Blood pressure is one of the most common health checks, but researchers now say that the way it’s usually measured might not be as accurate as we think.
Scientists from the University of Cambridge have found out why the traditional cuff-based method often gives wrong numbers and how small changes could fix the problem.
High blood pressure, also called hypertension, is a serious health issue. It is the leading risk factor for early death around the world. It is closely linked to heart disease, strokes, and heart attacks.
Getting the correct blood pressure reading is important because missing high blood pressure can mean missed chances to treat it before it causes harm. Unfortunately, as many as 30% of people with high blood pressure may go undiagnosed due to errors in the current method.
Most people are familiar with the cuff method: a band is wrapped around your upper arm, inflated until it stops blood flow, and then slowly deflated. During deflation, a doctor listens with a stethoscope for certain tapping sounds that signal blood is flowing again.
The numbers from the cuff’s pressure gauge show your blood pressure. These two numbers are called systolic (the top number) and diastolic (the bottom number). A normal reading is 120/80.
The cuff method, also known as the auscultatory method, is considered the ‘gold standard.’ But according to researcher Kate Bassil from Cambridge, this method tends to underestimate the systolic pressure and overestimate the diastolic pressure.
The reasons for the diastolic overestimation were already known, but the systolic underestimation remained a mystery—until now.
To solve this puzzle, the research team built a model to study the physics of how blood pressure is measured. In past studies, scientists used rubber tubes to mimic arteries. However, these didn’t act like real arteries when squeezed by a cuff. The new Cambridge model used more accurate tubes that flatten and close just like real arteries do.
The team discovered that when the cuff squeezes the arm, it blocks the blood flow to the lower arm, creating very low pressure in that area. This low downstream pressure keeps the artery closed longer as the cuff deflates, which causes a delay in detecting when blood flow starts again. As a result, the systolic pressure is read as lower than it really is.
This delay in reopening the artery is a key reason for the inaccuracy. Since most doctors and nurses don’t currently adjust for this effect, it means many people with high systolic blood pressure could go undiagnosed. This new understanding might help improve how we detect and treat hypertension.
The good news is that we might not need new equipment to fix the issue. Simple changes to how blood pressure is measured—like raising the patient’s arm before taking a reading—could reduce these errors. This method could help balance the downstream pressure and make results more accurate.
If new devices are built in the future, they could also include extra information, like a person’s age, body type, or tissue details, to help adjust blood pressure readings. But even without new tools, just changing the measurement routine could make a big difference.
The Cambridge researchers now want to test their theory in real patients and are seeking partners and funding for clinical trials. They hope to work with doctors and other researchers to improve accuracy for all types of people and communities.
In summary, this study helps explain a long-standing medical mystery and offers a simple path forward. Better blood pressure readings could lead to better treatment, helping people stay healthier for longer.
If you care about blood pressure, please read studies that turmeric and vitamin D may boost blood pressure control in type 2 diabetes and scientists find link between blood pressure drugs and bowel diseases.
For more about blood pressure, please read studies about high blood pressure treatment: ARBs vs. ACE inhibitors and blood pressure response to exercise can predict future heart disease.
The study is published in PNAS Nexus.
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