Wrong BP cuff size could cause inaccurate BP measurement
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Using a regular-sized BP cuff for all adults regardless of mid-arm circumference can result in “striking” differences in systolic and diastolic BP, possibly leading to an incorrect hypertension diagnosis, researchers reported.
“Accurate BP measurement to screen for hypertension is one of the best ways we can help decrease the burden of hypertension and CVD worldwide. We know there are many steps one must take to get an accurate BP measurement, but some of those steps have not been systematically tested to see how important they are to accuracy,” Tammy M. Brady, MD, PhD, vice chair for clinical research in pediatrics and associate professor of pediatrics in the division of pediatric nephrology and medical director of the Pediatric Hypertension Program at Johns Hopkins University School of Medicine, told Healio. “We looked at those steps and thought that 'miscuffing,' meaning, using a BP cuff that is not the right size for one's arm, was one of the bigger barriers to accuracy. In clinic settings, oftentimes whatever cuff happens to be on the BP device is what is used for each patient.”
Accurate BP measurement depends on proper patient preparation, positioning, measurement technique and individualized selection of cuff size, which should be based on the measured mid-arm circumference, Brady and colleagues wrote in an abstract. Clinical practice guidelines highlight the importance of individualized BP cuff selection for measuring BP; however, most of the research looking at cuff size on measurement accuracy was done using mercury sphygmomanometers, Brady said.
“We conducted a literature review and found that none of the studies that informed this recommendation to individualize cuff selection based on arm size used automated BP devices, which is what is used in clinical settings,” Brady told Healio. “We wanted to see if using a regular adult-size cuff for all-comers made a difference in measured BP. What we found was it made a huge difference.”
In a randomized, crossover trial, Brady and colleagues analyzed data from 165 adults who underwent two sets of triplicate BP measurements using a regular adult cuff and an appropriate cuff, in random order. Cuff-size subgroups were defined as small adult (20-25 cm); regular adult (reference; 25.1-32 cm); large adult (32.1-40 cm) and extra-large adult (40.1-55 cm). The mean age of participants was 55 years, 33% were men and 68% were Black. Researchers sought to determine the effects of using a regular adult BP cuff compared with a BP cuff that is appropriately sized for a person’s mid-upper arm circumference.
Within the cohort, 30% of participants had systolic BP of at least 130 mm Hg and 42% had a BMI of at least 30 kg/m2. Among participants who required a small adult cuff, a regular cuff resulted in lower systolic BP readings (mean, –3.8 mm Hg; 95% CI, –6.3 to –1.3) and lower diastolic BP readings (mean, –1.5 mm Hg; 95% CI, –3 to 0).
In contrast, among participants who required a large adult cuff, a regular cuff was associated with a mean 4.8 mm Hg higher systolic BP reading (95% CI, 2.9-6.7; P < .0001). For those who required an extra-large adult cuff, a regular cuff was associated with a mean 19.7 mm Hg higher systolic BP reading (95% CI, 16.3-23.2; P < .0001).
The overestimation of BP due to “undercuffing” misclassified 39% of participants with a hypertensive BP, defined as 130/80 mm Hg, whereas the underestimation of BP due to “overcuffing” missed 22% of participants with a hypertensive BP, according to the researchers.
“We expected to see a difference but did not expect the degree that we found,” Brady said in an interview. “The fact that using a regular BP cuff for people who need an extra-large cuff can cause someone to overestimate BP by 20 mm Hg is striking and can lead to imprecise diagnoses and potential overtreatment.”
Brady said a renewed emphasis on cuff size is warranted, particularly in populations with high prevalence of obesity requiring large or extra-large cuff sizes.
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Brady TM, et al. Abstract EP-01. Presented at: Epidemiology, Prevention, Lifestyle & Cardiometabolic Scientific Sessions; March 1-4, 2022; Chicago.
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