The small radio-frequency monitor measures both acid and nonacid reflux.
A wireless implant that monitors esophageal reflux could produce more-accurate results for doctors and more comfort for patients than current technology. The device incorporates radio-frequency identification (RFID) and tests for electrical impulses that indicate acid and nonacid reflux. Information is transmitted to a sensor worn outside of the body.
The patent-pending device aims to solve two key design issues in monitoring reflux—accuracy and patient comfort. “For esophageal cancer screening, the endoscopy and catheter process is [often] too painful for patients, so by the time they go into the doctor and find out they have cancer, it's too late,” says Jung-Chih Chiao, PhD, associate professor at the University of Texas at Arlington. “If there's a comfortable and more convenient way for the patient, then more [individuals] who have even minor symptoms of heartburn might want to do this screening.”
In addition to the discomfort experienced by some patients, current approaches don't address both acid and nonacid reflux. Currently, a catheter is inserted through the patient's nose and into the esophagus. This makes it difficult for the patient to continue normal activity, which in turn gives doctors less-accurate measurements. A wireless monitoring system that's about the size of a vitamin pill is already on the market, but it doesn't measure nonacid reflux, says Chiao.
Chiao and his colleagues at the University of Texas Southwestern Medical Center (UT Southwestern; Dallas) are confident that their device, which doesn't require a catheter, can distinguish air, water, and different types of acid. The wireless sensor uses impedance monitoring to detect nonacid reflux. “Impedance sensing is accurate because we can sense the direction of the food flow,” says Chiao.
The team at UT Southwestern Medical Center includes (from left to right)
Jung-Chih Chiao; H. F. Tibbals, PhD; and Shou-Jiang Tang, MD.
To refine the design, the team created three generations of prototypes. The first 2 × 2-cm sensor is built on a flexible substrate, which allows it to be rolled up and then inserted into the esophagus. There, it attaches to the esophageal wall and an inductive antenna resonates with a wireless device outside of the body. This beeper-type device receives electromagnetic signals from the esophagus and stores the data. Doctors could download the information, and a computer could analyze the data. No battery is needed, and the sensor lasts more than 48 hours.
The second-generation sensor, about the size of a capsule, incorporates an RFID chip. The chip identifies the position of the implant and provides a secure communication with the external reader. It also eliminates motion artifacts, which can cause false readings.
For the third-generation sensor, researchers used a thermal-treated polymer that is biocompatible and resists acid. They tested it to withstand more than 2 weeks in the body. Their target size for the unit, which Chiao hopes to use for animal tests, is 0.8 × 0.5 cm.
The next challenges include making the unit disposable and finding an inexpensive manufacturing method. The researchers have also been working closely with doctors to make it easier to attach to the esophageal wall.
Although the researchers aren't developing software to work with the chip, Chiao says that a device company's involvement in designing that component could help take the device to the marketplace. Software would have to be included in the final device to handle the large amount of data from the sensor. The signals need to be coordinated with patient activity during reflux or nonreflux situations, explains Chiao.
The team is also looking at using the device to diagnose other diseases. “This is an enabler technology. Once we establish the fundamentals, there are a lot of [other] applications.”