Understanding the Limitations of Cuff-Based Blood Pressure Measurements and How Improvements Can Enhance Accuracy

High blood pressure, or hypertension, remains the leading risk factor for premature death worldwide, contributing significantly to heart disease, strokes, and heart attacks. Despite the widespread use of cuff-based blood pressure measurements in clinical practice, research indicates that these readings can often be inaccurate, potentially missing up to 30% of hypertension cases.

A recent study by researchers at the University of Cambridge has shed light on the physics behind these inaccuracies. Traditional cuff-based methods, known as auscultatory measurements, involve inflating a cuff around the upper arm to stop blood flow temporarily, then slowly deflating it while listening for specific sounds through a stethoscope. Blood pressure readings are derived from the pressure gauges attached to the cuff, providing two numbers: systolic (maximum pressure) and diastolic (minimum pressure). The ideal blood pressure level is considered to be around 120/80 mmHg.

However, clinicians and researchers have long noted that this method tends to overestimate diastolic pressure and underestimate systolic pressure. While the overestimation of diastolic pressure has been well understood, the reason for systolic underestimation remained unclear.

Through their experiments, the Cambridge team constructed a physical model simulating arteries and blood flow. They discovered that when the cuff inflates and blood flow is stopped, the downstream pressure below the cuff becomes very low. This low downstream pressure causes the artery to stay closed longer while the cuff deflates, delaying its reopening. This delay results in an underestimation of the true systolic blood pressure, a phenomenon caused by a physical mechanism previously not fully recognized.

The study suggests that many inaccuracies in blood pressure readings are due to this effect, leading to the potential underdiagnosis of hypertension. Importantly, their findings show that simple changes in measurement protocols could significantly improve accuracy. For example, elevating the arm before measurement could alter downstream pressure and reduce underestimation, without the need for new devices.

Moreover, future blood pressure monitoring technologies could incorporate additional parameters such as age, BMI, or tissue characteristics to better account for individual differences and improve measurement precision. The researchers plan to conduct clinical trials to validate these findings and work with industry and medical professionals to refine measurement protocols.

In summary, understanding and addressing the physical dynamics affecting cuff-based blood pressure readings can lead to more accurate diagnoses and better health outcomes for patients. Small protocol adjustments could drastically reduce the number of missed hypertension cases, ultimately saving lives.

Source: https://medicalxpress.com/news/2025-08-common-cuff-based-blood-pressure.html