Ten-cent BPClip may soon let smartphones check blood pressure
While it's very important for some people to monitor their blood pressure, individuals living in remote or impoverished regions may not have access to an arm-cuff-equipped clinic. A simple and inexpensive new device could help, as it works with the patient's own smartphone.
Known as the BPClip, the 3D-printed plastic gadget is being developed by a team of scientists at the University of California - San Diego. It presently costs about 80 cents per unit to make, although that figure could reportedly drop as low as 10 cents once it's being manufactured on a commercial scale.
The BPClip simply gets clipped onto one corner of the user's smartphone, so that a tiny hole in the device sits over the phone's camera lens, and a light guide in it covers the phone's flash.
Instructed by an accompanying app, the user then presses a fingertip down onto the hole – a spring in the clip provides resistance, allowing them to take multiple readings using different amounts of force.
For each reading, the camera takes a photo of the flash-lit underside of the fingertip, looking through the hole. Because the hole is so small, each image just takes the form of a red dot. The diameter of that dot increases as more pressure is applied, while the brightness of the red color varies with the volume of blood being pumped in and out of the finger.
Therefore, by analyzing the size and brightness of the dot in the different photos, an algorithm in the app is able to determine and display the user's current systolic and diastolic blood pressure. In lab tests performed on 24 volunteers, these measurements were approximately the same as those obtained using a traditional arm cuff.
And importantly, while we have heard about other smartphone-connected blood-pressure-monitoring devices, most of those have initially needed to be calibrated using an arm cuff as reference. By contrast, the BPClip requires no such calibration, so patients can commence using it when and wherever they wish without ever accessing a cuff.
The scientists are now working on increasing the device's compatibility with different skin colors and different types of smartphones, and on making it easier to use. It is being commercialized through UC San Diego spinoff company Billion Labs Inc.
"Because of their low cost, these clips could be handed out to anyone who needs them but cannot go to a clinic regularly," said Prof. Edward Wang, senior author of a paper on the research. "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."
The paper was recently published in the journal Scientific Reports.