High blood pressure (or hypertension) increases the risk of health problems such as heart or kidney failure, but goes undiagnosed in millions of people. A newly developed Android phone app can remotely assess the pressure in a person’s arteries as the heart contracts, providing potentially life-saving data about a person’s health without the need for special equipment.

Developed by a team led by researchers at the University of Pittsburgh, the app works by taking various readings from the accelerometer, camera and touch sensors built into modern smartphones.

One day, people will be able to use the phone in their pockets instead of going to the doctor or using a special device, making this innovation especially important for the population with limited access to healthcare. “In underserved populations, many people don’t have access to blood pressure cuffs, don’t have regular doctor appointments, or have smartphones without even knowing it’s a problem,” says University of Pittsburgh biomedical engineer Ramakrishna Mukkamala.

Blood pressure is usually measured using a tongue-in-cheek device called a sphygmomanometer. The inflated cuff compresses the main artery in the arm, squeezing it before slowly releasing flow again.

With each heartbeat, the pressure changes between contraction – systolic pressure – and relaxation – diastolic pressure. In a blood pressure reading, systolic pressure is represented by the higher number and diastolic pressure is represented by the lower number.

Some digital devices can automatically report the change, but doctors can also use a stethoscope to listen to the pulse and estimate the pressure difference and record it in millimeters of mercury or mmHg. Systolic index is above 130 mm Hg. is often interpreted as a reason to continue watching.

Smartphones cannot apply pressure to stop and restore blood flow like a traditional blood pressure cuff. As an alternative approach, the app uses the force of gravity and the force of finger pressure on the phone’s touch screen to determine pulse pressure.

What makes the app smart is that it forces users to reposition their hands to change blood flow and tap the phone’s screen in multiple directions to get accurate pulse pressure measurements.

“Due to gravity, when you lift your hands over your heart, there’s a change in hydrostatic pressure in your thumb, and with the phone’s accelerometer, you can translate that into a relative pressure change,” says biomedical engineer Vishaal Dhamotaran of the University of Pittsburgh.

When tested on 24 people and cross-referenced with a larger database, the app’s method detected pulse pressure at a fairly accurate level of around 8 mmHg. As development continues, the accuracy level of the application is likely to increase further.

The researchers admit they need to work on a “mindset change” about using pulse pressure as a blood pressure indicator, but this is the best solution we’ve seen to get this important value from a regular smartphone.

“Developing a cuffless blood pressure device that does not require any external calibration is the holy grail; there is currently no such device,” says Sanjiv Shroff, a biomedical engineer at the University of Pittsburgh.

“The research reported in this publication is an important step in the right direction.” The study was published on: Scientific Reports.