How would you determine if a blood pressure cuff is sized appropriately for a patient?

J Clin Hypertens [Greenwich]. 2018 Jul; 20[7]: 1100–1103.

Abstract

The characteristics of the optimal cuff for blood pressure [BP] measurement are still the subject of much debate. The choice of the appropriate cuff in obese individuals depends not only on the arm circumference but also on its shape because a conically shaped arm makes it difficult to fit the cuff to the arm. When a large‐size cylindrical cuff is used in conical arms, an overestimation of the true BP is likely to occur with BP discrepancies that may be as large as 10 mm Hg. With the advent of automatic oscillometric devices, the choice of the appropriate cuff became even more controversial because with oscillometric BP measurement the reference point is not the artery occlusion but the oscillometric peak signal. To overcome the problem of miscuffing in obese individuals, special cuffs that can accommodate a wide range of arm sizes have been designed. Using these cuffs, accurate oscillometric BP measurements can be obtained over a wide range of arm circumferences using a unique software algorithm. These wide‐range cuffs coupled to oscillometric devices may represent a good option for BP measurement in very obese subjects. However, their reliability should be confirmed in larger populations and different settings.

Keywords: bladder, blood pressure, cuff, device, measurement, oscillometric

1. INTRODUCTION

In the past, doctors had only one way to evaluate blood pressure [BP] of a patient: the palpation of the radial artery and empirical judgment if the systolic pulse peak was strong or weak. Around the second half of 1800, the idea of applying an inflatable cuff with a mercury manometer allowed more reliable measurements. The current mercury sphygmomanometer method is still very similar to that proposed by Riva‐Rocci in 1896. However, the characteristics of the optimal cuff have been the subject of much debate since the beginning of the 20th century, and many problems remain debated.1, 2 With the advent of automatic oscillometric devices the choice of the appropriate cuff became even more controversial because the oscillometric measurement is generated by a different sequence of events compared to the auscultatory one. In fact, with traditional auscultatory technique, the role of the cuff is to compress the artery under a defined reference pressure, whereas with oscillometric devices, the cuff is at the same time the signal sensor.2 In the auscultatory BP measurement, a complete artery occlusion is necessary as a pre‐requisite for the systolic pressure determination. In the oscillometric method, the reference point is not the artery occlusion, but the oscillometric peak signal.3 Thus, the present recommendations for standard sphygmomanometry do not necessarily apply to BP measurement performed with oscillometric devices since the role of the cuff differs between the auscultatory and the oscillometric method.

2. THE CUFF AND BLADDER

With traditional sphygmomanometry, miscuffing may lead to inaccurate BP measurements, and the use of a cuff and/or a bladder of inappropriate dimensions for the arm circumference is a serious source of error. Use of too narrow or too short bladders [undercuffing] leads to overestimation of BP, and thus to overdiagnosis of hypertension, a problem overlooked by many doctors when measuring BP in obese subjects. Conversely, use of too wide or too long bladders [overcuffing] may lead to BP underestimation, with the possibility of diagnosing hypertensive individuals as being normotensive. However, there is still no consensus about the appropriate size of cuffs and bladders in relation to the upper arm circumference. The British Hypertension Society recommends a standard cuff with a bladder measuring 12 × 26 cm for the majority of adult arms, a large cuff with a bladder measuring 12 × 40 cm for obese arms, and a small cuff with a bladder measuring 12 × 18 cm for lean adult arms and children.4 Thus, the same cuff width is suggested for all types of arms. At variance, the recommendations of the American Heart Association are mainly based on the 40% × 80% rule.5 In other words, the bladder inside the cuff should have at least a 40% width and an 80% length of arm circumference. Thus, 4 different cuffs have been recommended to be used according to the arm size: a small adult cuff with a bladder measuring 10 × 24 cm for arm circumference 22‐26 cm, an adult cuff with a bladder measuring 13 × 30 cm for arm circumference 27‐34 cm, a large adult cuff with a bladder measuring 16 × 38 cm for arm circumference 35‐44 cm, and an adult thigh cuff with a bladder measuring 20 × 42 cm for arm circumference 45‐52 cm. However, an intraarterial study in which multiple indirect measurements were made with the cuff width/arm circumference ratio varying from 30% to 55% demonstrated that the problem is much more complex and that optimum cuff width for the indirect measurement of BP is proportional to the logarithm of the arm's circumference.6 A ratio of 40% resulted in an overestimation of BP for most arms, with particularly high errors for small arms. This overestimation indicates that the choice of the optimal cuff for BP measurement with the auscultatory method remains a clinical dilemma.

3. THE OSCILLOMETRIC BP MEASUREMENT

As stated above, current recommendations for cuff size may not apply to devices based on the oscillometric BP measurement. Indeed, little is known about the relationship between cuff size and performance for oscillometric monitors. This stresses the importance of the varying software‐cuff combinations in the different measurement methods. Complete artery occlusion is not critical when BP is measured with the oscillometric method because oscillations can also be detected beyond the systolic pressure through the knocking of the pulse at the overinflated bladder wall.2 Interesting results on the biomechanical basis of oscillometric BP were provided by Han et al using a computational model of the whole upper arm.7 This study showed that the measured cuff pressure oscillations are a reflection of the entire artery volume change under the cuff thereby presenting a mixture of arterial distension in different closure states during the entire measurement process. One advantage of the oscillometric over the auscultatory measurement was that although the oscillation amplitude was smaller with stiff than with elastic arteries the stiffness variation of the brachial artery did not affect the accuracy of oscillometric BP measurement.7

4. PROBLEMS WITH BP MEASUREMENT IN THE OBESE

As mentioned above, the regular adult cuff size is too short for individuals with an arm circumference of 32 cm or larger and will lead to overestimation of BP.8 Thus, obese subjects often require the use of large‐sized cuffs. According to the AHA recommendations, for arm circumferences ranging from 35 to 44 cm, a bladder measuring 16 cm in width should be used.5 For circumferences from 45 to 52 cm the bladder width should be 20 cm, but in subjects with short upper arm length, a 16 cm wide cuff can be used. However, a large arm often cannot be correctly cuffed especially in obese women with short humerus length. Results from our laboratory showed that arm length was