Using an incorrectly sized cuff to measure blood pressure (BP) can result in inaccurate readings leading to either undertreatment or overtreatment, according to a preliminary results from the Cuff Size Blood Pressure Measurement “Cuff(SZ)” trial presented at the ongoing Epidemiology, Prevention, Lifestyle & Cardiometabolic Health Conference 2022 in Chicago.¹

The BP readings of 165 adults were analysed for this trial. The average age of the participants was 55 years and more than 40% of the participants were obese with BMI of ≥30kg/m². Three consecutive BP readings were recorded with an automated and validated device in a quiet room at a gap of 30 seconds. Before each measurement, the participants walked a similar distance for 2 minutes from a waiting area to the room where BP was measured after 5 minutes of rest to eliminate the impact of longer resting time on the readings. They were also instructed to remain silent and not use their smartphones during this entire procedure. Researchers then compared the average of three BP readings using a regular adult-sized cuff against the average of three BP readings with an appropriately sized cuff. “Based on arm circumference (mean, 34 cm), the appropriate adult cuff size was small (20-25 cm), regular (25.1-32 cm), large (32.1-40 cm) and extra-large (40.1-55 cm).”

Analysis revealed that the systolic BP was ≥130mmHg in 30% of participants. Using a regular sized adult cuff in individuals who required a small adult cuff size led to average 3.8 mm Hg lower systolic BP reading as well as 1.5 mmHg lower diastolic BP reading.

On the other hand, the systolic BP reading was 4.8 mm Hg (average) higher when BP was measured with a regular sized cuff in individuals who required a large or extra-large cuff size; the systolic BP was 19.7 mmHg higher with the use of regular cuff size in those who required extra-large cuff size. A similar trend was noted for the diastolic BP; 1.8 mm Hg and 7.4 mm Hg, respectively.

When a regular adult cuff was used in persons who needed an extra-large cuff, their average BP reading was 144.9/86.5 mm Hg, which could be diagnosed as stage 2 hypertension. But when BP was measured with the right sized cuff, their average BP reading was 124.2/79.1 mm Hg, which is in the prehypertensive range. Overall, 39% of the participants were incorrectly diagnosed as hypertensive by using a smaller than appropriate sized cuff. Similarly, using a large/extra-large cuff missed 22% of participants with hypertension.

This study highlights that there is no one size that fits all. Using just one cuff size in OPDs or clinics to measure BP may result in erroneous BP readings and misdiagnosis, particularly in the obese individuals who need a large or extra-large cuff size for accurate BP measurement. Physicians should be aware about the implications of using an inappropriately sized cuff for BP measurement. The mid-arm (midpoint between the shoulder and elbow) circumference can be used to select the right-sized cuff as also recommended by the American Heart Association (AHA).

The AHA has listed seven common mistakes while measuring BP that could lead to erroneously high BP reading and an inaccurate diagnosis of hypertension. These include measuring BP in a person with a full bladder, sitting slouching with unsupported arm, back or feet, sitting with crossed legs, answering questions and talking on the phone, wrapping the cuff over clothing and using a too small cuff.

Reference

1. Brady TM, et al. One size does not fit all: impact of using a regular cuff for all blood pressure measurements. Abstract EP01. EPI/Lifestyle 2022. Presented March 1, 2022.