Researchers have developed a simple, inexpensive clip that uses a smartphone camera and flash to monitor blood pressure on the user’s fingertip. Developed by researchers at the University of California (UC) San Diego in the US, the clip works with a custom smartphone app and currently costs about 80 cents (Rs. 5.6) to make.
The researchers estimate that the cost could be as low as 10 cents (0.7 rupees) per piece if produced on a large scale. The technology, described in the journal Scientific Reports, could help make regular blood pressure monitoring easy, affordable and accessible to people in under-resourced communities, they said.
According to the researchers, this could benefit older adults and pregnant women, for example in managing conditions such as hypertension.
“We have created a low-cost solution to reduce the barrier of blood pressure monitoring,” said study first author Yinan Xuan, a doctoral student at UC San Diego. Because of their low cost, these clips could be given to anyone who needs them but can’t go to the clinic regularly,” said study lead author Edward Wang, a professor at UC San Diego and director of the Digital Health Lab.
Another key advantage of the clip is that it does not need to be calibrated to the cuff, the researchers said. “This is what sets our device apart from other blood pressure monitors,” Wang said.
Other cuffless systems being developed for smartwatches and smartphones, he explained, require obtaining a separate set of cuff measurements in order to tune their models to match those measurements.
“Our system is calibration-free, which means you can use our device without touching another blood pressure monitor to get a reliable blood pressure reading,” Wang said.
To measure blood pressure, the user simply presses the clip with a fingertip. A custom smartphone app guides the user on how hard and how long to press during the measurement.
The Clip is a 3D-printed plastic attachment that fits over a smartphone’s camera and flash. It features an optical design similar to that of a pinhole chamber. When the user presses the clip, the smartphone’s flash lights up the fingertip.
This light is then projected through a pinhole-sized channel into the camera as an image of a red circle. A spring inside the clip allows the user to press with varying levels of force. The harder the user presses, the bigger the red circle appears on the camera.
The smartphone app extracts two main pieces of information from the red circle. By looking at the size of the circle, the app can measure the amount of pressure the user exerts with their fingertip. By looking at the brightness of the circle, the app can measure the volume of blood flowing in and out of the fingertip.
The algorithm converts this information into systolic and diastolic blood pressure values. The researchers tested the clip on 24 volunteers from the UC San Diego Medical Center. The results were comparable to those obtained with a blood pressure cuff.
“Properly donning a standard blood pressure cuff can be uncomfortable, and this solution has the potential to make it easier for older adults to monitor blood pressure,” said study co-author Alison Moore of the UC San Diego School of Medicine.
Written by: Vaishali Verma
