Scientific Asia: Checking blood pressure at home? Don’t overlook your arm position.
A recent study found that improper arm position affects blood pressure readings. They are “markedly higher” than when the arm is properly supported on a table, with the cuff at heart level.
If your arm is not supported and positioned correctly during a blood pressure reading, it may cause a false positive for high blood pressure. Some doctors worry this may lead to unnecessary treatment.
A JAMA Internal Medicine study found that measuring blood pressure with your arm in your lap overestimates the systolic and diastolic readings by 3.9 and 4 mm Hg, respectively. Also, hanging your arm by your side can overestimate your blood pressure. It can raise the diastolic reading by 4.4 mm Hg and the systolic by 6.5 mm Hg.
The upper, or systolic, reading and the lower, or diastolic, reading make up the blood pressure measurement. It is in millimeters of mercury or mm Hg. If a person’s blood pressure consistently measures 130/80 or greater, they are diagnosed with hypertension, also known as high blood pressure.
“Healthcare providers should be reminded of the importance of doing these steps correctly,” said Dr. Tammy Brady. She is the study’s senior author and medical director of the pediatric hypertension program at Johns Hopkins Children’s Center. She is also the pediatrics department’s vice chair for clinical research at the Johns Hopkins University School of Medicine.
Brady expressed his hope that the study would increase awareness of the significance of arm position in blood pressure measurement accuracy.
She added, “I hope this study empowers patients to advocate for proper measurement in clinics by educating them. I also hope it informs them about arm positioning. Many rely on home blood pressure readings to diagnose and assess hypertension.” Our findings are unquestionably applicable to readings taken at home.
From August 2022 to June 2023, Johns Hopkins researchers chose 133 adults from Baltimore, Maryland, to take part in a study. Participants, aged 18 to 80, were randomly divided into three groups. They were asked to have their blood pressure taken with their arms supported in one of three ways: on a desk (the recommended method), on their lap, or hanging unsupported by their sides.
We measured each subject’s blood pressure a total of twelve times while their arms were in those different configurations.
The average blood pressure reading among the participants was 126/74 while their arms were supported on a desk, as advised by the accepted therapeutic recommendations, the researchers discovered.
However, the average blood pressure reading for the individuals was 130/78 when their arms were resting in their laps and 133/78 when they were hanging their arms by their sides.
“When the arms were positioned in the two different ways, I did not think there would be such a noticeable difference. “Based on data and observations, we examined those locations. That’s where most people get their blood pressure checked,” Brady explained. “We anticipated a difference, but I wasn’t prepared for the magnitude of that difference.”
According to the researchers, when the arm is not properly positioned or supported, blood pressure readings may be erroneously higher for several physiological reasons. An overestimation of blood pressure can result from increased hydrostatic pressure in the arteries. This is the force of blood against the artery walls, caused by gravity. It occurs if there is a larger vertical distance between the heart and the cuff. Additionally, an unsupported arm may induce a muscle contraction that raises blood pressure.
A Guide to Accurately Measuring Blood Pressure
The results of the present study align with other independent earlier studies that demonstrated overestimation of a blood pressure reading can occur when an arm is positioned below heart level or in an unsupported arm position.
An email from Dr. Nichola Davis at NYC Health and Hospitals stated, “We know that arm position affects blood pressure. This study measures how much it impacts the reading.” Davis was not involved in the study.
Participants with elevated blood pressure exhibit this more than those with lower blood pressure, but it is present in all of them.
These are significant results since blood pressure readings are the basis for both diagnosis and treatment of hypertension, and they must be reliable, according to Davis’ email.
According to the study’s findings, the “latest clinical practice guidelines emphasize several key steps for accurate measurement,” which include the following:
- Put on the proper-size cuff.
- Make sure your back is supported.
- Keep your legs straight and your feet flat on the ground.
- Maintain the proper arm position by resting your arm on a desk or table and positioning the cuff at heart level.
Wearing the right-sized blood pressure cuff is important. An incorrectly sized cuff can skew the numbers from automated blood pressure monitors. One study found that if a patient needed a different-sized blood pressure cuff, regular-sized ones gave “strikingly inaccurate” readings. This was especially true for those who fit larger cuffs. The study was published in the journal JAMA Internal Medicine last year.
Before having their blood pressure taken, people should do a few things. This is according to Dr. Gail Adler, a cardiovascular endocrinologist at Brigham and Women’s Hospital. She is a co-specialist in the hospital’s hypertension clinic. She was not involved in the current study.
“You want to avoid smoking, exercising, coffee, alcohol, and large disputes in the half an hour before taking your blood pressure. Avoid experiencing psychological stress, Adler said.
Next, sit in the chair. Adjust to your desired posture. Then, for five minutes, sit up straight. Relax. Don’t talk. Rest your arms. Keep your legs uncrossed and your feet flat on the ground. Assemble no urine or need to urinate; this may cause your blood pressure to rise, the woman advised.
According to research, blood pressure taken at home is a better estimate of a person’s usual blood pressure than blood pressure taken at an office since people feel more at ease and relaxed there, according to Adler.
In 20% to 45% of cases, blood pressure tests are “suboptimally performed.” This can cause inaccuracies that wrongly influence doctors’ recommendations for controlling a patient’s blood pressure.
All of us on the research team, anecdotally, have, I believe, begun to pay closer attention to how our blood pressure is taken. Brady stated, “I have paid attention to the way my children’s blood pressure is taken.”
Let’s be careful not to judge too quickly
Elevated blood pressure increases the likelihood of heart disease and stroke, the two biggest killers in the US.
Nearly half of American adults are thought to have high blood pressure. But, only about one in four of them have it under control, according to the CDC.
Dr. Dave Montgomery, a cardiologist at Piedmont Healthcare in Atlanta, is not involved in the current study. He stated via email that he believes Americans do not treat hypertension aggressively enough.
Hypertension is a major risk factor for cardiovascular disease. It’s also one of the easiest conditions to manage. He stated that hypertension causes many heart diseases and deaths. “We don’t always hit the mark.”
He continued with a reference to the recent study. He did not see a blood pressure reading that could be inaccurate by 4 to 5 mm Hg due to arm posture. This could lead to overdiagnosis or overtreatment, like a prescription change or dose adjustment.
A 4 mmHg increase won’t affect someone whose blood pressure is normal. Montgomery stated that if a person has been diagnosed with hypertension, a score of 5 to 10 may indicate that they are not quite in control of their condition. It can change every minute, depending on a person’s mood and physical state, he continued.
Consequently, we should not, in general, conclude too quickly from a single blood pressure measurement. Nonetheless, vigorous treatment for persistently elevated blood pressure is necessary, he noted. The burden of heart disease can be reduced in this way.
