Systolic hypertension, commonly known as high blood pressure (BP), affects over 4 billion adults worldwide and is the leading modifiable risk factor for cardiovascular disease—the foremost cause of death globally. Lowering elevated BP through lifestyle changes is the most effective way to reduce the risk of cardiovascular disease. However, in underserved populations, many individuals lack access to BP cuffs, and regular medical appointments, or may not even be aware of their condition. Despite this, they often possess smartphones. Now, an innovative technology utilizing a smartphone application offers a unique opportunity to alleviate the global burden of systolic hypertension, especially in underserved communities.

Researchers at the University of Pittsburgh (Pittsburgh, PA, USA) are pioneering a novel approach to BP monitoring by using smartphones people carry with them every day. Instead of creating a new medical device, the team decided to leverage the smartphones that are nearly ubiquitous, exploring how to detect BP using sensors already built into them. They utilized tools commonly found in most smartphones—such as motion-sensing accelerometers, front-facing cameras, and touch sensors—to build an Android application capable of measuring an individual's pulse pressure. To take a measurement, the user performs a hand-raising motion while holding the smartphone.

Turning a smartphone into a monitoring device proved challenging, as the team discovered through multiple iterations of app development. Since smartphones lack force-sensing tools, a crucial aspect was figuring out how to replicate the effects of a traditional blood pressure exam using only a cell phone. The team addressed this by employing a familiar force—gravity. When a person raises their hand above heart level, gravity causes a hydrostatic pressure change in the thumb. Using the phone’s accelerometer, this change can be converted into a relative pressure measurement. By combining this hand-raising motion with guided thumb maneuvers on the smartphone, the researchers were able to calculate each participant's pulse pressure. Pulse pressure is the difference between the systolic (upper) and diastolic (lower) numbers—for example, a BP measurement of 120/80 results in a pulse pressure of 40.

Although pulse pressure is not typically used in cardiovascular disease monitoring, the study revealed its significance as a metric for detecting hypertension. With individuals living in rural parts of the U.S. being 40% more likely than urban residents to develop heart disease, this technology could be crucial for providing accessible healthcare tools to communities both in the United States and around the world. Looking ahead, the team is working on further improving smartphone blood pressure monitoring to make it accessible to those who need it most. The results of the project were published in Scientific Reports, marking a promising advancement in blood pressure measurement devices for the team.

“Development of a cuffless blood pressure measurement device that does not require any external calibration is the holy grail—such a device currently does not exist,” said Sanjeev G. Shroff from the Department of Bioengineering at the University of Pittsburgh. “The research work reported in this publication is an important step in the right direction, and is also encouraging for additional work aimed at obtaining systolic, diastolic, and mean pressures.” 

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