under pressure
Before participants took measurements in either position, the researchers had participants simulate walking to a doctor’s appointment. They walked for 2 minutes and then sat quietly in place for 5 minutes before taking three measurements. They stood up, walked again, and sat for another 5 minutes before moving to the next position. Participants were also randomly assigned to groups that performed the first three measurements (Desk 1, Lap, Side) in different orders, with all groups finishing at Desk 2.
The researchers then compared the difference between Desk 1 and Desk 2 for each participant to the difference between Lap and Desk 1 and Side and Desk 1. The difference between desk 1 and desk 2 captured the inherent variability in blood pressure measurements for each participant. A comparison between Lap Desk 1 and Side Desk 1 captured changes due to incorrect arm position.
Overall, there was little difference between Desk 1 and Desk 2, with participants having a mean difference of -0.21 mm Hg in systolic blood pressure and 0.09 mm Hg in diastolic blood pressure. However, incorrect arm position significantly affected the measurements. The wrap arm position increased both systolic and diastolic measurements by an average of 4 mm Hg. Side arm position resulted in systolic readings being 6.5 mm Hg higher and diastolic readings being 4 mm Hg higher. For those with high blood pressure readings, about 36 percent of participants, incorrect arm position caused readings to be even higher, with systolic readings about 9 mm Hg higher than desk readings.
The authors speculate that a simple physiological mechanism likely explains the increase in blood pressure when the arm is lower than the heart. Increased gravity, compensatory contraction of blood vessels, and contraction of muscles can lead to increased blood pressure. As for why healthcare providers are known to sometimes use such incorrect arm positions, it may be due to a lack of awareness, training, equipment, and/or resources.
The authors of this study call for further training and education on proper blood pressure measurement, which is essential for proper management of hypertension and prevention of cardiovascular disease.
