A contactless method of monitoring vital signs

27th April 2023
Harry Fowle

The team at Analog Devices have been making exciting progress towards its new device which will hopefully one day allow for a completely contactless method of monitoring vital signs within the healthcare sector.

With traditional methods of vital sign monitoring remaining invasive and uncomfortable for many, the need for modernised methods is ever-growing. This is the gap that Analog Devices aims to fill with its small devices that can detect and measure heart and breathing rates through the mattress a patient is staying on. To learn more, Electronic Specifier spoke to Dr. Kate Fischl, Principal Research Scientist at Analog Devices, who is currently working on the development of the device.

How does it work?

The product itself is a small 3D-printed box, no bigger than the palm of your hand, so how does it manage to accomplish such feats of measurement? Within the box is an accelerometer, specifically the ADXL 355, which Dr. Fischl describes as “a sensor which measures changes in speed or changes in acceleration,” but on a much more sensitive and intricate scale. This accelerometer is what picks up heartbeats and breathing rates for measurement and display.

“When your heart is pumping blood to your body, after the heart pumps, there’s a recoil force. That small mechanical reverberation can be picked up by the system. I like to think of it as, as your heart moves, it’s moving the mattress in the bed and then the sensor can detect that change in movement,” explains Dr. Fischl.

“And then thinking about respiration rate, as you breathe in and out, your lungs are filled with air and that kind of causes your body to tilt, which causes the mattress to tilt, and that changes the position of the accelerometer in the bed. That’s the signal we are able to process to then get your respiration rate,” continues Dr. Fischl.

Whilst this is already incredible work, what is stopping the device from simply making errors, or picking up background noise? This is where the algorithm side of the device comes into play, which does an incredible amount of technical signal processing to find the correct low noise frequencies and subtle movement data to display accurate measurements, utilising AI to optimise the process.

“We’re also calculating heart rate variability from the heart rate,” added Dr. Fischl, which is a bonus that can have long-term health monitoring applications.

“We saw that we were getting above 90% accuracy on the respiration rate, although the heart rate accuracy still needs fine-tuning.”

Tests like these have shown the team at Analog Devices that what they are developing has some very promising future capabilities once fine-tuned. Dr. Fischl made clear that future testing was required to fully understand the device’s current flaws and areas of improvement, as well as to eliminate any biases that may be present within its algorithms. “This is certainly the first step, taking it out of the research department and having someone else validate its ability,” says Dr. Fischl.

The applications of contactless vital monitoring

Once fully developed and working, Analog Devices hopes that its non-contact vital monitoring device will see a wide array of applications in the healthcare sector.

“I think one clear application area that we’re targeting from the get-go is thinking about outside of the intensive care unit in hospitals,” says Dr. Fischl. In essence, putting these devices in the beds of non-critical condition patients offers a far less intrusive way to measure vital signs accurately and efficiently.

“There are also other areas that I think have great potential applications, such as in elder care,” continued Dr. Fischl. This type of device, as previously mentioned would give a much less intrusive way to complete both short- and long-term vital monitoring, this can offer valuable information for sudden changes to health, as well as for gradual changes such as those seen in neurodegenerative diseases.

On the other side of the age spectrum, Dr. Fischl also hopes that the device could be a great way to monitor the vitals of babies as they sleep, utilising its non-intrusive non-contact method to minimise discomfort for the baby. This could, similarly to in the care of the elderly, aid in spotting long-term problems as well as alerting parents to short-term emergency scenarios.

Finally, Dr. Fischl touched on potential at-home use cases, for self-monitoring sleep quality to detect things such as sleep apnoea, however, this would only be considered once accuracy was no longer of concern.

Not quite there yet, but soon!

Overall, despite early concerns, the problems that have arisen are all things that can be readily addressed given further development and Dr. Fischl is optimistic about the future of the product. “Now that we’ve shown, with the first clinical trial, that we do have accuracy and a baseline, we get to start thinking about those challenges, which is just a really fun place to be,” observes Dr. Fischl.

Maybe in the future, you might find yourself stepping into a hospital in which every bed has a contactless way to monitor the vitals of its patients.

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