Hypertension, a condition affecting more than 50 million Americans yearly, is most commonly diagnosed by the measurement of blood pressure by cuff occlusion of arterial flow. This technique, which is more than 100 years old, requires careful attention to appropriate cuff size for accurate determination of blood pressure. In particular, using a cuff that is inappropriately small for the subject's arm will result in a false elevation of systolic and diastolic blood pressure. Obesity is increasing in prevalence in the United States and around the world. Increasing body weight is associated with an increase in arm circumference. Therefore the increasing prevalence of obesity accentuates the importance of recognizing the relationship between arm circumference and blood pressure cuff size and its impact on accurate blood pressure measurement. This is especially true with the increased use of out-of-office blood pressure measurement devices by the lay public for self-measurement or devices installed in public places. If out-of-office blood pressure devices are sold with an inappropriately small cuff which falsely overestimate blood pressure then important errors such as the over-diagnosis or excessive treatment of hypertension will likely occur. This study is the largest to address the issue of the distribution of blood pressure cuff sizes necessary accurately to measure blood pressure in a referral hypertension practice.
The study population consisted of 430 consecutive hypertensive patients who were seen by a single consultant (JWG) in the Division of Hypertension, Mayo Clinic Rochester over a period of 18 weeks in the fall of 1999. Hypertension was defined as in JNC VI; systolic blood pressure of 140 mmHg or greater, diastolic blood pressure of 90 mmHg or greater on more than one occasion, or taking antihypertensive medications. The study subjects represented a diverse hypertensive population. Patients included those with chronic stable hypertension coming to Mayo Clinic for a periodic evaluation as well as patients newly referred to the Division of Hypertension for evaluation of resistant or secondary forms of hypertension. The Mayo Clinic Rochester has a unique patients mix with more than 80% of patients from Minnesota and the neighboring states of North Central United States (North and South Dakota, Iowa, Wisconsin and Illinois), 15% from the other states and 2% international patients. Data collected on each patient included age, sex, weight, body mass index (BMI), sitting systolic and diastolic blood pressure using the appropriate size cuff. Arm circumference was measured at the mid-point of the right upper arm and recorded as less than 33 cm (standard arm cuff) or 33 cm or more (large adult cuff). Blood pressure was measured in the sitting and standing position with the arm supported at heart level after five minutes sitting in a quiet office. All measurements were carried out using a Baumanometer ® calibrated mercury sphygmomanometer and Baumanometer V-Lok ® standard arm and large adult cuffs by the author. Data were gathered in Microsoft Excel spreadsheet and statistical analysis carried out by the Department of Biostatistics of Mayo Medical School.
There were 430 patients in this study, 229 (53%) female and 201 (47%) male. The mean age (± SD) was 65.4 ± 13 years (R = 19–96), weight 84.5 ± 21 kg (R = 39.7–169.7), BMI 29.6 ± 6 (R = 15.9–38.8), systolic blood pressure 160 ± 25 mmHg (R = 100–252), and diastolic blood pressure 85 ± 13 mmHg (R = 56–126) (Table 1). Of these, 263 patients (61%), of whom 146 (56%) were males and 117 (44%) were females, had an upper arm circumference 33 cm or more and thus required a large arm cuff to measure blood pressure. Of the remaining 167 patients (39%) with an arm circumference less than 33 cm and used a standard arm cuff, 55 (33%) were males and 112 (67%) females.
Amongst all males 146 (73%) had an arm circumference of 33 cm or more and 55 (27%) less than 33 cm. Amongst all females 117 (51%) had an arm circumference of greater than or equal to 33 cm and 112 (49%) less than 33 cm. No patient in the study required a thigh cuff (arm circumference >47 cm).
