By Vijay Kumar MalesuReviewed by Susha Cheriyedath, M.Sc.Oct 8 2024
New research shows that improper arm positioning can inflate blood pressure readings by up to 9 mm Hg, highlighting the urgent need for clinicians to prioritize correct measurement techniques to avoid misdiagnosis and unnecessary treatment.
Arm Position and Blood Pressure Readings - The ARMS Crossover Randomized Clinical Trial. Image Credit: PK289 / Shutterstock
In a recent study published in the journal JAMA Internal Medicine, researchers assessed the impact of different arm positions on blood pressure (BP) readings during clinical measurements.
Background
Hypertension, a major cause of cardiovascular disease and preventable death, requires accurate BP measurement for effective diagnosis and management. Guidelines emphasize correct arm positioning, but this is often overlooked, especially in resource-limited settings. Limited research has focused on the impact of improper arm positioning on BP readings. Further studies are needed to understand the long-term clinical effects and how improper positioning affects different populations and healthcare environments.
About the study
Substantial Overestimation: Unsupported arm positioning can overestimate systolic blood pressure by up to 9 mm Hg in hypertensive patients, leading to potentially significant diagnostic errors.
The present crossover trial was conducted among adults in Baltimore, Maryland. Participants were randomly assigned to undergo BP measurements in three different arm positions: (1) arm supported on a desk at mid-heart level (desk 1, reference), (2) hand supported on the lap, and (3) arm unsupported at the side. Participants also walked for 2 minutes before each BP measurement set to simulate real-world clinical settings. To account for intrinsic BP variability, all participants completed a fourth set of measurements with their arm again supported on a desk (desk 2). Each participant underwent a total of 12 BP measurements (four sets of triplicate measurements).
Eligible participants were adults aged 18 to 80, excluding those with certain medical conditions affecting both arms. Participants were recruited through BP screenings, mailings, brochures, and physician referrals. Self-reported data included age, race, sex, body mass index (BMI), and medical history. The sample size was set to detect clinically meaningful differences, with a target of over 100 participants.
BP measurements were performed by trained staff using a validated oscillometric BP device. To reduce biases, randomization assignments were managed through Research Electronic Data Capture (REDCap). The statistical analysis employed paired t-tests and Bland-Altman plots to compare differences in BP readings across arm positions. Sensitivity analyses explored any impact of unequal participant allocation, as unequal distribution across randomization groups was identified.
Study results
A total of 133 participants were enrolled in the study and randomly assigned to one of six groups based on the order of arm positions used during BP measurements. Each group contained between 12 and 31 participants. The average age of the participants was 57 years, with a standard deviation of 17 years. More than half of the participants were female (53%). Notably, 36% of participants had an SBP of 130 mm Hg or higher, indicating hypertensive BP. Additionally, 41% of participants had a BMI of 30 or higher, indicating obesity and 82% had received healthcare within the past year.
The study analyzed the differences in BP readings across three arm positions: supported on a desk at mid-heart level (desk 1 and desk 2), hand supported on the lap, and arm unsupported at the side. The average systolic blood pressure (SBP) and diastolic blood pressure (DBP) for the desk 1 and desk 2 positions were 126/74 mm Hg. In contrast, the lap position resulted in an average BP of 130/78 mm Hg, while the side position showed even higher readings at 133/78 mm Hg. The differences between the two desk positions were negligible: a mean SBP difference of -0.21 mm Hg and a DBP difference of 0.09 mm Hg.
Importance of Awareness and Training: The study emphasizes that lack of awareness about proper arm positioning among healthcare providers contributes to diagnostic inaccuracies, suggesting the need for improved training and standardization in BP measurement practices.
When analyzing the differences between the desk 1 reference and the other positions, the lap position resulted in a mean SBP increase of 3.9 mm Hg and a DBP increase of 4.0 mm Hg. The side position showed even greater differences, with a mean SBP increase of 6.5 mm Hg and a DBP increase of 4.4 mm Hg. These findings were statistically significant and were further confirmed by Bland-Altman plots, which demonstrated consistent BP variation across different arm positions.
Subgroup analyses indicated that the results were generally consistent across various participant groups. Participants with an SBP of 130 mm Hg or higher experienced an even larger BP increase of approximately 9 mm Hg in the side position. Additionally, participants who had not received healthcare in the past year exhibited a statistically significant larger BP increase in the lap position compared to those who had received recent healthcare.
Sensitivity analyses were conducted to address potential limitations in the randomization procedure. These analyses produced results similar to the primary analysis, confirming the robustness of the findings.
Conclusions
This randomized crossover trial demonstrates that arm positioning significantly affects BP readings. Measurements taken with the arm on the lap or unsupported at the side result in higher BP compared to proper arm support at the heart level, leading to overestimation by 4 to 7 mm Hg. For individuals with hypertensive BP, the overestimation can be as high as 9 mm Hg when the arm is unsupported at the side. These findings highlight the risk of hypertension misdiagnosis and overtreatment in clinical practice. Ensuring correct arm positioning during BP measurement is crucial for accurate diagnosis and effective management of hypertension.