Matters of the heart

VitalSens, a patch-based wireless device developed by Ulster University spin-out Sensor Technology + Devices (ST+D), transmits information about ECG, body temperature, respiration rate and SPO2 (the percentage of oxygen saturation in blood) regardless of where the patient is located.

It is now on trial at the Royal Victoria Hospital, Belfast in a £410,000 project funded by the Wellcome Trust.

Worn on the body, the two-part device is made up of a disposable adhesive patch that contains electrodes and a reusable wireless device that clips onto the patch magnetically.

Information about the patient’s vital signs can then be transmitted to a doctor via a hospital’s wireless communications system from distance sof up to 10m. Once the patient is discharged, a small, portable handset can pick up signals from the patch via GPRS and transmit data back to a doctor’s PC using wireless internet.

‘The patch under test will carry out two-lead and three-lead ECG, compared with the current model that only does single-lead ECG,’ said Prof Jim McLaughlin, an executive director at ST+D. ‘We’re building an SPO2 sensor into it and we’ll also measure respiration with an impedance algorithm.’

Similar devices are already on the market, a fact that McLaughlin readily acknowledges. IMEC in Eindhoven has developed a wireless ECG patch that continuously monitors heart rate and San Diego-based CardioNet has a device that has sold about 100,000 units.

Prof McLaughlin told The Engineer that ST+D’s solution stands out because of the dual advantages of its size and its ability to provide doctors with good-quality information, areas in which competitors fall short.

‘IMEC’s is a miniaturised chip system,’ said McLaughlin. ‘They’ll be coming out with good generic chip technology to eventually make the whole thing very cheap but they aren’t moving into the realm of the extra vital signs and the smart algorithms to process information.

‘CardioNet have a good back-end package designed by Qualcomm and the product is selling quite well. It isn’t, however, as miniaturised as our system. Theirs requires leads going into the electrodes; ours doesn’t require leads because that is taken care for in the patch and therefore motion doesn’t cause too many problems in terms of noise levels.’

McLaughlin believes the market is therefore wide open for VitalSens.

‘Nobody has a lead on this technology at the moment — 100,000 units sold worldwide is peanuts,’ he said. ‘Whoever comes up with the best spec and sensitivity for the ECG detection that will save doctors time will win orders and that is where the competition is going to go now.’

ST+D believes the device will have two main benefits: freeing the patient from otherwise tethered equipment, reducing anxiety and freeing up beds in hospitals. ‘Ten hours after an operation a patient can have the device fitted and be released the following day. It can then be worn for six months for monitoring. This gives the patient reassurance that they are not going to damage their heart. The savings go back to the hospital too,’ said McLaughlin.

The VitalSens wireless device for clinical applications is expected to cost $500 (£250), although McLaughlin anticipates that this figure will fall to $100 or less in the next two years.

Jason Ford