuffs

    Norman R.C. Campbell, MD, FRCP(C),1 Donald. W. McKay, PhD,2 Arun Chockalingam, PhD,3 J. George Fodor, MD, FRCP(C), PhD3

    The equipment used to measure blood pressure is as critical as patient preparation and proper technique in obtaining accurate blood pressure readings.1"10 Many errors introduced by the sphygmomanometer and blood pressure cuff tend to be consistent and affect the readings of all patients each time blood pressure is evaluated with that equipment. A consistent error of 10 mm Hg could result in errors in the management of 40% of adult patients evaluated.6 With some types of sphygmomanometers, errors of this magnitude are not uncommon.5'10

    The most common sphygmomanome- ters used by physicians are the mercury and aneroid sphygmomanometers.6,7 Electronic devices are generally used by patients for home monitoring, but are occasionally used in physicians' offices.6,11,12 This article reviews the basis of current recommenda- tions for the maintenance of standard blood pressure measuring equipment.

    Blood Pressure Cuffs Assessment of blood pressure is the most

    common diagnostic procedure performed in the outpatient clinic.13 Most physicians have only a mid-sized adult cuff (12.5 cm

    1. Divisions of Internal Medicine and Geriatrics, Department of Medicine, Department of Pharmacology and Therapeutics, Faculty of Medicine, The University of Calgary, Calgary, Alberta, Canada.

    2. Division of Basic Medical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St John's, Newfoundland, Canada

    3. Division of Community Medicine, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, Canada

    Dr N. Campbell is supported by the Brenda Strafford Foundation. Author to whom all correspondence should be addressed: Dr D.W. McKay, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, Canada A1B 3V6. 709-737-6587.

    wide bladder) available for use in blood pressure measurement.6 Even the small percentage of physicians who own a variety of cuff sizes seldom use alternative sizes, despite the large range in arm circumfer- ence seen in their clinics.6

    Large cuffs are not only important for the measurement of blood pressure in obese patients, but when used within an acceptable range of arm circumference they are also recommended for routine use in the place of the common mid-sized cuff.1"4 An overestimate of diastolic blood pressure by 6 mm Hg occurs when a mid-sized cuff is used on a person ideally suited for a large-sized cuff, whereas use of a large cuff on an individual ideally suited for a mid- sized cuff causes an underestimate of 3 mm Hg.2 Table I indicates the error in diastolic blood pressure that occurs when blood pressure cuffs of different widths are used on arms of different circumferences. Since the use of a large cuff on a thin arm will underestimate blood pressure, it is neces- sary to have smaller cuff sizes available for younger patients and others with thin arms.2 Wide cuffs will also underestimate systolic blood pressure in thin patients.15 The Systolic Hypertension in the Elderly Program (SHEP) study, which demon- strated the benefit of treating isolated sys- tolic blood hypertension, used cuff sizes based on arm size.16 Therefore it may be best to use a cuff width selected to the patient rather than a single 'standard' cuff. The use of blood pressure cuffs with blad- ders that encircle the arm has been advo- cated in Britain17'18 and will also provide accurate results,19 but these cuffs are not widely available in Canada. Recently a cuff with a bladder that has variable expansion widths has been developed and may be beneficial if used properly.20

    S22 REVUE CANADIENNE DE SANT PUBLIQUE VOLUME 85, SUPPLMENT 2

    ABSTRACT

    This article reviews the current recom- mendations on equipment when blood pres- sure is measured by sphygmomanometer. The scientific rationale underlying the cur- rent recommendations for selection and maintenance of blood pressure measuring equipment is presented. The errors that can occur when the recommendations are not followed are quantified whenever the data are available. Inadequate assessment and mainte- nance of equipment often lead to the use of faulty equipment, and as a result errors in the assessment of patients' blood pressure are likely to be common. If followed, the current guidelines for use and maintenance of equip- ment would remove most of the problems noted. Physicians must ensure that properly maintained and appropriate equipment is used to measure blood pressure.

