Surfing An Acidic Wave:

PH Monitoring Technologies Swim in Sea of Innovation

Americans' love of fast foods and high-fat diets, in combination with more stress and less exercise, has led to an increase in digestive disease. One must go no farther than the television set -- where commercials for prescription acid blockers support the network news -- to see how this change in lifestyle has affected everything from our economy to our national well-being.

With increased rates of gastrointestinal reflux disease (GERD), the number of prescriptions for Nexium and Prilosec has shocked even the most optimistic pharmaceutical analysts. Prilosec costs about $4 per day and has become the top-selling pharmaceutical worldwide with more than $6 billion in sales annually -- much to manufacturer AstraZeneca's delight.¹

Increased illness rates bring engineers and other members of think tanks looking to capitalize on the latest innovations to aid those in need. Fitting this pattern, scientists are furiously working to improve pH monitoring systems -- created to determine a patient's stomach and esophageal acidity levels.

Tried and True

David Brown, U.S. business development director of Oakfield Instruments, says the company's Flexilog system is a gentle diagnostic procedure that requires no sedation. The traditional pH monitoring system utilizes an esophageal catheter that monitors a patient's levels of gastric acidity.

"It is a catheter-based system with one or two channels," he says. "It uses antimony crystal catheters which are 1.5 mm to 2.1 mm in diameter. Also it uses either an internal or external reference catheter and will monitor the pH in the esophagus typically 24 to 96 hours. Most people would not be tolerant up to 96 hours, but the instrument will monitor that long if necessary."

The Flexilog system has been on the American market for about four years. Brown says the complete system typically sells for $10,000. While the electronics and software are permanent, the catheters can be either reusable or disposable. The system can also be used in pediatric patients and in seniors.

The innovative design of the Flexilog system is found in the minute diameter of the catheter.

"Because our instruments are so small, the gag reflex is minimal," he says. "If you were going to put an endoscope down the esophagus, the gag reflex would be much greater. The intubation, the placing of the catheter, is done upright, which also minimizes the gag reflex. If you were doing it with the patient lying down, the catheter would rest on the back of the throat, acerbating the gag reflex."

"The procedure our instrument supports is the gold standard operative diagnosis," he says. "You won't get a surgeon carrying out a keyhole surgery to fix a sphincter issue, a GERD issue, without the procedure that our instrument and consumables support."

Brown says the time it takes to place a Flexilog system depends on the desired result.

"If the physician wants a full whole lower esophageal sphincter, LES characterization, so he or she knows precisely where that is, the endoscopy team would place the pH catheter 5 cm above it. The procedure can take 30 to 45 minutes. If the endoscopy team is less precise and they want to place the pH catheter in the stomach and then do a pull-through to identify the bottom end of the sphincter and then estimate the width of sphincter so they can get it 5 cm above, this is much less accurate but also [takes] much less time. They could be in and out within 30 minutes."

While recently visiting a hospital to observe, Brown says he nearly underwent the procedure he knows so much about.

"A nurse threatened me with the system," he says, laughing. "I watched her do two and at the end of the second procedure, I thought I might take her up on it. I knew I could trust this person, but she didn't threaten me again."

Oakfield Instruments, which is based in the United Kingdom, recently expanded to the United States with an office in Raleigh, N.C. Brown says 28 Flexilog systems have been sold in the United States to date, with thousands sold in Europe.

Capsule Conundrum

Officials at Medtronic, based in Minneapolis, wanted to improve the traditional pH monitoring system -- one that requires use of a esophageal catheter and monitor for 24 hours or more. Rather than "tethering" their patients, says a spokesperson for Medtronic, the Bravo pH Monitoring System implants a capsule in the esophageal wall and has the patient wear a pager-sized monitor.

"The capsule is placed endoscopically," she says. "The patient is sedated, the mouth block is in, they put the scope in and find the necessary measurements. They pull the scope out, put the Bravo system in and the capsule is attached to a proprietary delivery system. The capsule sits on the distal end of the system, which is placed in the patient's mouth and down into the esophagus. The endoscopy team lines up the markings on the delivery system and the capsule is attached in a multi-step process."

The five-step process, she says, implants the capsule which immediately begins monitoring acidity levels.

"There is a suction chamber on the side of the Bravo capsule," she describes. "The working end of the delivery system, which the physician has in his hand outside of the patient's body, is a port, which they attach to a little pump. They turn the pump on to 550 psi and keep it on for 30 seconds. Mucosa is sucked into the port. There is a plunger on the end of the delivery system that basically drives a little pin or needle into the tissue that has been suctioned into the chamber. The physician rotates the handle and springs it back, which releases the capsule. They then remove the entire delivery system and throw it away."

Medtronic says the capsule will stay implanted for several days, although the system was only designed to monitor for 48-hours.

"The capsule stays in place during the duration of the test and for seven to 10 days," Medtronic says. "Then, through turn-over of cells, it will slough off and move through the patient's system naturally."

While traditional systems monitor for 24-hours, Medtronic says the additional monitoring window used by the Bravo system was a matter of physician preference and convenience.

"Patients will tolerate (this test) better," the spokesperson says. "The physicians feel the more data they get, the better ... it is for them to make a diagnosis."

Additionally, she says, the option of not having to use a catheter is ideal for many patients.

"The test is measuring the same thing," she explains. "It is just that the way the capsule is relaying the information is different. Patients love the flexibility. They can sleep and shower comfortably."

The Bravo system, which became available on the market in September 2000, is solely for adults. The cost of the system is proprietary information. Medtronic says the system is not intended to entirely replace traditional pH monitoring systems -- which Medtronic also manufactures.

"This is not a complete transition (from traditional to a capsule system)," she says. "Bravo is a great option for many people, but contraindicated for those with pacemakers, difibrillaters or nerve stimulators."

Officials at Sandhill Scientific in Highland Ranch, Colo., also manufacture a pH monitoring system, GERDcheck. For more information about their system, see the February/March 2002 issue of Endonurse, or visit www.endonurse.com/articles/231feat5.html. You may also access Sandhill's Web site at www.sandhillsci.com. 

For more information about the Flexilog or Bravo monitoring systems, visit: www.flexilog.net and www.medtronic.com.

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