A RANDOMIZED N-OF-1 STUDY COMPARING BLOOD PRESSURE MEASURED ON A CLOTHED ARM AND ON AN ARM WITH A ROLLED-UP SLEEVE

Abstract

Objective: It is recommended that blood pressure (BP) should be measured on a bare upper arm with an appropriately sized cuff. However, in practice, it is more convenient to measure BP on a bare arm below a rolled-up sleeve or on a sleeved arm. A n-of-1 randomized controlled trial was performed to assess the difference between measuring BP over or below a thin rolled-up sleeve. Design and method: The study subject is male, white, 72 years, with BMI 26, arm circumference 29 cm, and under stable antihypertensive treatment. BP was measured 3 times according to guidelines. The order of measurements was determined by chance and 2 devices were used: OMRON HEM-907 and Microlife Afib. 316 measurements needed to be done to detect a difference of 3 mm Hg in systolic blood pressure (SBP). Descriptive statistics and the 2-side T test were used for comparison. Significance was set at the 0.05 level. Results: 504 measurements were performed, 50 % over a sleeve and 50 % on the bare arm below a rolled-up sleeve. The mean SBP was 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, respectively for sleeved and bare arm. 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, difference p = 0.001) mm Hg. There was no significant difference (SBP 118.3 ± 6.8 vs 116.8 ± 5.9, p = 0.97; DBP 68.5 ± 5.5 vs 67.0 ± 5,0 p = 0.44) between measurements over a sleeve and on the bare arm after removing all clothes (n = 96). Conclusions: Blood pressure measurements over a thin sleeve were clinically significantly lower than measurements on a bare arm with rolled-up sleeve and match measurements on a completely bare arm as standard method proposed by guidelines.