Figure 6 - Tracing derived from an ambulatory dual (esophageal, pharyngeal) pH study.

In this example of a pathologic regurgitator, the distal pH electrode is in the standard position 5 cm above the lower esophageal sphincter. The proximal electrode is positioned 1 cm above the upper margin of the UES. Note the two major periods (shaded) in which some of the episodes of esophageal acidification are also associated with pH drops in the pharynx. Note also that this individual regurgitates exclusively in the upright posture during the day, but does not regurgitate at night (marked with "S")