Agreement between large and small cuffs in sphygmomanometry: a quantitative assessment

The objective of this study is to quantify agreement and differences between blood pressure (BP) measurements by large cuffs (15 x 33 cm) and small cuffs (12 x 23 cm) in a representative sample of the U.S. population with varying arm circumferences.

The arm circumference and blood pressure (12 readings of each) of 85 subjects were measured, the latter with a mercury column sphygmomanometer. Data were classified according to arm circumference (small arm circumference, < or = 29 cm; large arm circumference, > 29 cm). Results were submitted to ANOVA, linear regression, difference between means (aggregate agreement), upper and lower limits of agreement at 95% confidence intervals, and intraclass correlation (individual-subject agreement/quantification of agreement).

Small cuffs overestimated BP obtained from the large cuffs for the sample population as a whole, regardless of arm circumference. Limits of agreement at the lower end of 95% confidence interval were not clinically acceptable (SBP -1.56 to 11.05 mm Hg; DBP -2.06 to 8.63 mm Hg). However, measurements by both cuffs agreed among subjects with small arm circumferences (< or = 29 cm).

Arm circumference plays an important role in determining proper cuff size for BP measurement. The small cuff overestimates BP in patients with large arm circumferences (> 29 cm), which represents more than 75% of the U.S. adult population. However, measurements of BP with the large cuff are not significantly different from those of small cuff measurements in subjects with small arm circumferences (< or = 29 cm). Therefore, we propose that the large cuff be used for routine BP measurement of the adults in the United States.