Blood pressure is one of the most common measurements in healthcare, yet the standard method used—cuff-based blood pressure readings—may not be as reliable as most people think.
A new study by researchers at the University of Cambridge reveals why this method can be inaccurate and how simple changes could make it better. Their findings could help prevent missed diagnoses of high blood pressure and lead to better health outcomes.
High blood pressure, or hypertension, is a major risk factor for heart disease, stroke, and heart attacks. However, studies have shown that as many as 30% of hypertension cases could be missed due to errors in blood pressure readings. That’s a serious issue, since high blood pressure often shows no symptoms until a major health event occurs.
The standard cuff method, also known as the auscultatory method, involves inflating a cuff around the upper arm until it stops blood flow to the lower arm.
As the cuff slowly deflates, a doctor or nurse listens through a stethoscope for tapping sounds, which help determine two key measurements: systolic (the top number) and diastolic (the bottom number) pressure. An ideal reading is 120/80.
Although this method is the gold standard, it’s known to underestimate systolic pressure and overestimate diastolic pressure. Researchers have long understood why the diastolic reading is off, but the underestimation of systolic pressure has remained a mystery—until now.
The team at Cambridge built a physical model to better understand how cuff-based readings work. In earlier studies, researchers had used rubber tubes to mimic arteries.
These tubes didn’t behave like real arteries under pressure, so they didn’t show the full picture. The Cambridge team improved this model by using flat tubes that fully collapse under pressure, just like real arteries.
What they found was surprising. When the cuff cuts off blood flow to the lower arm, the pressure below the cuff becomes very low. This low downstream pressure keeps the artery closed for longer as the cuff deflates. As a result, the tapping sounds that indicate systolic pressure begin later than they should, making the reading appear lower than it truly is.
This delay in artery reopening is the likely reason systolic pressure is underestimated in cuff-based readings. And since most healthcare professionals don’t adjust for this, many patients with high systolic blood pressure could go undiagnosed.
The good news is that fixing the problem might be easier than expected. The researchers suggest that simply raising the arm before taking a reading could help create a predictable downstream pressure, making the measurement more accurate. This adjustment doesn’t require new equipment—just a change in how blood pressure is measured.
If new devices are developed, they could also be designed to take into account factors like age, body mass index (BMI), or tissue characteristics that affect downstream pressure. This would allow blood pressure readings to be tailored to individual patients for greater accuracy.
The Cambridge researchers hope to launch clinical trials to test their findings in real-world settings. They are also seeking partners to help refine their models and confirm that the same effects occur across diverse populations. Collaboration with doctors and healthcare providers will be essential for bringing these improvements into everyday practice.
This research was funded by the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation (UKRI). With a few simple adjustments, a small change in how we measure blood pressure could make a big difference in how we diagnose and treat one of the world’s most common health problems.
If you care about high blood pressure, please read studies about what to eat and to avoid for high blood pressure, and 12 foods that lower blood pressure.
For more health information, please see recent studies about the connection between potato and high blood pressure, and how to eat your way to healthy blood pressure.
The findings are published in PNAS Nexus.
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