The results obtained when measuring blood pressure may not be accurate if the arm is not in the correct position, suggests a new study published Monday in the journal JAMA Internal Medicine.
A comparison of readings taken with the arms positioned in three different ways (resting on a surface, on the lap or hanging at the side of the body) showed that certain positions could cause a significant increase in systolic pressure, the upper value of blood pressure. blood pressure reading, which refers to the pressure in a person’s arteries when the heart sends blood throughout the body.
How big the difference was, almost 7 points if the arm was hanging, was a surprise, said the study’s lead author, Tammy Brady, a pediatrician, epidemiologist and director of the pediatric hypertension program at Johns Hopkins Children’s Center.
The researchers weren’t sure what to expect when conducting their experiment. “There was a possibility that the position of the arms was not important,” Brady said. “One of my hopes is that this will help educate patients on how to do it on their own and also communicate it to their provider in the right way,” Brady said. “Patients should be empowered to ensure that their blood pressure measurement is accurate,” he added.
The American Heart Association recommends supporting the patient’s arm to get an accurate reading. Besides:
- Avoid caffeine, exercise or smoking for 30 minutes.
- The blood pressure monitor should be placed at the height of the middle of the heart.
- The patient’s feet should be flat on the floor with the back in good posture.
Nearly half of adults in the United States suffer from high blood pressure, which occurs when the average strength of the blood is higher than what is considered normal: less than 120 systolic pressure and less than 80 diastolic pressure (the pressure in the arteries between heartbeat). Hypertension has mild symptoms, but if left untreated it can increase the risk of stroke, heart attack, and other serious cardiovascular conditions.
To find out if arm position influenced blood pressure values, Brady and his colleagues recruited 133 adults, 78% of them black and 52% of them women. The age of the volunteers ranged from 18 to 80 years.
Although all participants had their blood pressure measured in all three arm positions, they were randomly assigned to one of six possible groups that differed in the order in which the positions were adopted.
The researchers found that when people had their arms hanging at their sides while reading, their systolic blood pressure was 6.5 points higher than when they had their arms resting on a desk, while their diastolic blood pressure (the bottom number) was 4.4 points. higher than in the other position.
Similarly, when people had their arms on their lap, systolic blood pressure was 3.9 points higher than when they rested their arms on a surface, while diastolic pressure was 4 points higher than when the arm was supported.
These differences could increase the number of hypertension diagnoses and lead patients to be prescribed medications they do not need.
For example, if a person’s actual blood pressure is 134, and it is measured with an arm hanging, the reading could end up above 140, which is considered grade 2 hypertension.
Mispositioning a patient’s arm “is unfortunately a common experience,” said Dr. Karyn Singer, a professor of medicine at New York University and associate vice president of chronic diseases and prevention at NYC Health + Hospitals.
“As a patient, I’ve been through that,” he explained. The study provides “evidence that is really critical,” said Singer, who was not involved in new research: “Until now it was unclear to what extent arm position modifies blood pressure readings.”
Singer said patients should “be aware of the correct technique for measuring blood pressure and advocate for themselves if they believe the value read is higher than they think it should.”
As a patient, Dr. Megan Kamath has also had similar experiences in different health centers and offices.
“There is a pretty significant difference in blood pressure readings depending on the position of the arm,” said Kamath, a cardiologist at UCLA Health.
“This is a fascinating study,” said Kamath, who was also not involved in the research. “My takeaway from reading it was, wow, with a simple study design these researchers found some important real-world implications that can make the difference between a patient receiving treatment for hypertension or not,” he said.
Those who receive blood pressure-lowering treatment that they do not need may suffer side effects, such as lightheadedness, dizziness, fatigue and blurred vision, according to Singer.
The study’s findings support patients asking their doctor to measure their blood pressure “the right way,” said Dr. Matthew Tomey, a cardiologist at Mount Sinai Fuster Heart Hospital in New York. The differences found could be enough to move someone from one blood pressure category to another, said Tomey, who was also not involved in this new study.
