A randomized n-of-1 study comparing blood pressure measured on a clothed arm and on an arm with a rolled-up sleeve

Abstract

Background: Blood pressure [BP] should be measured using a bare upper arm with an appropriately sized cuff. In practice, it is more convenient to measure BP on a bare arm below a rolled-up sleeve or on a sleeved arm.

Aim: A n-of-1 randomized controlled trial was performed to assess the difference between BP measurements over a sleeve or below a rolled-up sleeve.

Methods: The study subject was male, white, 72 years old, BMI 26 kg/m2, arm circumference 29 cm, and under stable antihypertensive treatment. The mean of three BP measurements over a thin sleeve was compared with measurements below a rolled-up sleeve. Additional measurements on a completely bare arm, with thicker sleeves and up to three layers were performed. The order of measurements was determined by chance and two oscillometric devices were used. Descriptive statistics, Bland-Altman test and 2-side T test were used for comparisons.

Results: 504 measurements were performed: 50 % over the sleeve and 50 % below the rolled-up sleeve. The mean systolic blood pressure (SBP) was respectively 116.9 ± 9. 2 [95% CI 115.7-118.0, range 96-135] and 122.8 ± 9.2 [95% CI 121.7-124.0, range 103-139, p = 0.001] mm Hg. The mean diastolic blood pressure [DBP] was respectively 67.6 ± 6.8 [95% CI 66.8-68.4, range 52-84] and 71.8 ± 6.8 [95% CI 71.0-72.7, range 55-85, p = 0.001] mm Hg. There was no significant difference between the measurements over the sleeve and on the completely bare arm [n = 94, p = 0.97]. Sleeve thickness with 2 layers up to 3 mm thick did not affect the results.

Conclusions: Blood pressure measurements over a thin sleeve were significantly lower than measurements below a rolled-up sleeve and match measurements on a completely bare arm.

Keywords: Hypertension; N-of-1 trial; blood pressure measurement; clothing.