Researchers have developed a simple, low-cost clip that uses a smartphone's camera and flash to monitor blood pressure at the fingertip.
Home monitoring is especially important for people over 50 with high blood pressure, which is a significant risk factor for cardiovascular disease and stroke.
The researchers, describing the device Monday in Scientific Reports, said they sought to make regular blood pressure monitoring easier, more affordable, and accessible to more people.
They developed a 3D-printed plastic clip attachment that fits over a smartphone’s camera and flash. To measure blood pressure, the user presses the clip with a fingertip, causing the smartphone’s flash to light up. The clip works with a custom smartphone app that provides guidance on how long and hard to press during measurement. A spring inside the clip allows users to press with different levels of force. The light from the flash is projected through a pinhole to the camera as an image of a red circle. The harder the user presses, the bigger the red circle appears on the camera.
From the size of the red circle, the smartphone app can measure the amount of pressure that the user’s fingertip applies, and from the brightness of the circle, the app can measure the volume of blood going in and out of the fingertip. An algorithm converts this information into systolic and diastolic blood pressure readings.
The researchers tested a prototype of the clip on 24 volunteers from the University of California (UC) San Diego Medical Center. The readings were found to be comparable to those taken by a blood pressure cuff. Since standard blood pressure cuffs may be challenging to put on correctly — especially for older adults — the clip may make self-monitoring easier. The researchers say it could also help pregnant women and others manage conditions including hypertension.
The clip costs about 80¢ to make. However, costs could decline to as little as 10¢ apiece when manufactured at scale, according to the researchers estimates. Furthermore, the clip does not need to be calibrated to any other blood pressure monitor to get a reliable blood pressure reading, which distinguishes it from other cuffless monitors.
While the team has only implemented this system on a single smartphone model, it expects the design to work on other phone models. Next steps include making the technology more user friendly for older adults, testing its accuracy across different skin tones, and creating a more universal design.
“Because of their low cost, these clips could be handed out to anyone who needs them but cannot go to a clinic regularly,” senior author Edward Wang, electrical and computer engineering professor at UC San Diego, said in a statement. “A blood pressure monitoring clip could be given to you at your checkup, much like how you get a pack of floss and toothbrush at your dental visit.” Wang is CEO of Billion Labs, which he co-founded with co-author Colin Barry to commercialize the technology.