    ABRG

    Cet article passe en revue les recommanda- tions actuelles concernant le matriel quand la tension artrielle est mesure par un sphyg- momanomtre. Les raisons scientifiques la base des recommandations actuelles pour slectionner et entretenir l'quipement de mesure de la tension artrielle y sont prsen- tes. Lorsque les donnes sont disponibles, on y prcise l'importance des erreurs qui peu- vent survenir quand les recommandations ne sont pas suivies. Lorsque l'valuation et l'entretien de l'quipement ne sont pas adquats, on se sert d'quipement dfectueux, ce qui conduit des erreurs frquentes dans l'valuation de la tension artrielle des patients. Si l'on suit les direc- tives actuelles d'utilisation et d'entretien de l'quipement, la plupart des problmes cessent d'exister. Les mdecins doivent s'assurer que l'on se serve d'un quipement adquat et convenablement entretenu pour mesurer la pression sanguine.

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  • SPHYGMOMANOMETERS AND BLOOD PRESSURE CUFFS

    Many cuffs are marked by the manufac- turer to indicate the acceptable range of arm circumference. Unfortunately, these markings may not agree with the current recommended range and need to be checked and possibly remarked on each individual cuff.2 Marking the correct size range on the cuff helps with proper cuff selection and can be performed easily using a ruler and permanent marker.4 The ideal arm circumference for a cuff is 2.5 times the cuff s bladder width. Cuffs can be used on arms that have a circumference 4 cm of 'ideal'. When it is necessary to remark the cuff, start the measurement at the end that contains the bladder. Permanently mark the cuff at the ideal arm circumfer- ence, and then mark a line across the cuff at 4 cm on either side of the ideal circum- ference. The error introduced by using a cuff within the acceptable range is

  • SPHYGMOMANOMETERS AND BLOOD PRESSURE CUFFS

    Electronic devices are increasingly popu- lar with patients, but fortunately are rarely used by physicians.2'6'11 Like aneroid sphygmomanometers, these devices can lose accuracy,2'11'22 and routine' checks of calibration can be complicated by auto- matic inflation/deflation mechanisms.23 Accurate testing and calibration can be done by the manufacturer or by trained technicians. Furthermore, on equipment using microphones, placement relative to the brachial artery is critical. We and oth- ers have found the placement of micro- phones especially problematic when used on obese patients.11'20'22'24 Small changes in microphone placement over the brachial artery can produce substantial changes in pressure.9'19,22 In our experience, 6 to 8 mm Hg errors are common. We do not recom- mend these devices for routine office use.

    Ambulatory Blood Pressure Monitoring The noninvasive monitoring of blood

    pressure over 24 hours is becoming more popular.25 Ambulatory blood pressure mea- surements taken under routine daily living circumstances are reproducible and are a better reflection of some of the conse- quences of hypertension than a measure- ment at a single clinic visit.26"31 Furthermore, ambulatory measurements can be used in the prediction of cardiovas- cular morbidity.32 On average, the 24-hour diastolic blood pressure is 5 to 10 mm Hg below clinic measurement,26 and over 30% of patients classified as hypertensive on a single clinic visit will have normal 24-hour blood pressure readings.28 However, ambu- latory monitors can be annoying and uncomfortable for the patient and expen- sive, and erroneous data may be record- ed.24'33 These devices, if microphone- equipped, require meticulous placement and assessment of accuracy on every patient. Rarely, complications from nonin- vasive ambulatory monitoring can occur with trauma to neurovascular structures if the cuff fails to deflate or if it repeatedly inflates and the patient does not remove it.33 The devices are very useful, however, in delineating "white coat" hypertension, paroxysmal hyper- and hypotension, loss of diurnal variation of blood pressure, and the effectiveness of antihypertensive therapy over 24 hours.34 Ambulatory measurements

    can influence the decision to initiate anti- hypertensive therapy in certain patients.28,29,35 Although 24-hour blood pressure monitors have great promise for the future, they currendy share many of the accuracy and calibration problems of home electronic devices, and their role at present is still probably in the realm of the hyper- tension specialist or clinical investigator.

    CONCLUSIONS

    The use of defective and deficient equip- ment to assess blood pressure is common- place and likely leads to frequent and sig- nificant errors. Guidelines for the use and maintenance of sphygmomanometers have been established2 and if followed would resolve most of the problems noted. Care must be exercised in the use of new tech- nology for blood pressure measurement as many devices require maintenance and cal- ibration checks beyond the immediate resources of most physicians and patients. It is the responsibility of each physician assessing blood pressure to ensure that properly maintained and appropriate equipment is always used.

