Researchers at the University of Cambridge have identified why common cuff-based blood pressure measurements can be inaccurate and proposed ways to improve them. Their findings could help ensure better health outcomes for patients by making diagnoses more reliable.
High blood pressure is a leading risk factor for premature death, contributing to heart disease, strokes, and heart attacks. Inaccuracies in current blood pressure measurement methods mean that up to 30% of hypertension cases may go undetected.
The Cambridge team developed an experimental model that sheds light on the physical reasons behind these inaccuracies. Their study, published in PNAS Nexus, explains the mechanics of cuff-based readings and offers potential improvements without requiring new equipment.
Most people are familiar with the auscultatory method used in clinics, where a cuff is inflated around the upper arm and then slowly deflated while a clinician listens for sounds with a stethoscope. The resulting systolic (maximum) and diastolic (minimum) numbers guide diagnosis.
“The auscultatory method is the gold standard, but it overestimates diastolic pressure, while systolic pressure is underestimated,” said co-author Kate Bassil from Cambridge’s Department of Engineering. “We have a good understanding of why diastolic pressure is overestimated, but why systolic pressure is underestimated has been a bit of a mystery.”
“Pretty much every clinician knows blood pressure readings are sometimes wrong, but no one could explain why they are being underestimated — there’s a real gap in understanding,” said co-author Professor Anurag Agarwal, also from Cambridge’s Department of Engineering.
Previous research used rubber tubes that did not fully mimic how arteries behave under cuff pressure. The Cambridge researchers created a physical model using tubes that close completely when inflated by the cuff—better simulating actual human arteries.
They discovered that when the cuff cuts off blood flow to the lower arm (creating low downstream pressure), it causes arteries to stay closed longer as the cuff deflates. This delay results in underestimating true systolic blood pressure—a previously unidentified cause.
“We are currently not adjusting for this error when diagnosing or prescribing treatments, which has been estimated to lead to as many as 30% of cases of systolic hypertension being missed,” said Bassil.
To address this problem, one suggested solution involves raising the arm before taking measurements. This adjustment could create more predictable downstream pressures and make results more accurate—without needing new devices or major changes to equipment.
“You might not even need new devices, just changing how the measurement is done could make it more accurate,” said Agarwal.
If future devices are developed, they might include additional information such as age or body mass index to further tailor readings for each patient.
The researchers plan to seek funding for clinical trials involving patients and hope to collaborate with industry partners and clinicians. Their aim is to refine calibration models and confirm their findings across diverse populations so improvements can be implemented widely in clinical practice.
The project received support from the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation (UKRI). Professor Anurag Agarwal is also a Fellow at Emmanuel College, Cambridge.