A recent study suggests that incorrect arm position during blood pressure checks can lead to misdiagnosis and overestimation of hypertension.
Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels. The measurement unit is mmHg. The reading is composed of two numbers: the upper (systolic) value first, followed by the lower (diastolic) value. A person is deemed hypertensive if their blood pressure measurements are consistently 130/80 or higher.
The new study, published on Monday in Journal JAMA Internal Medicine, analysed the blood pressure readings of 133 adults from August 2022 to June 2023. The study volunteers’ ages ranged from 18 to 80.
Blood pressure readings were taken and compared while people held their arms in three distinct positions: leaning on a surface, resting on their laps, and hanging by their sides.
The researchers from Johns Hopkins University discovered that when participants had their arms hanging by their sides during the reading, their systolic pressure was 6.5 points higher than when their arms were resting on a desk, while their diastolic blood pressure — the bottom number — was 4.4 points higher than in the supported position.
The specialists also discovered that while their arms were on their laps, their systolic blood pressure was 3.9 points higher than when they were supported by a surface, and their diastolic pressure was 4 points higher.
For example, if a person’s actual blood pressure is 134 and blood pressure is measured with a dangling arm, the measurement may exceed 140, indicating stage 2 hypertension.
Tammy Brady, vice-chair for clinical research in the department of pediatrics at the Johns Hopkins University School of Medicine, stated that the two other positions were evaluated after it was discovered that they are the most commonly used positions during blood pressure measurements.
“I did not expect there to be that much of a difference when the arms were placed in the two alternative positions,” he said.
“We tested those positions because those are the positions that most people have their blood pressure measured, according to data and personal observations.
“We thought there’d be a difference, but I was surprised by how much of a difference there was.”
According to the study, the wrong positioning of the arm during BP readings leads to overestimation due to several physiological reasons.
First, there can be muscle contraction when the arm is not supported which can lead to an increase in BP reading.
Also, a greater vertical distance between the heart and where the cuff is placed can increase hydrostatic pressure in the arteries, or the blood pressure against the wall due to gravity’s pull. This can lead to an overestimation of blood pressure.
Brandy said the study was conducted to educate people on the appropriate arm position for BP reading.
“I just hope that it raises awareness regarding how important things like arm position are to blood pressure measurement accuracy,” he added.
“I also hope this study educates patients, empowering them to advocate for proper measurement when they’re in a clinic setting.
“But also, because so many patients rely on home blood pressure measurements for hypertension diagnosis, evaluation, and treatment.
“I hope this educates them on how to properly position their arms because our findings absolutely extend to measurements in the home.”
The researchers also gave the following steps to achieve an accurate BP measurement.
The steps include:
- Wear the appropriate cuff size
- Have your back supported
- Keep feet flat on the floor with legs uncrossed
- Have the appropriate arm position – the cuff should be positioned at heart level with the arm supported on a desk or table
Wearing the correct cuff size was determined to be the most significant step.
Improperly sized blood pressure cuffs can affect readings from automated systems.
Also speaking, Gail Adler, a cardiovascular endocrinologist in the Hypertension Clinic at Brigham and Women’s Hospital, revealed several steps that should take 30 minutes for blood pressure testing.
“Before you take your blood pressure, you want no smoking, exercise, caffeine, alcohol, major arguments. Don’t be psychologically stressed,” Adler said.
“Sit in the chair, get in the right position. And for five minutes, you relax, you don’t talk, make sure you don’t have to pee. If you have to pee or urinate, that’s going to raise your blood pressure.”