    ACKNOWLEDGEMENTS

    We thank Dr. P. Magner for reviewing this manuscript and Ms. Heather Arcari and Ms. Shirley Atkins for their expert sec- retarial assistance.

    REFERENCES 1. American Society of Hypertension.

    Recommendations for routine blood pressure measurement by indirect cuff syphygmomanome- try. Am J Hypertens 1992;5:207-9.

    2. Perloff D, Grim C, Flack J, et al. Human blood pressure determination by sphygmomanometry. Circulation 1993; 88:2460-70.

    3. Petrie JC, O'Brien ET, Littler WA, De Swiet M. Recommendations on blood pressure measure- ment. BMJ 1986; 293:611-15.

    4. Campbell NRC, Chockalingam A, Fodor JG, McKay DW. Accurate reproducible measure- ment of blood pressure. Can Med Assoc J 1990;143:19-24.

    5. O'Brien ET, O'Malley K. ABC of blood pressure measurement: The sphygmomanometer. BMJ 1979;2:851-3.

    6. McKay DW, Campbell NRC, Parab LS, et al. Clinical assessment of blood pressure. J Hum Hypertens 1990;4:639-45.

    7. Burke MJ, Towers HM, O'Malley K, et al. Sphygmomanometers in hospital and family practice: Problems and recommendations. BMJ 1982;285:469-71.

    8. Conceicao S, Ward WK, Kerr DNS. Defects in sphygmomanometers: An important source of error in blood pressure recording. BMJ 1976;1:886-8.

    9. Bowman CE. Blood pressure errors with aneroid sphygmomanometers (letter). Lancet 1981;1:1005.

    10. Perlman LV, Chiang BN, Keller J, Blackburn H. Accuracy of sphygmomanometers in hospital practice. Arch Intern Med 1970;125:1000-3.

    11. Canadian Coalition for High Blood Pressure Prevention and Control. Recommendations on self-measurement of blood pressure. Can Med Assoc J 1988;138:1093-6.

    12. Hunt JC, Frhlich ED, Moser M, et al. Devices used for self-measurement of blood pressure. Revised statement of the National High Blood Pressure Education Program. Arch Intern Med 1985;145:2231-4.

    13. National Center for Health Statistics, McLemore T. & Delozier J. 1985 Summary: National ambulatory medical care survey. Advance data from Vital and Health Statistics, No. 128. DHHS Pub. No. (PHS) 87-1250. Hyattsville, MD: Public Health Service, Jan. 23, 1987.

    14. Frhlich ED, Grim C, Labarthe DR, et al. Recommendations for human blood pressure determination by sphygmomanometers. Report of a special task force appointed by the Steering Committee, American Heart Association. Circulation 1988; 77: 502A-514A.

    15. Russell AE, Wing LMH, Smith SA, et al. Optimal size of cuff bladder for indirect measure- ment of arterial pressure in adults. J Hypertens 1989;7:607-13.

    16. Labarthe DR, Blaufox MD, Smith WM, et al. Systolic Hypertension in the Elderly Program (SHEP) Part 5. Baseline blood pressure and pulse rate measurements. Hypertension 1991;17:1162-1176.

    17. O'Brien ET, O Malley K. ABC of blood pressure measurement: Reconciling the controversies: A comment on "the literature". BMJ 1979;2:1201-2.

    18. O'Brien ET, O Malley K. ABC of blood pressure measurement: The sphygmomanometer. BMJ 1979;2:851-3.

    19. Van Montfrans GA, Van Der Hoeven GMA, Karemaker JM, et al. Accuracy of auscultatory blood pressure measurement with a long cuff. BMJ 1987;295:354-5.

    20. Stolt M, Sjonell G, Astrom H, Hansson L. The reli- ability of auscultatory measurement of arterial blood pressure. A comparison of the standard and a new methodology. Am J Hypertens 1990;3:697-703.

    21. Shaw A, Deehan C, Lenihan JMA. Sphygmomanometers: Errors due to blocked vents. BMJ 1979;1:789-90.

    22. Carroll KK, Latman NS. Evaluation of electronic, digital blood pressure monitors: Failure rates and accuracy. Medlnstrum 19...

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