Far more than just a communication device and a place to play endless games of solitaire, the smartphone has turned our lives upside down since it was introduced. It is an instant gateway, offering access from wherever you are to music, email, photos and videos, games, all forms of social media, and more memes than you really need about Grumpy Cat and the latest political catastrophe.
But innovative people have also been adding new apps and 3D printed modifications to their smartphones, for the purposes of making healthcare more easily accessible. The mobile devices have been used to detect and diagnose a variety of diseases, and researchers in Australia developed a 3D printable clip-on that turns a smartphone into a functional microscope, which could help determine water quality and analyse blood samples for parasites.
A collaborative team of researchers from Michigan State University, the University of Maryland, and Chonnam National University in South Korea recently used 3D printing technology to modify a smartphone to help detect high blood pressure (BP), before it leads to a stroke or heart disease.
We’ve all likely been to a doctor’s office and had our blood pressure measured with one of those inflatable arm cuffs. While the cuff presses down on the brachial artery in your arm, a device records the effect of this compression on your blood flow.
But the research team’s new 3D printed smartphone modification can actually measure BP right from your finger – no arm cuff required. This could give medical professionals a more accessible way to assess the risk of patients for stroke and heart attack, particularly in developing countries where smartphones are more commonplace for residents than access to arm cuff-based devices.
Users simply place their finger on an optical pressure sensor located in a prototype case for a smartphone. Then, a chart displayed on the phone instructs the user to gradually increase the amount of applied force they’re exerting. At the same time, a separate sensor illuminates their finger and detects any changes in how the light is absorbed to measure their blood pressure.
The researchers published a paper on their findings, titled “Smartphone-based blood pressure monitoring via the oscillometric finger-pressing method,” in the Science Translational Medicine journal; co-authors include Anand Chandrasekhar, Chang-Sei Kim, Mohammed Naji, Keerthana Natarajan, Jin-Oh Hahn, and Ramakrishna Mukkamala.
The abstract reads, “High blood pressure (BP) is a major cardiovascular risk factor that is treatable, yet hypertension awareness and control rates are low. Ubiquitous BP monitoring technology could improve hypertension management, but existing devices require an inflatable cuff and are not compatible with such anytime, anywhere measurement of BP. We extended the oscillometric principle, which is used by most automatic cuff devices, to develop a cuff-less BP monitoring device using a smartphone. As the user presses her/his finger against the smartphone, the external pressure of the underlying artery is steadily increased while the phone measures the applied pressure and resulting variable-amplitude blood volume oscillations. A smartphone application provides visual feedback to guide the amount of pressure applied over time via the finger pressing and computes systolic and diastolic BP from the measurements. We prospectively tested the smartphone-based device for real-time BP monitoring in human subjects to evaluate usability (n = 30) and accuracy against a standard automatic cuff-based device (n = 32). We likewise tested a finger cuff device, which uses the volume-clamp method of BP detection. About 90% of the users learned the finger actuation required by the smartphone-based device after one or two practice trials. The device yielded bias and precision errors of 3.3 and 8.8 mmHg for systolic BP and −5.6 and 7.7 mmHg for diastolic BP over a 40 to 50 mmHg range of BP. These errors were comparable to the finger cuff device. Cuff-less and calibration-free monitoring of systolic and diastolic BP may be feasible via a smartphone.”
The research team tested out their 3D printed prototype smartphone case on 30 people, and reported that the majority quickly learned how to use it – it took about 90% of the participants less than three attempts to correctly position their finger on the sensor and get consistent readings.
Early results from this trial were published in the paper, and showed that the readings the device provided were not as precise as those resulting from a standard arm cuff; the researchers said that this accuracy could be improved by taking multiple measurements over a period of time. The paper also showed that the BP readings were similar when comparing the results from an arm cuff, the 3D printed prototype, and a finger cuff device.
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