There was a correlation between arm circumference of < 33 cm (standard arm cuff) and circumference of 33 cm or more (large adult cuff) and body size whether expressed as BMI (Fig. 1) or weight in kilograms (Figs. 2 and 3). In women an arm circumference of 33 cm or more was first seen at a weight of 60.2 kg and all women above 80.6 kg had an arm circumferences of 33 cm or more. In men an arm circumference of 33 cm or more occurred first at a weight of 76.6 kg and all men above 90.4 kg had arm circumferences of 33 cm or more.
The technique measurement of blood pressure by cuff occlusion, first promoted by Riva-Rocci, is more than 100 years old. JNC VI recommends that ‘the appropriate cuff size must be used to ensure accurate measurement. The bladder should encircle at least 80% of the arm. Many adults will require a large adult cuff’1. What has remained unclear is the prevalence of use of the different cuff sizes in an adult hypertensive population. This study is the largest in the world's literature and demonstrates that 61% of adults seen in a hypertension referral practice will have an arm circumference of greater than 33 cm and thus require a Baumanometer ® large adult cuff accurately to measure blood pressure. Several important observations are derived from this study.
In this study an upper arm circumference of greater than or equal to 33 cm was used to allow comparison of this population with that of Beavers 2. The company whose cuff was used in the study (Baumanometer V Lok cuff ® ) also identified 33 cm as at the lower end of the range as appropriate for the use of the ‘large adult’ cuff. Beaver et al 's 2 earlier prevalence study found that 15.7% of 209 hypertensives seen in a hospital hypertension clinic had arm circumferences of greater than 33 cm. In this multiethnic group the prevalence of arm circumference of greater than 33 cm ranged from 0% in Asian women to 46.9% in black women. It must be recognized that there were small numbers in each demographic group. No information about the other demographics such as body weight or age was provided. The difference in prevalence of large arm cuff size of 61% seen in this study and the prevalence of 15.7% seen by Beavers has several possible explanations. The first is that Beevers’ study looked at a more racially diverse population than in the current study. The Mayo Clinic patient population coming predominantly from the North-Central United States has an overrepresentation of patients of European heritage and under-representation of Asians, Hispanics and African-Americans. Differences in arm circumference based on race have not been reported except in the context of differences in ethnic prevalences of body mass.
Arm circumference and blood pressure cuff size usage is closely correlated with body size both as weight or BMI as this study shows. The rapidly increasing prevalence worldwide of obesity may explain the difference between this study and Beavers. Beevers’ observations were made in 1987 in an ethnically diverse population of 209 hypertensives seen in the Hypertension Clinic in Birmingham England. The worldwide prevalence of obesity has changed significantly in the last decade. In the USA the prevalence of obesity in adults has risen from 12% in 1991 to 17.9% in 1998. Sixty-three percent of men and 55% of women in the USA now have a BMI of 25 or greater meaning they are either overweight or obese 3. Not only is this the most likely reason for the current study's findings but it suggests that the use of large arm cuff will be increasing in the future as weight is correlated to arm circumference as seen in this study. Similar data for the increasing prevalence of obesity is reported from many countries where economic prosperity results in increasing food consumption 4,5.
The importance of the increased prevalence of large arm cuff usage relates to accurate blood pressure determination in the clinical management of hypertension. As others have previously shown, using too small a blood pressure cuff relative to arm circumference leads to a significant overestimation of blood pressure. Beginning at an arm circumference >29 cm 6, and with increasing inaccuracy as arm circumference increases 7,8 the standard cuff increasingly overestimates blood pressure. While using too large a cuff may underestimate blood pressure, its clinical impact on blood pressure management would appear to be less. Linfors et al. have shown that the errors in blood pressure measurement of using an inappropriately small cuff are far greater than that of using too large a cuff 9. In this study blood pressure was measured with a regular arm, large adult and thigh cuff in 470 patients, 350 patients with BMI less than 34 and 120 patients with BMI greater than 34. In the subjects with BMI less than 34, none of the cuffs misclassified the patient as having high blood pressure, borderline high blood pressure or normal blood pressure. In the subjects with BMI greater than 34, subjects were 2.2 times more like to be classified as hypertensive and 1.4 times more likely to be classified as borderline hypertensive when the standard arm cuff was used to measure blood pressure compared with when the classification was based on the more appropriately sized large adult or thigh cuff. A study by Manning et al. showed that the most frequent error in measuring blood pressure in an outpatient clinic was ‘miscuffing’, with undercuffing large arms accounting for 84% of the ‘miscuffings’10.
