RCT: Nonstandard Arm Positions Overestimate Blood Pressure Readings in Adults
12 Oct, 2024 | 22:55h | UTCBackground: Accurate blood pressure (BP) measurement is crucial for the diagnosis and management of hypertension, a leading cause of cardiovascular disease and mortality worldwide. Guidelines recommend measuring BP with the arm supported on a desk at heart level. However, in clinical practice, nonstandard arm positions—such as resting the arm on the lap or having it unsupported at the side—are commonly used, potentially leading to inaccurate readings.
Objective: To determine the effect of commonly used nonstandard arm positions on BP measurements compared to the standard, recommended position.
Methods: In a crossover randomized clinical trial from August 2022 to June 2023, 133 adults aged 18 to 80 years were recruited. Participants were randomly assigned to receive sets of triplicate BP measurements with the arm in three positions: (1) supported on a desk with the midcuff at heart level (desk 1; reference), (2) hand supported on the lap (lap), and (3) arm unsupported at the side (side). To account for intrinsic BP variability, all participants underwent a fourth set of BP measurements with the arm supported on a desk (desk 2). The primary outcomes were the difference in differences in mean systolic BP (SBP) and diastolic BP (DBP) between the reference BP (desk 1) and the two nonstandard arm positions (lap and side).
Results: Among 133 participants (mean age 57 years; 53% female), 36% had SBP ≥130 mm Hg, and 41% had a body mass index ≥30 kg/m². Compared to the reference position, the lap and side positions resulted in significantly higher BP readings. The difference in differences for the lap position was an increase in SBP of 3.9 mm Hg (95% CI, 2.5-5.2) and DBP of 4.0 mm Hg (95% CI, 3.1-5.0). For the side position, the increases were SBP 6.5 mm Hg (95% CI, 5.1-7.9) and DBP 4.4 mm Hg (95% CI, 3.4-5.4). These patterns were consistent across subgroups.
Conclusions: Commonly used nonstandard arm positions during BP measurements, such as resting the arm on the lap or having it unsupported at the side, significantly overestimate BP readings compared to the standard recommended position. This overestimation may lead to misdiagnosis and overestimation of hypertension.
Implications for Practice: Clinicians should adhere to guideline-recommended arm positioning during BP measurements to ensure accurate readings. Proper arm support with the midcuff at heart level is necessary to avoid overestimation of BP, which can result in unnecessary follow-up and overtreatment due to hypertension overdiagnosis.
Study Strengths and Limitations: Strengths include the randomized crossover design ideal for studying BP differences, a larger sample size than previous studies, and focus on arm positions commonly used in clinical practice with an automated BP device. Limitations include unequal randomization due to the randomization function used, small sample sizes in some subgroups, and uncertain generalizability to other settings or devices.
Future Research: Further studies are needed to investigate strategies to improve adherence to guideline-recommended arm positions in clinical practice, assess the impact of educational interventions on BP measurement accuracy, and explore the effects of arm position on BP readings using different devices or in diverse populations.