Contactless sensors detect developing pressure ulcers

The contactless system, developed by Irish researchers, focuses on detecting tissue blood flow — or perfusion — which when restricted can lead to ulcers.

Currently there are methods to detect pressure at the interface between skin and supporting surfaces, but this only provides a proxy for perfusion.

Perfusion itself can be measured using bulky apparatus such as ultrasound, plethysmography or electromagnetic flowmetry, but these too have drawbacks — as project collaborator Dr Sonja Hermann of Trinity College Dublin explained.

‘You can only measure by lifting the limb or the part you’re interested in off the surface, so there’s no really direct measurement of what’s going on when people are lying or sitting down.

‘Also, by using these methods — for example, with the ultrasound head — you actually apply pressure onto the skin and by doing so you’re changing the environment you’re trying to measure.’

The team’s solution was to use a commercially available thin-film ferroelectret sensor — a material that shows similar behaviour to piezoceramics by generating a current upon mechanic stress.

They were able to adapt these sensors to capture a ballistocardiogram (BCG) profile, which describes the recoil acceleration in blood vessels from flow and thus tissue perfusion.

Crucially, the sensors can be placed underneath mattresses, wheelchairs or any supporting surface, allowing true in situ monitoring. The device can then be coupled to a laptop where the data is fed through bespoke algorithms and interpreted by a clinician.

Hermann said the information could potentially be used in conjunction with the pressure-release mattresses that some hospitals now use. These are essentially air-filled beds that shift pressure in cycles so one body part is never under pressure for too long.

‘It works okay, but they [nurses] don’t really know when to initiate these cycles and how to actually manipulate them according to the patients’ data, there might only be two or three settings.

’It’s a very rough estimate that has to fit all people, and every patient has a different risk of pressure ulcers in different areas of the body.’

In the future though, the data from the BCG sensors could feed into an entirely automated pressure-relief system, in a ‘closed-loop’ fashion.

Hermann and colleagues are now performing clinical trials in order to gain a better understanding of how different illnesses effect perfusion, with funding from the Irish Research Council for Science, Engineering and Technology (TRCSET) and Center for Excellence in Universal Design.

Given the extremely high costs of treating advanced-stage pressure ulcers, the team hopes to be able to commercialise its preventative technology and is looking for potential backers.