This article illustrates the importance of using the right size of the cuff to measure blood pressure and how the accuracy of readings differs if an improper size is used.

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Cross-sectional randomised trial cuff

This trial has given us robust new evidence that blood pressure (BP) measurement needs to be done with the right cuff. In the Cuff Size Blood Pressure Measurement study, 195 community members were given two to three sets of three BP measurements, 30 seconds apart, using automated and validated equipment with a BP cuff that was appropriately sized, one size lower, and one size higher. Randomisation was used to determine the order of cuff sizes.

1. Patients walked for two minutes before each set, followed by five minutes of rest, to remove the influence of prolonged rest intervals between tests on the outcomes.
2. Additionally, the room was kept silent, and participants were requested to refrain from speaking or using their smartphones. The mean age of the participants was 54 years, 34% were male, 68% were Black, and 36% had a body mass index of at least 30 kg/m2, satisfying the criteria for obesity.
3. Approximately half had a self-reported diagnosis of hypertension, 31% had a systolic blood pressure of 130 mm Hg or more, and 26% had a diastolic blood pressure of 80 mm Hg or greater.
4. Adult cuff sizes were determined by arm circumference (mean, 34 cm) and were as follows:
   • Small (20 - 25 cm) in 18%
   • Regular (25.1 - 32 cm) in 28%
   • Big (32.1 - 40 cm) in 34%
   • Extra-large (40.1 - 55 cm) in 21%

Findings

1. The research discovered that when a small adult cuff was used, systolic blood pressure measurements were on average 3.6 mm Hg lower than when a conventional adult cuff was used. However, when a normal cuff was used on persons who needed a large adult cuff, systolic readings were on average 4.8 mm Hg higher and 19.5 mm Hg higher in those who required an extra-large cuff based on their mid-arm circumference. The diastolic values followed a trend similar to that of the systolic readings (-1.3 mm Hg, 1.8 mm Hg, 7.4 mm Hg, respectively).
2. It was discovered that using a standard adult cuff resulted in significant variances in blood pressure in all people, which has several therapeutic implications. For example, those who needed an extra-large cuff but were measured with a standard cuff had an average blood pressure of 144/86.7 mm Hg, which is within the range of stage 2 hypertension. However, when the proper size cuff was utilised, the average blood pressure reading was 124.5/79.3 mm Hg, which is within the prehypertensive range.

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Clinical implications

1. Clinicians must place a renewed focus on cuff size, particularly in areas where obesity is rampant and many of their patients need extra-large cuffs since they are the groups most harmed by incorrect cuffing.
2. Overall, the overestimation of blood pressure owing to the use of an insufficiently small cuff misclassified 39% of patients as hypertensive, whereas the underestimating of blood pressure due to the use of an insufficiently big cuff overlooked 22% of people with hypertension.
3. The most current hypertension recommendations outline reasons for error in blood pressure measurement and state that using an incorrect cuff size may result in a difference of 2 to 11 mm Hg in blood pressure readings. That is a big change from previous research and will come as a surprise to physicians.
4. The American Heart Association's 2019 scientific statement on blood pressure measurement emphasises the importance of cuff size, and the American Medical Association launched a new initiative last year to standardise training in blood pressure measurement for future physicians and healthcare professionals.
5. Additionally, previous research has shown that children as young as three to five years of age often need an adult cuff size, while those between the ages of twelve and fifteen may require an extra-large cuff, or what is sometimes referred to as a thigh cuff.

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Logistic errors that need to be addressed

1. A part of the issue is that many doctors are not the ones who perform the measurements and that others may be unfamiliar with certain data and efforts.
2. Additional impediments include cost and availability.
3. Offices and clinics do not commonly keep several cuff sizes in exam rooms, and over-the-counter devices generally have a standard adult cuff.
4. An additional cuff might increase the device's cost in order to accommodate the rising number of patients who measure their blood pressure remotely.

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Illustrations of cuff sizing in relation to the size of a patient's arm

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Position of the body and blood pressure measurement

1. Supine SBP has been found to be 3–10 mm Hg higher than sitting SBP.
2. When measured supine vs. sitting, DBP is 1–5 mm Hg greater.
3. If the arm is lying on the bed in the supine posture, it will be below heart level.
4. When taking blood pressure measures in the supine position, a cushion should be used to support the cuffed arm.
5. When sitting, the right atrium level corresponds to the sternum's midway or the fourth intercostal gap.
6. When a patient's back is not supported (e.g., when sitting on an examination table), SBP and DBP may rise by 5–15 and 6 mm Hg, respectively.
7. Crossing one's legs during blood pressure measurement might increase SBP by 5–8 mm Hg and DBP by 3–5 mm Hg.
8. If the upper arm is below the level of the right atrium (for example, if the arm is hanging down when sitting), the readings will be very high.
9. The observer should support the shackled arm or place it on a table at heart level. If the patient holds his or her arm up, the blood pressure will rise.

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Points to consider while noting the BP reading

1. Arm circumference should be taken at the acromion and olecranon's midway.
2. The bladder length of the blood pressure cuff should be between 75% and 100% of the patient's measured arm circumference.
3. The bladder width of the blood pressure cuff should be between 37% and 50% of the patient's arm circumference (a length-to-width ratio of 2:1).
4. The blood pressure cuff should be applied to exposed skin.
5. Shirtsleeves should not be rolled up to prevent the formation of a tourniquet.
6. The most common inaccuracy in measuring office blood pressure is called "miscuffing," with big arms being under cuffed.
7. Arm circumference should be taken at the acromion and olecranon's midway.
8. The bladder length of the blood pressure cuff should be between 75% and 100% of the patient's measured arm circumference

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References –

1. Muntner P, Shimbo D, Carey RM, Charleston JB, Gaillard T, Misra S, et al. Measurement of blood pressure in humans: A scientific statement from the American Heart Association. Hypertension [Internet]. 2019;73(5):e35–66. Available from: http://dx.doi.org/10.1161/HYP.0000000000000087

2. Program Planner [Internet]. Abstractsonline.com. [cited 2022 Mar 29]. Available from: https://www.abstractsonline.com/pp8/?_ga=2.122166216.21384018.1646150607-715725090.1616603471#!/10553/presentation/491

Disclaimer- The views and opinions expressed in this article are those of the author and do not necessarily reflect the official policy or position of M3 India.

The author is a practising super specialist from New Delhi.