There are inflatable cuffs (Tricuff ® , Tricuff pressure group AB, Stockholm, Sweden) that are built with three different size bladders that can be adjusted for a wide range of arm circumferences. Despite studies showing it provides accurate blood pressure measurement beginning in 1990 11 this cuff has not become widely used in general practice. Finally if a patient has an arm circumference of greater than 33 cm and no large arm cuff is available, auscultation of the blood pressure can be accomplished in the forearm 12. By applying the standard adult blood pressure cuff over the forearm, holding it at the level of the heart, the blood pressure may be ausculted over the radial artery. These readings are not usually performed as falsely higher diastolic blood pressure readings may be obtained.
The message of the importance of using a cuff appropriately sized to the arm being used to measure blood pressure is particularly important when using out-of-office blood pressure measuring devices. Out-of-office blood pressure measurement is an increasingly common tool for managing hypertension. All blood pressure measuring devices currently available in the United States are sold with the standard adult cuff, the large adult cuff available as an option, often at higher cost than the standard adult cuff. This study shows that the majority of hypertensive patients using these devices would be at risk of overestimation of blood pressure using the standard arm cuff. This would place patients at risk of being incorrectly labeled as hypertensive and, if truly hypertensive, for over-medication of their hypertension. In addition many of these devices do not have the recommended arm circumference for the cuff enclosed labeled on the outside of the package. As shown in Table 2, each company differs in its definition of arm circumference appropriate to the phrase ‘standard adult’, ‘large adult’ etc. If the patient is to purchase an accurate out-of-office blood pressure measuring device, knowledge of both their own arm circumference and the recommended arm circumference for the device they are purchasing is critical.
This study has several weaknesses. First, the population is not demographically representative of the United States hypertensive population as a whole. Observations amongst Asian, Hispanic, and African-American hypertensives are needed to confirm the prevalence of the need for large arm cuffs. This study was designed to look at arm circumference as it related to blood pressure cuff usage in clinical practice, but individual arm circumferences were not recorded. A much larger, more diverse population than was seen in this study should be evaluated to represent more meaningfully the distribution of arm circumference in hypertensives and the population at large. Finally, this study did not attempt to look at the impact of bladder width and arm circumference, another important determinant of accurate measurement of blood pressure 13. In each patient in this study, the bladder width was felt by the investigator to be appropriate for accurate blood pressure measurement.
This study shows that 61% of adult hypertensives in a referral hypertension practice have an arm circumference of 33 cm or greater thus requiring a large arm cuff for accurate blood pressure measurement. The correlation of cuff size to body weight suggests that with the increasing prevalence worldwide of obesity, the use of large adult cuffs will increase not just in a referral practice but in the general population of hypertensives as well. There is an increasing interest in the use of out-of-office blood pressure measurement in the management of hypertension. All of these kits are currently sold with the standard arm cuff, the large cuff being offered as an option, often at an increased price. Education of the patient by the hypertension nurse or physician as to the appropriate sized cuff for the individual patient is necessary. Information to the patient on the outside of the package of out-of-office self-measurement blood pressure kits should advise the patient of the importance of choosing a blood pressure kit with a cuff size appropriate to the patient's own arm circumference. Alternatively, especially in the unsupervised discount store setting, the out-of-office blood pressure devices should be sold with the large adult cuff as the standard cuff. Both sizes should be readily available for purchase without an adverse price differential between the two cuffs as often exists now. Health care settings such as the emergency department or outpatient clinics where hypertensive patients are encountered should have easy access to both large adult and standard adult cuffs.
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