Smartphone App, Device Shown to Measure Blood Pressure

Smartphone blood pressure system (Michigan State University)

9 March 2018. A smartphone-based system and app were shown in a pilot study with human subjects to measure a person’s blood pressure with about the same accuracy as some cuff devices normally used to gauge blood pressure. A team from Michigan State University in East Lansing and University of Maryland in College Park describe the system and test results in the 7 March issue of the journal Science Translational Medicine (paid subscription required).

The researchers led by Michigan State biomedical engineering professor Ramakrishna Mukkamala are seeking more convenient methods for measuring blood pressure. Hypertension, or high blood pressure, is a common condition affecting 1 in 3 adults in the U.S., or about 75 million people, according to Centers for Disease Control and Prevention. But barely more than half of people with the condition (54%) have their blood pressure under control, despite hypertension increasing the risk for heart disease and stroke.

Hypertension is a treatable condition, and as part of treatment, CDC recommends regularly checking blood pressure, but few people have the specialized equipment in their homes, usually inflatable arm cuffs. Mukkamala and colleagues developed their system as a way to make blood pressure measurement more readily available, without people needing to acquire a specialized device. Instead, the team designed their solution using the smartphone, the ubiquitous information technology in the hands and pockets of increasing numbers of people worldwide.

The system, designed by Michigan State doctoral candidate and first author Anand Chandrasekhar, uses the same basic principle as cuff-style blood pressure devices. These arm-cuff devices measure blood volume oscillations in the brachial artery, after the cuff is fully inflated, and then as the cuff is gradually deflated. The researchers’ device also measures blood volume oscillations, but with a different artery: the transverse palmar arch artery in the fingers.

The system combines circuitry built into a case for the smartphone, with a companion app. The back of the case has force and optical sensors for measuring blood volume oscillations that users press with their fingers in slowly increasing pressure. Readings from the sensors are transmitted to the app, which displays the measurements on a real-time chart, providing the person’s blood pressure as well as visual feedback on proper use of the device.

A critical milestone in developing the system, and focus of the team’s first set of tests with 30 volunteers, was whether novice users could understand the system and work it properly. “A key point was to see if users could properly apply the finger pressure over time,” says Mukkamala in a university statement, “which lasts as long as an arm-cuff measurement. We were pleased to see that 90 percent of the people trying it were able to do it easily after just one or two practice tries.”

The researchers then recruited 32 volunteers to test a prototype system against cuff devices. Participants were asked to take 2 to 4 blood pressure measurements with the smartphone system, as well as with a standard arm cuff, and a finger cuff, which inflates like an arm cuff, but measures blood pressure with the transverse palmar arch artery. The results show the smartphone system measures blood pressure with bias and precision error rates close to acceptable ranges dictated by medical instrumentation standards. The findings also show those error ranges were similar to rates returned by finger cuff devices.

The authors conclude that the smartphone blood pressure system has promise, but still needs work. The device, say the authors, can be improved with additional sensors, more versatile algorithms, and software improvements to provide warnings if blood pressure reaches dangerous levels. Michigan State and University of Maryland applied for a patent on the finger-pressure technology, with a company, Digitouch Health LLC, already licensing its rights.

The following video tells more about the system.

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