The Healthy Pi — a Medical HAT for the Raspberry Pi

The fallout from the smartphone war has left us with many gifts, as Chris Anderson puts it “…when giants battle we all win.” The technology…

The fallout from the smartphone war has left us with many gifts, as Chris Anderson puts it “…when giants battle we all win.” The technology dividend from the war is readily evident when you start to look around. Sensors such as accelerometers, gyroscopes, magnetometers, and even cameras, are cheap and readily available. Looking at the hardware available to us as makers, there is a sensor available to measure just about anything you might want to measure. But only just about.

What isn’t as readily available are the more exotic sensors, gas and particulate sensors for instance, or medical sensors. Enter the HealthyPi v3 from ProtoCentral, raising now on Crowd Supply.

The HealthyPi V3 HAT for the Raspberry Pi was an entrant into this year’s Hackaday Prize in the Internet of (useful Things) IOT round, although not picked as one of the final twenty projects in the round.

The board can provide your electrocardiogram (ECG), showing the electrical activity of the heart which translates to measure of your heart function, your photoplethysmography (PPG), a measure of the blood flow from the periphery, and can also provide heart rate, and blood oxygen saturation levels (SpO2), and respiration rate. It is a full featured vitals signs monitor which can display data locally, or send it via MQTT up into the cloud.

It also looks to have excellent open source credentials, with hardware schematics, layout, and bill of materials all being made available on GitHub, alongside a fully open source Arduino firmware, and Processing-based GUI display software. However, I worry.

The HealthyPi lacks any sort of certification, such as FDA approval, so it can’t be used in medical facilities. In most western countries it can’t even really be sold as a medical device, or on its medical and diagnostic abilities.

One of the major complaints I have about a lot of sensors sold into the maker market is that they’re uncalibrated. Most of the time this doesn’t matter that much. But, while things like solid state temperature and MEMS based pressure and humidity sensors are usually pretty robust, other sensors — especially particulate or gas sensors — sometimes require periodic calibration, or even calibration before each and every use, to be even vaguely accurate. Calibration that they usually don’t get outside of a laboratory setting because most people don’t know it’s needed. Which means that measurements they take may have a larger than normal random error, but in a lot of cases also dramatic and worrying systematic errors.

Which always makes me somewhat wary about open hardware medical sensors targeted at makers. They’re only going to be as good as their calibration.

However this isn’t the only open medical device that the manufacturer produces, and while there isn’t any hard data comparing the the HealthyPi v3 to a standard—and much more expensive—professional vitals monitor I’m hopeful that Protocentral might provide some. It would be helpful to see hard data on how the board compares to a ‘real’ vitals monitor, alongside suggestions for initial calibration, and how to check and maintain that calibration during use.

If you’re interested in the HealthyPi v3, it’s currently available on Crowd Supply with pledge levels starting at $195 and free worldwide shipping.

Alasdair Allan
Scientist, author, hacker, maker, and journalist. Building, breaking, and writing. For hire. You can reach me at 📫 alasdair@babilim.co.uk.
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