Cuff-based blood pressure monitors (the 'gold standard') can underestimate systolic pressure, meaning many cases of high blood pressure may go undetected.
A new physical model using realistic artery behavior reveals that low downstream pressure delays artery reopening during measurement, causing the error.
Straightforward tweaks, such as raising the arm before measuring, have potential to improve accuracy — without needing new or expensive devices.
You’ve probably had your blood pressure taken with a cuff around your arm — inflate, listen, repeat. It’s the go-to method doctors trust, known as the auscultatory technique.
But a surprising discovery from researchers at the University of Cambridge shows this routine approach may miss up to 30% of high-blood-pressure cases. That’s not just a statistic — it’s a wake-up call for more accurate health checks.
“The auscultatory method is the gold standard, but it overestimates diastolic pressure, while systolic pressure is underestimated,” co-author Kate Bassil from Cambridge’s Department of Engineering said in a news release.
“We have a good understanding of why diastolic pressure is overestimated, but why systolic pressure is underestimated has been a bit of a mystery.”
How did the researchers figure this out?
Scientists set out to better understand why readings are off — specifically, why they tend to underestimate systolic pressure and overestimate diastolic pressure. Earlier study models used simple rubber tubes, which didn’t mimic how real arteries collapse under cuff pressure. That flaw masked a key issue.
The researchers built a simplified physical model that better replicated real artery behavior — specifically tubes that flatten when deflated and fully close when the cuff is inflated.
This setup allowed them to isolate what happens below the cuff. They discovered that once blood flow is cut off, pressure downstream drops very low — this keeps the artery closed for longer as the cuff deflates, thus delaying its reopening and skewing the measurement.
Results: What does that mean and how do we fix it?
Firstly, this newfound mechanism likely explains why standard cuff readings miss up to 30% of cases of systolic hypertension.
But there’s a bright side: the fix could be simple. For instance, raising the arm before measurement might create a more predictable downstream pressure, reducing the underestimation.
“You might not even need new devices, just changing how the measurement is done could make it more accurate,” researcher Anurag Agarwal said in the news release.
Looking ahead, if new devices are developed, they could incorporate factors like a person’s age, BMI, or tissue traits to account for downstream pressure. But for now, small protocol tweaks may already make a real difference.