Incorrect positioning of your arm during a blood pressure check can lead to inaccurate results, potentially affecting diagnosis and treatment decisions. A new study recently published in JAMA Internal Medicine highlights just how crucial the proper arm alignment is for an accurate reading.
Arm placement matters for accurate results
Proper blood pressure readings require the arm to be positioned at heart level and supported on a flat surface. Failing to do so may cause measurements to be artificially high. Researchers have found that incorrect arm positioning, such as resting the arm on a lap or letting it hang at the side, can mislead healthcare professionals into misdiagnosing patients with high blood pressure.
Dr. Tammy Brady, a senior study author and vice chair for clinical research at Johns Hopkins University School of Medicine, explains: “Because home measurements are an important part of the diagnosis, it is essential to properly educate patients on blood pressure measurement technique, as inaccurate readings may contribute to a misdiagnosis or inappropriate choice in therapy.”
Which positions cause inaccuracies?
The study found that 16% of U.S. adults could be misclassified with high blood pressure if their arm wasn’t properly positioned. This includes instances where people rest their arm on their lap or let it hang at their side instead of keeping it flat and at heart level.
The research showed significant discrepancies in measurements depending on arm placement. For example, resting the arm on a lap resulted in systolic blood pressure readings overestimated by 3.9 mmHg, and diastolic pressure by 4 mmHg. Arms hanging at the side increased systolic readings by 6.5 mmHg and diastolic readings by 4.4 mmHg. Dr. Gregory Katz, a cardiologist at with NYU Langone Health, emphasizes the importance of accurate measurements: “Even though those numbers sound low, they can make a real difference in putting someone on medicine or not putting someone on medicine, or increasing the dose of a medicine versus keeping it the same.”
Why is arm positioning so critical?
When the arm is improperly positioned, gravity plays a key role in raising the blood pressure reading. Dr. Brady expounds that when the arm is positioned lower than the heart, the blood vessels are farther away, and gravity causes increased pressure in these vessels. Moreover, the lack of support causes muscle tension, which further contributes to inaccurate readings. “In addition, when the arm is unsupported, the muscle isn’t fully at rest and contracts. All of these body responses lead to a higher BP [blood pressure] reading,” Dr. Brady says.
Ensuring an accurate reading
To ensure an accurate blood pressure check, the American Heart Association recommends sitting with a straight back and your feet flat on the floor. The cuff should also fit properly and be placed on the correct part of the arm. A cuff that is too small can overestimate systolic pressure by as much as 10 to 20 mmHg.
Dr. Katz urges healthcare professionals to adopt best practices when measuring blood pressure: “The only way to control blood pressure well is to know what the actual value is.”
Important points to remember
In conclusion, remember that to avoid inaccurate readings, consider these key points:
- Incorrect arm positioning can result in falsely elevated blood pressure readings.
• For the most accurate results, keep your arm supported on a flat surface and aligned with heart level.
• Mispositioning your arm may lead to misdiagnosis and improper treatment decisions.
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