A new study published in JAMA Internal Medicine highlights the importance of proper arm positioning during blood pressure measurements. The research indicates that common non-standard arm positions, such as resting the arm on the lap or holding it unsupported at the side, can lead to significant overestimation of blood pressure (BP) readings, potentially resulting in misdiagnosis and overtreatment of hypertension.
The crossover randomized clinical trial, conducted by researchers at Johns Hopkins, involved 133 adults aged 18 to 80 years. Participants underwent triplicate BP measurements in three different arm positions: supported on a desk (reference), supported on the lap, and unsupported at the side. A fourth set of measurements with the arm supported on a desk was also taken to account for BP variability.
The results showed that both lap and side positions led to statistically significant higher BP readings compared to the desk position. Specifically, supporting the arm on the lap overestimated systolic BP by 3.9 mm Hg (95% CI, 2.5-5.2) and diastolic BP by 4.0 mm Hg (95% CI, 3.1-5.0). The unsupported arm at the side overestimated systolic BP by 6.5 mm Hg (95% CI, 5.1-7.9) and diastolic BP by 4.4 mm Hg (95% CI, 3.4-5.4).
Implications for Clinical Practice
These findings underscore the need for healthcare providers to adhere to established guidelines for BP measurement, which recommend that the arm be supported at heart level. According to the American Heart Association (AHA), the blood pressure cuff should be positioned at mid-heart level on an arm that is supported on a desk or table. Sherry Liu, an epidemiology research coordinator at Johns Hopkins Bloomberg School of Public Health, noted that an overestimation of 6.5 mmHg could be the difference between a systolic BP of 123 and 130, or 133 and 140, the latter being considered stage 2 hypertension.
Study Details and Limitations
The study participants included a diverse group of adults, with 36% having a systolic BP of 130 mm Hg or higher and 41% having a body mass index of 30 or higher. The researchers accounted for intrinsic BP variability by including a fourth set of measurements with the arm supported on a desk. However, the authors noted that their results may only apply to screenings with automated blood pressure devices.
Call for Standardized Positioning
Tammy Brady, vice chair for clinical research in the department of pediatrics at Johns Hopkins University School of Medicine, emphasized the importance of standardized positioning during BP measurements. "Patients must advocate for themselves in the clinical setting and when measuring their BP at home," Brady stated. The study highlights a potential source of error in BP measurement that could lead to unnecessary treatment and increased healthcare costs. By ensuring proper arm positioning, clinicians can improve the accuracy of BP readings and provide more appropriate care for their patients.
