Uncomplicated diagnostic tool for gastrointestinal diseases

As food passes through the digestive tract, muscles flex to keep things moving smoothly. Loss of motility can result in acid reflux, inability to transfer food out of the stomach, or constipation.

Dysmotility disorders are often diagnosed with a catheter carrying pressure transducers that detect GI tract contractions. MIT researchers have created a novel gadget inspired by an old Incan technology, the quipu — a collection of knotted ropes used to transfer information — that might offer a cheaper and easier-to-manufacture alternative to existing diagnostics for GI dysmotility.

The MIT researchers and their collaborators at Brigham and Women’s Hospital demonstrated in animal tests that their simple device, a silicone tube filled with liquid metal and knotted many times, produces measurements similar to those produced by the state-of-the-art diagnostic technique known as high-resolution manometry.

“We’re able to make a measurement that would normally require devices that cost thousands of dollars and an instrument that is much more complicated,” says Giovanni Traverso, the Karl van Tassel Career Development Assistant Professor of Mechanical Engineering at MIT, a gastroenterologist at Brigham and Women’s Hospital, and the study’s senior author.

The study’s principal authors are MIT research scientists Kewang Nan and Sahab Babaee, and it was published today in Nature Biomedical Engineering.

Dysmotility Diagnosis

Contractions of the gastrointestinal system are essential for transporting food through the tract, and disruptions of these contractions at any point might result in health concerns. The gold-standard manometry test can be performed to determine if the GI tract muscles are correctly functioning to create those waves.

“High-resolution manometry can detect the pressure and speed of the contractile waves, but those devices are very expensive, in the tens of thousands of dollars, and they require maintenance and sterilising between patients,” Traverso explains.

Traverso (who grew up in Peru) and Nan believed that the Incan technique of quipu may be used to influence the development of a simpler diagnosis. Before writing, the Inca and other ancient Andean cultures employed quipu devices, which are made of colourful threads twisted in various ways, to record information and deliver messages.

“Our objective was to create a device that was equivalent to existing commercially available catheter-based pressure transducers while also lowering the cost and making it easier to build and deploy,” Nan explains.

The researchers started with a basic silicone catheter, which they filled with gallium-indium eutectic, a liquid metal that is harmless in minute amounts, and sealed at both ends. This tube can respond to pressure changes in an unknotted condition, but it is not sensitive enough to detect pressure changes in the gastrointestinal system.

When the researchers added knots at regular intervals throughout the tube, the catheter became considerably more sensitive to pressure fluctuations and could detect pressures up to roughly 200 millimetres of mercury, which is about the greatest pressure encountered in the human digestive system.

The greater sensitivity is due to the knots elongating the cross-section of the tube, making it easier to compress, as demonstrated by the researchers using computer simulations. Furthermore, when the tube is knotted, three or four parts of the tube are stacked on top of one another, increasing its sensitivity to pressure fluctuations.

The researchers also discovered that pressure sensitivity varies depending on the type of knot and how firmly it is tied. The researchers utilised knots spaced approximately 1 centimetre apart to match the spacing of pressure transducers in a manometer for use in the digestive tract, but they might be positioned closer together for other uses, the researchers said.

The researchers utilised the quipu-inspired sensor to monitor pressure in the oesophagus while food was ingested in animal models. They also assessed the rectoanal inhibitory reflex (RAIR). The novel devices produced pressure measures that were comparable to the gold-standard manometry approach in both experiments.

Less complicated option

The researchers also demonstrated that the gadgets can resist high temperatures and can be sterilised using an autoclave, a typical medical equipment used to sterilise things using heat and pressure. This offers them a competitive edge over conventional manometry catheters, which cannot be autoclaved and must be chemically cleaned. Furthermore, because the devices are so cheap to build, they might be thrown after each use if autoclaves aren’t accessible.

“They’re incredibly quick and super cheap to create,” Nan explains. “Another reason for making GI manometers inexpensive and disposable is to encourage decentralised diagnosis. Being inexpensive increases accessibility by lowering costs, and being disposable further aids public acceptability by removing maintenance costs and minimising difficulty during usage.”

The quipu-inspired sensors might be beneficial in locations where current manometry equipment is unavailable, as well as in more industrialised areas as a less-expensive, easier-to-use alternative to manometry.

“I believe that this type of diagnosis might be widely employed in both developing and developed world settings,” Traverso adds. “The next stage is to find possible partners to assist us in manufacturing them, and then test them in patients.”

Walter Chan, director of the Center for Gastrointestinal Motility at Brigham and Women’s Hospital; Johannes Kuosmanen, an MIT technical associate; Vivian Feig, a postdoc at MIT and Brigham and Women’s; Yiyue Luo, an MIT graduate student; Shriya Srinivasan, a postdoc at MIT and Brigham and Women’s; Christina Patterson, an MIT undergraduate; and Ahmad Mujtaba Jebran

The MIT Department of Mechanical Engineering financed the study.