Blood pressure checks are one of the most common medical tests in the world. Millions of people have their blood pressure measured every day during doctor visits, hospital appointments, and routine health screenings.
Doctors rely on these readings to identify people at risk of heart disease, stroke, and other serious health problems. But researchers from the University of Cambridge now say that the traditional method used to measure blood pressure may not be as accurate as many people believe.
Their new study explains why the standard cuff-based method can sometimes give incorrect readings and suggests that simple changes could improve accuracy without needing expensive new equipment.
High blood pressure, also known as hypertension, is one of the biggest causes of early death worldwide. It can quietly damage blood vessels and organs for years without causing obvious symptoms.
Because of this, hypertension is often called a “silent killer.” If left untreated, it can increase the risk of heart attacks, strokes, kidney disease, heart failure, and other dangerous conditions.
Finding high blood pressure early is very important because treatment can greatly reduce these risks. However, researchers estimate that up to 30% of people with high blood pressure may not be diagnosed correctly because of problems with current blood pressure measurement methods.
Most people are familiar with the standard blood pressure test. A cuff is wrapped tightly around the upper arm and inflated until blood flow through the artery is temporarily blocked.
The cuff is then slowly deflated while a doctor or nurse listens with a stethoscope for tapping sounds created by blood beginning to flow again through the artery.
The pressure reading when these sounds first appear is called the systolic blood pressure, which is the top number in a blood pressure reading.
The pressure reading when the sounds disappear is called the diastolic blood pressure, which is the bottom number. A normal blood pressure reading is usually considered around 120/80.
This traditional technique is known as the auscultatory method and has long been considered the “gold standard” for blood pressure measurement. However, according to Cambridge researcher Kate Bassil, the method often underestimates systolic pressure while overestimating diastolic pressure.
Scientists already understood some of the reasons why diastolic pressure readings could be too high. But until now, the reason why systolic pressure readings were often too low remained unclear.
To investigate the problem, the Cambridge research team built a detailed physical model to study exactly what happens inside the arm during a blood pressure test. Earlier research had used rubber tubes to copy the behavior of arteries, but those models did not behave like real human arteries when squeezed by a blood pressure cuff.
The new model used specially designed tubes that flatten and close much more like actual arteries inside the body. This allowed the researchers to better understand how pressure changes inside the arm during the test.
The scientists discovered that when the cuff squeezes the upper arm, it blocks blood flow to the lower part of the arm. This creates unusually low pressure downstream from the cuff. Because of this low pressure, the artery stays closed for longer than expected as the cuff slowly deflates.
As a result, there is a delay before blood flow starts again and the tapping sounds become detectable through the stethoscope. Since the artery reopens later than it should, the systolic pressure reading appears lower than the person’s true blood pressure.
This delayed reopening of the artery may explain why many people with high systolic blood pressure are not properly diagnosed. Since systolic pressure is strongly linked to the risk of heart disease and stroke, underestimating it could mean missing important opportunities for treatment.
The researchers say the encouraging news is that fixing the problem may not require completely new machines or expensive medical devices. Simple adjustments to the way blood pressure is measured could help reduce the error.
One possible solution involves raising the patient’s arm before taking the measurement. According to the researchers, this could help balance the pressure in the lower part of the arm and reduce the delay in reopening the artery.
By changing the measurement process slightly, doctors and nurses may be able to obtain more accurate blood pressure readings.
The findings may also help improve future blood pressure devices. Researchers suggest that newer systems could include additional information such as age, body type, tissue characteristics, or artery stiffness to make readings more personalized and accurate.
However, even without advanced technology, the study suggests that small changes in routine medical practice could already make a meaningful difference for many patients.
The Cambridge researchers now hope to test their findings in real clinical settings involving patients from different age groups and backgrounds. They are currently looking for collaborators and funding to support larger clinical trials.
The researchers believe that improving blood pressure accuracy could have a major public health impact. Since high blood pressure affects hundreds of millions of people worldwide, even small improvements in diagnosis could help many more people receive treatment earlier and avoid life-threatening complications.
The study also highlights how even long-established medical methods may still contain hidden problems that science can improve over time. Blood pressure cuffs have been used for more than a century, yet researchers are still discovering new details about how the body and the equipment interact during testing.
If you care about blood pressure, please read studies about unhealthy habits that could increase high blood pressure risk, and people with severe high blood pressure should reduce coffee intake.
For more information about blood pressure, please see recent studies that early time-restricted eating could help improve blood pressure, and results showing plant-based foods could benefit people with high blood pressure.
The study was published in the scientific journal PNAS Nexus.
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