In 2011, UC San Diego bioengineer Todd Coleman developed some thin, flexible sensors that could measure electrical activity in the brain.
That same year, his father died of pancreatic cancer. His grandmother died from stomach cancer years before.
That got Coleman thinking.
“Are there electrical rhythms of the digestive system? Maybe we could measure them with these new devices, and maybe this could help solve some of the problems that have been associated with my family," he wondered.
Stomach’s Electrical Signals
Researchers had used external sensors to measure the electrical activity of the digestive tract before. But Coleman said they failed to take one crucial factor into account.
“Every person’s stomach is in a slightly different location on their body," he said. "And people were not taking that into consideration where they placed the electrodes. So if you’re placing the electrodes far away from the stomach, it’s not surprising we don’t pick up anything meaningful.”
Coleman also discovered that the stomach’s electrical signals are quite faint — about 10 times weaker than the heart’s.
So Coleman had to develop some extremely sensitive hardware. Coleman’s team began testing a device in 2013.
Their research is published in the March 22 issue of Nature's open-access journal Scientific Reports.
Their current version is a bit smaller than a cell phone. It uses six electrodes that are attached to different parts of the abdomen.
One of the first guinea pigs was postdoctoral fellow Armen Gharibans. He tested the device on himself for more than a year.
Interpreting data
"It starts recording locally onto a micro SD card," Gharibans said, as he attached the device to his abdomen. "And after about 24 hours we can turn it off, take the data off, download it and analyze it on the computer off-line.”
Interpreting the data is a challenge, Gharibans said, because the device picks up signals from the heart and respiratory system, as well as from body movement.
“And so you have to basically try to separate out only the stomach activity, and moreover do some new analysis to look at things like the spatial propagation and the frequency and the speed of that signal,” he said.
Pediatric gastroenterologist Hayat Mousa, who practices at Rady Children's Hospital, tested the device on 11 of her patients.
She said the standard method of monitoring digestive activity, called esophageal manometry, relies on a long catheter that’s inserted into the stomach.
“To place those catheters we have to place the pediatric patient under anesthesia, and to place a stiff catheter in the nose or the mouth," she said. "It’s not very comfortable for them when they wake up. And after we place it, we keep it for at least eight to 10 hours.”
A spatial histogram
Mousa said Coleman's device performed as well as a catheter. And it's much easier for patients.
Coleman says he can use data from the device to produce what’s called a spatial histogram. These show, for example, what fraction of the time waves in the stomach are moving toward the small intestine. In other words, they show how often the stomach is working properly.
“If you take a look at subject C here," he said, pointing to a histogram on a computer screen, "notice that the waves are propagating all over the place. They’re equally likely to be propagating in any direction. So for this subject, it’s not surprising that they have a lot of nausea, because half the time, it’s pushing in the opposite direction.”
The Centers for Disease Control and Prevention says in 2015, digestive problems prompted more than 32 million visits to the doctor.
It turns out many digestive disorders have the same symptoms. Coleman hopes to perfect his device so that one day, it may be able to pinpoint the cause of a person’s problems.
