A team of researchers has developed a wearable, non-invasive
system to monitor electrical activity in the stomach over 24 hours—essentially
an electrocardiogram but for the gastro-intestinal (GI) tract.
Applications include
monitoring GI activity for patients outside of a clinical setting, which cuts
down costs. Monitoring for longer periods of time also increases the likelihood
of capturing abnormal events.
Researchers detail their
findings in the March 22 issue of Nature's open access journal Scientific Reports.
The team tested the
device, a 3D printed portable box connected to 10 small wearable electrodes, on
11 children and one adult volunteer. They found that data collected with the
wearable system were comparable to data collected in the clinic with
state-of-the-art methods, which are invasive—including a catheter inserted
through the patient's nose. They also found that the stomach's electrical activitychanges not only around meals, but also
during sleep, following its own circadian rhythm.
"We think our system
will spark a new kind of medicine, where a gastroenterologist can quickly see
where and when a part of the GI tract is showing abnormal rhythms and as a
result make more accurate, faster and personalized diagnoses," said Armen
Gharibans, the paper's first author and a bioengineering postdoctoral
researcher at the University of California San Diego.
Todd Coleman, the paper's
corresponding author and a UC San Diego professor of bioengineering, agrees.
"This work opens the
door accurately monitoring the dynamic activity of the GI system," he
said. "Until now, it was quite challenging to accurately measure the
electrical patterns of stomach activity in a continuous manner, outside of a
clinical setting. From now on, we will be able to observe patterns and analyze
them in both healthy and unwell people as they go about their daily
lives."
Physicians involved with the study say the device meets an
unmet clinical need.
"This will help us
determine if the stomach is functioning properly during meals and - most
importantly - when patients are experiencing symptoms such as nausea and belly
pain," said Dr. David Kunkel, one of the paper's co-authors and a gastroenterologist
at UC San Diego Health.
The breakthrough was made
possible because engineers and physicians came together to work on the problem,
said Benjamin Smarr, one of the paper's co-authors and a chronobiologist at UC
Berkeley.
Better algorithms
The researchers' biggest
challenge was designing algorithms that recognize and boost the stomach's
electrical signals amid noise and artifacts. This is especially difficult to do
because the stomach's electrical signals are 10 times weaker than the heart's,
making them harder to capture and analyze.
Researchers harnessed the
signal processing expertise in Coleman's research group to develop a
sophisticated algorithmic pipeline that can clean up the data and separate out
abdominal muscle activity (for example when a person walks), heart beats and
gastric activity, into different bands of signals that do not overlap. As a
result, clinicians can examine each signal individually and compare it to
others.
The device and testing
The device itself uses
off-the-shelf electrodes used in electrocardiograms. The electronics and
battery are encased in a 3D printed box and connected to the electrodes, which
fit on a person's abdomen just over the stomach.
The researchers worked
with Dr. Hayat Mousa and tested the device on 11 pediatric patients at Rady
Children's Hospital in San Diego. These patients had been undergoing an
invasive procedure called manometry, one of a couple clinical gold standards
for objectively monitoring GI tract activity. The procedure requires using a
catheter inserted through the nose to measure pressure at several points inside
the stomach. Comparing the two methods showed that data collected
by the wearable device was robust and reliable.
"I have been
practicing pediatric gastroenterology and taking care of patients for 20
years," Dr. Mousa said. "The only method to assess gastrointestinal
motility involves placing motility catheters in the GI tracts while kids are
sedated or under general anesthesia. It has been a long journey discussing the
benefits of doing such an invasive procedure with my patients and their
families. My challenge has always been finding a test that offers a
non-invasive assessment of the enteric nervous system and its connection with
brain function."
"The technique
outlined in this paper is the best way to evaluate children with motility and
functional GI disorders," Dr. Mousa added. "It provides the
information without need for sedation and it offers the flexibility to monitor
kids while they continue their daily activities. This procedure allows
convenience without compromising accuracy. In addition, it offers the option to
assess the brain-gut response to therapeutic interventions including
biofeedback and neuromodulation."
The system is currently
paired with a smart phone app that allows patients to log their meals, sleep
and other activities. The long-term goal is to design an app that would allow
patients and physicians to see the data collected by the device in real time.
"This is analogous to
going from switchboard operators straight to smart phones for
gastroenterology," Smarr said.
