Medical Device Daily

Ross Tsukashima, director of product development at Restech (Respiratory Technology; San Diego), may sound like he is stating the obvious when he points out that “the throat is not the esophagus.“ But it is an important distinction for monitoring gastric reflux.

The esophagus can withstand up to 50 reflux episodes a day without trouble, he told Medical Device Daily. But if the gastric juice makes it all the way up through the upper sphincter and into the back of the throat – a condition known as laryngopharyngeal reflux (LPR) – this more sensitive area can be damaged.

“The acid that comes up from the stomach is very caustic, it's pH. When it gets up into an area where it doesn't belong, it can cause a lot of problems, obviously with the lungs, but also with the throat, things such as ear infections, sinus problems – it just sort of wreaks havoc in that area,“ Tsukashima said.

Restech has developed the Dx-pH Measurement System to help doctors assess aerosolized acid in the esophagus or pharynx. The company said it is the first device to measure and record pH in the oropharynx for detection of LPR in real time.

pH levels have traditionally been monitored in the esophagus. “Because the traditional esophageal sensors are not designed to work up in the pharynx area, we feel that [they are] missing a lot of episodes,“ he said. Conventional pH sensors are limited by their placement – too low to detect LPR; their discomfort to the patient; and the need for direct fluid contact between the reference sensor and the pH sensor.

Tsukashima says Restech's Dx-pH Monitoring System is the first device designed to work in the pharyngeal area, though it can also be used in the esophagus. “When exposed to liquids, it will work just like a regular pH sensor,“ he notes. “But its true advantage is the fact that when pulled up into this place where there is not a lot of tissue contact, not a lot of moisture, it will still work.“

The small 1.5 mm-diameter catheter is placed transnasally and is positioned behind the soft palate. The patient-friendly device is more comfortable than larger catheters that stretch down a patient's lower esophagus, he said. “Because it doesn't go past the epiglottis, which is the swallowing portion of the throat, it doesn't hurt as much. So [patients] can wear it for 48 hours, which also increases the sensitivity of the device.“

Restech calls the positioning of the Dx-pH device “revolutionary.“ The device rests three centimeters higher than the conventional pharyngeal sensor, eliminating the need for manometry to determine proper positioning. A visual signal indicates when the Dx-pH is properly placed. “When we see the blinking light at the end of the catheter we know it has advanced far enough that it is not in the sinus cavity, and we also know then that the catheter has made it around the bend in the throat and is aiming in a downward position, which is in the correct location for us to measure pH.“

This downward positioning also reduces mucosal masking, and the teardrop shape of the sensor reduces fouling and boosts specificity, the company said. “The sensor is at the very tip of the catheter, so if any reflux events come up, it's going to hit it head on,“ Tsukashima said. He explained that traditional sensors are located on the side of the catheter, “where there is about a 50% chance of being covered up by tissue.“

Another advantage of Restech's device is that the coplanar ionic bridge pH sensor is self-condensing, and therefore does not require immersion in liquid as with conventional sensors. In addition, the pH readings occur at a 2 Hz sample rate, which is 10 times the frequency of current pH systems.

Tsukashima said the company has a “pretty broad market“ for the device, commercially available since October, including sleep labs, pulmonologists, ENTs, gastroenterologists and pediatric physicians.

The Dx-pH Measurement System was most recently showcased at the Association of Polysomnographic Technologists meeting, part of the SLEEP 2006 Associated Professional Sleep Societies event last month in Salt Lake City.

Also unveiled at the meeting was the Restech Dx–Sleep Adapter, a new accessory for the Dx–pH system. Released in February, the Dx-Sleep Adapter allows sleep medicine professionals to track patients' airway pH events in real-time on their existing sleep monitoring equipment, which aids in the differential diagnosis and monitoring of disorders such as asthma, obstructive sleep apnea and LPR.

The “plug and play“ adapter connects to the Dx–Recorder on one end while the opposite end plugs directly into a polysomnograph (PSG). The minimally invasive Dx–pH Probe is introduced via the naris and seated behind the uvula. Oropharyngeal pH data is collected and sent wirelessly from the Dx–Transmitter to the recorder during the study period. The Dx–Sleep Adapter then transfers the data to a sleep center's PSG equipment.

Founded in September 2003, the start-up company is focused on developing medical technologies that provide comfortable, reliable solutions to assist doctors in the diagnosis of acid-related health problems quickly and reliably. “We have several new products in the pipeline,“ in this area, Tsukashima said, though declining to go into detail. Privately held, Restech has raised $3.5 million in equity capital to date and is in the process of completing a $1.0 million convertible debt offering.

Restech also is working with researchers at Emory University (Atlanta) and the University of Southern California (Los Angeles) to study LPR and methods to detect pH in the upper airway.

Tsukashima, one of the inventors of the Dx-pH system who also helped design the Bravo pH monitoring system now sold by Medtronic (Minneapolis), defined what may be the most important advantage of Restech's device: “This pH monitoring system will break down existing barriers in performing pH monitoring that allows greater acceptance by physicians and their patients.“

“We get a lot of interest,“ he said. “We hear a lot of people say, 'we used to do pH, but it was just so much work we stopped doing it.' When they hear about the advantages of sensitivity, specificity, all these things [that the Restech system offers], they say 'we're ready to try it.'“