Under Pressure?

Hypertension, commonly known as high blood pressure, is a prevalent health issue affecting large numbers of people worldwide. It occurs when the force of blood against the walls of the arteries is consistently too high, leading to long-term damage to the blood vessels and organs. Hypertension often develops gradually over time and is influenced by various factors, including lifestyle choices, genetics, and underlying medical conditions.

If left untreated or uncontrolled, hypertension can lead to severe health problems. The persistent high blood pressure puts strain on the heart, leading to an increased risk of heart disease, heart attacks, and heart failure. It can also damage the arteries, leading to atherosclerosis (hardening of the arteries), which further increases the risk of heart attacks and strokes.

Early detection and management of hypertension are crucial for minimizing the risks and complications associated with this condition. Regular blood pressure screenings are essential, especially for individuals with risk factors such as a family history of hypertension, obesity, sedentary lifestyle, smoking, excessive alcohol consumption, and certain medical conditions like diabetes. Detecting high blood pressure early allows for timely interventions such as lifestyle modifications (e.g., healthy diet, regular exercise, stress reduction), medication if necessary, and ongoing monitoring.

The prevalence of hypertension is alarmingly high and continues to rise. According to the World Health Organization, more than 1.13 billion people globally have hypertension, making it one of the most common cardiovascular diseases. It affects people of all ages, ethnicities, and socioeconomic backgrounds. The burden of hypertension is particularly significant in low- and middle-income countries where access to healthcare resources may be limited.

To make self-monitoring of blood pressure easier and more accessible, researchers at the University of California San Diego have developed a low-cost clip that can be attached to virtually any smartphone to capture accurate blood pressure measurements. Each plastic clip costs about 80 cents to produce, and at a larger scale, the team believes they could cost as little as 10 cents.

Called BPClip, the system consists of a 3D-printed plastic clip and spring-loaded mechanism, similar in appearance to a pinhole camera, that fits over the camera and flash of a smartphone. As the clip is pressed down, the smartphone’s flash turns on, which illuminates the fingertip. This projects a red circle through the clip’s pinhole to the camera. The spring allows the user to press with varying levels of force, which changes the size of the red circle picked up by the camera.

A companion app uses information received from the camera, namely the size and brightness of the red circle, to measure the pressure applied by the finger and the volume of blood in the fingertip. The app then translates these readings into systolic and diastolic blood pressure measurements.

BPClip was built with simplicity in mind. There is no need for calibration of the unit, even before the very first use by a new user. Moreover, it is not tied to a particular type of phone, or specialized sensors. Just about any commodity smartphone with a camera and flash should work fine in theory.

A small validation study with 29 participants was conducted to assess the accuracy of the technique. Measurements were taken with a traditional blood pressure cuff to obtain the ground truth values, and also using the BPClip system. A mean absolute error of 8.7 and 5.5 for systolic and diastolic blood pressure was observed, respectively. There is a bit of room for improvement, but these early results are very encouraging.

The researchers hope to democratize blood pressure monitoring by converting billions of inexpensive smartphones into low-cost monitors. Given the accuracy, simplicity, and low fabrication cost of BPClip, that goal may be realized in the near future.