Certain Arm Positions Can Distort BP Readings, Urging Need for Standardization: ARMS Trial

The findings demonstrated that frequently adopted arm positions (resting on the lap or hanging by the side) significantly inflated blood pressure readings, potentially leading to misdiagnosis and an exaggerated assessment of hypertension.

Guidelines for BP measurement advise supporting the arm on a desk, with the midcuff aligned at the heart level. However, nonstandard positions—such as resting the arm on the lap or leaving it unsupported at the side—are still commonly utilized in clinical practice. In light of this, Hairong Liu, Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, and colleagues aimed to assess the impact of various arm positions on blood pressure readings.

For this purpose, the researchers conducted a crossover randomized clinical trial in Baltimore, Maryland, enrolling adults aged 18 to 80 from August 9, 2022, to June 1, 2023. Participants were randomly assigned to undergo three sets of blood pressure measurements with their arms positioned in three ways: (1) supported on a desk (desk 1, reference), (2) hand resting on the lap (lap), and (3) unsupported at the side (side). To account for natural BP variability, each participant had a fourth set of measurements with the arm supported on a desk (desk 2).

The primary outcomes were the differences in mean systolic and diastolic blood pressure between the reference position (desk 1) and the other two positions (lap and side), calculated as (lap or side - desk 1) - (desk 2 - desk 1). Results were further analyzed based on hypertensive status, age, obesity, and healthcare access in the past year.

The following were the key findings of the study:

• The trial enrolled 133 participants (mean age, 57 years; 53% female); 36% of participants had SBP of 130 mm Hg or higher, and 41% had a body mass index (calculated as weight in kilograms divided by height in meters squared) of 30 or higher.
• Lap and side positions resulted in statistically significant higher BP readings than desk positions, with the difference in differences as follows: lap, SBP Δ 3.9 mm Hg and DBP Δ 4.0 mm Hg; and side, SBP Δ 6.5 mm Hg and DBP Δ 4.4 mm Hg.
• The patterns were generally consistent across subgroups.

"The findings imply that frequently used, nonstandard arm positions during blood pressure measurements significantly inflate BP readings, underscoring the necessity for standardized positioning," the researchers concluded.

Reference:

Liu H, Zhao D, Sabit A, et al. Arm Position and Blood Pressure Readings: The ARMS Crossover Randomized Clinical Trial. JAMA Intern Med. Published online October 07, 2024. doi:10.1001/jamainternmed.2024.5213