Analysis of pH dynamics in the distal esophagus utilizing pH histograms and acid clearance values

Abstract

Existing scoring systems for 24-h esophageal pH recording rely heavily on total duration of acid reflux; little is known or understood of the significance of dynamic aspects of esophageal acid clearance. The 24-h pH profile and rate of acid clearance in the lower esophagus was analyzed in children with clinical features of gastro-esophageal reflux (GER). Twenty-four-hour histograms of pH and time were developed with whole-pH data obtained by 24-h pH monitoring, and values for acid clearance were calculated from actual pH curves. The acid clearance value represented the average time in seconds to recover 1 pH unit from the lowest pH to pH 4.0. Clearance values greater than 100 s/pH were considered to be abnormal. Sixty-six recordings were analyzed. Five types of pH profile were characterized: (1) a “normal” pattern in which esophageal pH did not fall below pH 4.0 and the acid clearance value was 67.9 ± 41.1 s/pH (mean ± SD); (2) a “long-tail” pattern with a moderate number of reflux episodes and rapid acid clearance. The mean acid clearance value was 78.1 ± 46.4 s/pH; (3) an “intermediate” pattern with esophageal pH at or near 4.0 for prolonged periods where the mean acid clearance value was significantly delayed (285.6 ± 109.8 s/pH); (4) a “pseudo-GER” pattern with moderate reduction in pH during reflux episodes, but with prolonged acid clearance. The mean acid clearance value was 175.1 ± 93.0 s/pH; and (5) a “GER” pattern; this was associated with either infrequent acid reflux and delayed acid clearance, or frequent reflux episodes and rapid acid clearance. The mean acid clearance value was 160.3 ± 113.6 s/pH. Dynamic analysis of acid clearance in the esophagus may be useful therapeutically.