Taking your blood pressure with a cuff is something millions of people do every day. But a new study shows this common method may not always give the right results—and that simple changes could make it much better.
Researchers from the University of Cambridge have discovered why these readings can be off and how to improve them without needing new equipment.
High blood pressure, or hypertension, is one of the biggest health risks worldwide. It increases the chances of heart attacks, strokes, and early death.
But surprisingly, the tool we use most to measure it—the arm cuff—can give wrong numbers. In fact, up to 30% of people with high blood pressure might not be diagnosed properly because of this inaccuracy.
The method used by most doctors is called the auscultatory method. A cuff is placed on your upper arm and inflated until it stops blood from flowing to your lower arm. Then the cuff slowly deflates while the doctor listens for certain sounds with a stethoscope.
These sounds help determine the two blood pressure numbers: systolic (the higher number) and diastolic (the lower number). A typical healthy reading is 120/80.
For years, doctors have noticed that this method often underestimates the systolic pressure and overestimates the diastolic pressure. But no one was sure why. The Cambridge team decided to investigate by building a physical model that mimics what happens inside the arm during a blood pressure test.
They discovered that when the cuff inflates and blocks blood flow, the pressure in the lower arm drops very low. This low pressure makes the artery stay closed longer than it should as the cuff deflates.
As a result, the point where the artery opens and blood starts flowing again (which is used to determine systolic pressure) is delayed. This delay causes the device to show a lower systolic pressure than the real one.
Earlier models used rubber tubes that didn’t behave like real arteries. The Cambridge researchers used better materials that flattened when empty and fully closed under pressure—closer to how real arteries work. This allowed them to see the true effects of low downstream pressure and how it caused inaccurate readings.
The good news is that fixing the problem doesn’t require new machines. One simple solution is to raise the arm before taking the measurement. This may help create a more predictable pressure in the lower arm and reduce the error. Just changing how the test is done—not the device itself—could make a big difference.
If new devices are developed, they might use extra information, like a person’s age, weight, or body type, to adjust readings more accurately. This would allow for more personalized and reliable results.
The researchers are now looking to test their ideas in real-life settings with patients. They hope to work with doctors and industry partners to develop better models and test the methods on people from different backgrounds. Their goal is to improve blood pressure readings for everyone.
In summary, this study gives us a better understanding of why common blood pressure tests can give the wrong results, especially for the top number (systolic pressure). By learning how low pressure in the lower arm affects the timing of blood flow, we now have a way to fix the problem.
With some simple changes to how we measure blood pressure, we could help more people get the correct diagnosis and treatment—leading to better health outcomes.
If you care about blood pressure, please read studies about blood pressure drug that may increase risk of sudden cardiac arrest, and these teas could help reduce high blood pressure.
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