Recently, Respiratory Technology Corporation (dba Restech) announced that the Restech Dx-pH Measurement System was part of a study to accurately measure pharyngeal acid exposure conducted by the Advanced Esophageal Function Laboratory of the University of Southern California (USC). The study, 24-hour Pharyngeal pH Measurement©, was conducted under the direction of Tom R. DeMeester, MD, FACS, FACG, Chair, Department of Surgery, University of Southern California. Recently, the abstract, entitled, Measurement of Pharyngeal pH: A New Technology and Normal Values©, was presented at a poster session at the DDW 2008 Conference & Expo. The Abstract was authored by S Ayazi, JC Lipham, JM Leers, AL Tang, A Oezcelik, E Abate, F Banki, JA Hagen, SR DeMeester, and TR DeMeester).
"We believe that this method of accurately measuring acid in the air passages may represent a significant step forward for improved, more accurate treatment as it confirms acid reflux (AR) is occurring in a patient," said Dr. DeMeester. "The result of our study is the RYAN Composite Score for pharyngeal acid exposure that provides a scale for severity of pharyngeal reflux to assist physicians in making a positive confirmation of the diagnosis."
An alarming increase in the incidence of gastroesophageal reflux disease (GERD) and laryngopharyngeal reflux disease (LPRD) in Americans has led to the need for accurate diagnosis of extraesophageal acid reflux as provided by the Restech Dx-pH Measurement System.
In determining the etiology of conditions such as chronic cough, recurrent laryngitis, sinusitis and asthma, it is important for physicians to be able to rule reflux in or out as a possible contributing factor. Instead of treating 'in the blind' and providing a medication based on symptoms alone, physicians will be able to prescribe treatment based on definitive quantification of acidic reflux in the upper airway.
Studies in normal asymptomatic volunteers indicate that 5.5 is the best pH threshold to identify abnormal pharyngeal acid exposure in the upright period. Normal pharyngeal pH is considerably lower during the supine period, and a lower pH threshold is necessary. Based on studies in normal asymptomatic volunteers, the best pH threshold to identify abnormal pharyngeal acid exposure when supine is 4.5. This provides maximal specificity, limiting the number of false positive tests. In patients with symptoms suggestive of LPR who have normal acid exposure in the supine period at pH 4.5, analysis should be performed using the pH threshold of 5.0, since this will maximize sensitivity, limiting the number of false negative tests.
An algorithm uses the number of episodes, the duration of the longest episode and the percentage of time spent below the three different pH thresholds. These values are used to calculate individual component scores as well as RYAN Composite Score which quantifies the severity of the patient's pharyngeal acid exposure.
Patients with respiratory and laryngeal complaints often have gastroesophageal reflux but classic symptoms are frequently absent and clinical findings are nonspecific. Current methods of measuring pharyngeal acid exposure are often inaccurate due to technical artifacts or probe malfunction. A newly designed pharyngeal pH probe has been introduced which detects aerosolized acid and is placed under direct vision. The aim of this study was to determine normal values for pharyngeal acid exposure using this catheter.
Seventy eight asymptomatic volunteers were recruited. All had esophageal manometry and a video esophagram. Dual channel esophageal pH monitoring was performed with the distal sensor 5 cm above the lower sphincter and the proximal probe 1-4 cm below the upper sphincter. Simultaneously, pharyngeal pH was monitored with the new probe positioned 0.5-1 cm below the uvula. Subjects with abnormal distal esophageal acid exposure, a hiatal hernia larger than 2 cm, or whose study had any technical errors were excluded.
Pharyngeal pH was analyzed using the standard components of esophageal pH monitoring at pH thresholds from 4 to 6 in 0.5 increments and a composite score was calculated. A separate analysis was performed for the upright and supine periods and the 95th percentile was determined.
The study population consisted of 55 subjects (28 M/27F) with a mean age of 31 years (range19-72). The 95th percentile values for pharyngeal acid exposure are shown (Table). In the upright period, 5.5 is the best pH threshold to define abnormal acid exposure (data not shown). Pharyngeal acid exposure is considerably higher in the supine period and a lower threshold is necessary. For this period, pH
Normal values for pharyngeal acid exposure and the composite score are shown:
|% Time Below Threshold|
|Number of Episodes|
|Longest Episode (min)|
|Ryan Composite Score|
A newly designed pharyngeal pH probe may overcome the shortcomings of current techniques. Using this probe we have defined normal values for pharyngeal acid exposure in a large series of normal volunteers. These values can be used to determine if patients with laryngeal or respiratory symptoms have abnormal pharyngeal acid exposure.
Restech Dx-pH Measurement System
The Restech Dx-pH Measurement System is a revolutionary system that comfortably measures pH in the airway. It had been difficult to detect such reflux in the upper airway because, until now, available pH catheters only measured liquid reflux in the esophagus and not the aerosolized form of stomach acid found in the larynx and throat.
Gastric reflux in the upper airway, or laryngopharyngeal reflux, commonly takes a gaseous form that cannot easily be measured using conventional technology. The miniaturized pH sensor at the tip of the Dx-pH Probe is the only sensor able to measure pH in this area. By measuring such pH levels, the Dx-System enables physicians to determine the existence of laryngopharyngeal reflux and to correlate the reflux to various patient symptoms.
The first device capable of measuring pH in the throat in real-time, the Restech Dx-pH Measurement System sends measurements wirelessly to a recording device which is easily carried by the patients during the test period, providing a simple and effective way to monitor reflux. Upon completion of the testing period (usually 24 hours), the patient returns to the physician's office where the device is plugged into a computer and measurements are downloaded for evaluation.
The Dx-pH Probe is 1.5mm in diameter and rests at a comfortable position in the back of the throat behind the soft palate and does not disrupt normal activity or eating. Prior to the development of the Restech Dx-pH Measurement System, physicians testing for reflux had to send their patients home with a probe extending into the patient's esophagus. The positioning and size of those probes were very uncomfortable and interfered with normal activity such as eating and sleeping. The Restech Dx-pH Measurement System allows patients to carry on normal, everyday behavior including eating, exercise, work, bathing, and sleeping with minimal disruption to their lives.
About Restech Corporation
Restech is a leader in engineering world class medical technologies that provide comfortable, reliable solutions to assist physicians in the diagnosis of reflux related health problems quickly and reliably.
The innovative engineering team at Restech is led by professionals with over two decades experience each in medical device development. Together, the Restech staff hold over 30 patents in the areas of sensor technology, data recording & monitoring systems, and other medical devices.
For more information on the Dx-pH Measurement System, please contact Ms. Debra Krahel of Restech at (800) 352-1512 or visit http://www.restech-corp.com.