Mini Robot Fills Esophageal Gap

Pierre Dupont and other researchers at Boston Children’s Hospital developed a small implantable robot that could help save babies born with esophageal atresia and other diseases.

by John Kosowatz
April 09, 2018

A small implantable robot could literally stretch and bridge the gap for babies born with esophageal atresia, a birth defect in which part of the esophagus is missing. The device could be a simpler and much less expensive alternative to the current practice of a lengthy surgical procedure that requires the infant to be immobilized through a medically induced coma and put on a ventilator to breathe.  If further testing is successful, the robot would allow the baby normal movement while stretching the organ and stimulating tissue growth to repair the organ.

“The surgical procedure is morbid, expensive and time consuming,” says Pierre Dupont, senior investigator and chief of Pediatric Cardiac Bioengineering at Boston Children’s Hospital.

A surgeon can easily stretch the esophagus if the gap between the esophagus and the stomach is less than three millimeters. But the organ will snap if it is stretched longer than that, says Dupont, who also holds a Ph.D. in mechanical engineering. Traditional treatment calls for pulling the stomach up to connect to the esophagus, or taking a portion of the infant’s large intestine and using that to make the connection.

Both of those surgeries pose risks, such as aspiration or pneumonia. A newer treatment, called the Foker process, requires the surgeon to suture the ends of the segments and “tunnel” them through the back of the child, where a doctor gradually tightens them to pull the segments together. It can take up to three months to complete the procedure, and sometimes must be repeated if the sutures tear.

“You’re applying traction forces to the two free ends, to pull down and pull up,” says Dupont. “By applying the forces over several weeks, you can reduce the gap and form a complete esophagus. But you have to keep the child paralyzed and sedated.”

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Instead, Dupont’s team developed a tiny tubular robot that uses the principles of the Foker technique to gently apply forces to pull the sections together and stimulate cell growth. “It’s a great mechanical engineering problem,” says DuPont. “You have to apply forces to grow cells but you have to isolate the forces from the rest of the body. The biggest challenge was to create something that would work inside a living body for multiple weeks.”

The cylindrical robot has two rings that are sutured to the ends of the esophagus, or another tubular organ. It is noncorrosive, impermeable to air and water and abrasion-resistant. The rings lightly pull on the segments through an incorporated motor, stimulating cell growth. The robot includes four sensors, two measuring tension and the others displacement of the tissue. It monitors and applies traction based on the tissue properties. The device is controlled with a Bluetooth system housed on a laptop computer.

“It is a computer-controlled device, so you have functionality controlled outside of the body,” he says. The device can measure the forces applied to the organs, and adjust as needed, the tasks now performed by a doctor. But with the robot, the infant can apparently have a normal routine.

The device has successfully been tested in pigs, mimicking the conditions of esophageal atresia, a very rare genetic disease affecting one of about every 4,000 babies born in the U.S. That rarity, however, poses problems for product development. “You’re just not going to get commercial interest based on that,” says Dupont.

But the device can be used on other tubular organs, such as intestines. Dupont’s team is now working on tests for alleviating short bowel syndrome, another debilitating genetic condition. As its name suggests, the condition is one in which there are gaps between segments of the intestines, often requires patients to be fed intravenously, and is much more common than esophageal artresia. Applying the device to the bowel could stoke interest from financial and commercial backers, says DuPont.

“The data suggests only one half of the kids [with short bowel syndrome] get off of intravenous feeding during their lifetime,” he says. “Costs for that can go up to a quarter-million dollars per year. So this potentially could provide enough incentive to push this toward the market.”

The studies so far have been successful, but tissue growth has been an issue within the bioengineering field. DuPont says the body of knowledge at the cellular level is robust, but there is not much understanding of the mechanics at the level of an organ. The team has proven that the device stimulated tissue growth on pigs, and did not simply stretch the segments of the esophagus.

It is well known that tissues grow in response to traction forces, such as during pregnancy when the baby increases pressure inside the mother as it grows. The mother’s skin and abdominal wall increase to relieve tension created from stretching.

“No one still really knows the amount of force needed to induce growth,” Dupont says, but the device can be used in animals to evaluate and measure what forces work best. Until now, this has not been possible. It has been based on the experience of the surgeon. “We don’t know the forces that are applied clinically.”

The results of the esophageal tests were published in Science Robotics. Dr. Dana Damian, formerly a member of Dupont’s team and now a professor at the U.K.’s University of Sheffield, is lead author.