A new tool developed at the University of Auckland has the potential to detect – and even treat – serious gut conditions.
The flexible electrode records subtle electrical activity in our gastrointestinal system, and inventor Peng Du, from the spin-out company Fleximap and the Auckland Bioengineering Institute, hopes it will become a routine way for doctors to diagnose medical conditions caused when this electrical activity goes awry.
An electrode made using flexible printed circuit technology can be used to map electrical signals in the human stomach. Photo: Peng Du / University of Auckland
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Peng Du holding a rigid electrode that was initially developed by developed by Professor Wim Lammers to detect signals from the gut (left), compared with a more recent flexible electrode (right). Photo: RNZ / Alison Ballance
‘In one end and out the other’ is a good summary of what happens with the food we eat. That food moves through our gastrointestinal system through regular muscular contractions. These contractions are triggered by a series of ‘bioelectric events’ which are similar to the electrical activity that governs the regular rhythm of our hearts – or ‘similar but different’ as Peng Du describes it.
Peng uses the analogy of a network of electric generators. “Each generator on its own is capable of generating electrical current – or frequency - at different times of day. When they are connected together in a network they undergo this physical process called entrainment, which means they lock into a single frequency.”
Imagine, he says, a generator in the north of the North Island that goes on at 9am, while one at the top of the South Island goes on at midday and a third one at the bottom of the South Island goes on at 3 pm.
“This sequence in time allows a direction of propagation,” says Peng. The same thing is happening in our long skinny gut, as waves of electrical activity ripple along it in an entrained sequence, stimulating the muscular contractions.
But if enough of the individual generators stop working, the whole system can develop arrhythmias, get out of sync and even stop.
The Fleximap team is continually refining the flexible electrodes. The white bulbous piece of plastic is a life-sized model of the human stomach. Photo: RNZ / Alison Ballance
Until now, measuring both healthy and disrupted electrical activity in the gut has proven very difficult, as the electrical signals are much more subtle and diffuse than those of the heart.
But Peng’s team, which includes engineers and medical specialists, was the first to measure and confirm that two conditions - gastroparesis (effectively paralysis of the stomach) and chronic nausea and vomiting – are related to abnormal electrical activity in the gut.
These conditions are uncommon, says Peng, but are increasing as they are related to Type 2 diabetes. And he suspects that the much more common dyspesia, or indigestion, is also related to abnormal electrical activity in the stomach.
Peng Du with the 'torso tank' used to calibrate how electrical signals produced in the gut propagate across the body's surface. Photo: RNZ / Alison Ballance
The first sensors developed to map electrical activity in the gut were rigid, but Peng says the trick has been to develop a flexible electrodes that can mould to the contours of our soft gut.
He uses printed circuit board technology to produce a sensor that has multiple electrodes embedded on it in a regular pattern.
The effectiveness of the first device was tested in real people who were having gut surgery at Auckland City Hospital, when the device could be laid directly on the stomach.
The tool is so sensitive, says Peng, that it showed that different parts of the stomach have different functions, and unique patterns of electrical activation.
A key design consideration has been to meet the high standards of sterility required in an operating theatre, so Peng and his team are constantly refining. A bulky soldered connector that was difficult to sterilise has been replaced by a small integrated plug. Everything has been made smaller and thinner so it can be used during keyhole surgery, and not just open surgery. And the team is working to better understand the patterns of gut signals, so they can develop a tool that could be used on the exterior of the body.
Sarah Jeong holding the electrogastrography belt, which is covered with electrodes to measure electrical signals from the gut. Photo: RNZ / Alison Ballance
Student Sarah Jeoing is already using an external gastric belt to study how much discomfort and nausea people experience when they’re in a virtual reality or VR environment.
Peng and Sarah say that the VR industry is busy trying to find ways to minimise that kind of discomfort – and their tool will help quantify how effective they are. It’s another useful commercial application for the company that Peng has developed out of this research, called Fleximap.
Peng is a Rutherford Discovery Fellow, and part of the MedTech Centre of Research Excellence.
