I don't think "dual probe" means two wires. It just means that it measures reflux in two places..one at the traditionally low GERD diagnosis location, and one higher up, so that it can monitor what reflux makes it that high.
Here is a Wikipedia quote that might be helpful:
pH monitoring in laryngopharyngeal reflux
Retrograde flow of gastric contents to the upper aerodigestive tract causes a variety of symptoms such as cough, asthma and hoarseness. These respiratory manifestations of the reflux disease commonly called laryngopharyngeal reflux (LPR) or extraesophegeal reflux disease (EERD). Distal esophageal pH monitoring has been used as an objective test to establish reflux as the cause of the atypical reflux symptoms but, its role in causally associating patients’ symptoms to GERD is controversial. In an effort to improve diagnostic accuracy of testing, a catheter with two pH senors has been used to measure the degree of esophageal acid exposure in both distal and proximal esophagus. The ideal location for pH measurement to confirm the diagnosis of the laryngopharyngeal reflux is pharynx and new studies has focused on the development of a new pH sensor which can function in the challenging environment of the oropharynx.
Here's a short abstract regarding a study of the value of using dual probe monitoring in diagnosing LPR symptoms.
Hope this information is helpful. I know it's hard to navigate the information. They need to write a "GERD for Dummies" book, don't you think?
Best wishes in your quest!
Words of wisdom by Eckhart Tolle:
"Whatever you fight, you strengthen, and what you resist, persists.”
“Worry pretends to be necessary but serves no useful purpose”
“Accept - then act. Whatever the present moment contains, accept it as if you had chosen it. Always work with it, not against it.”