Relationship of intraluminal pH and pressure within the lower esophageal sphincter

To determine the relationship between lower esophageal sphincter (LES) intraluminal pressure and its intraluminal pH, we studied six healthy volunteers. We recorded intraluminal pressure and pH concurrently using rapid pull-through, slow pull-through, and station pull-through, as well as, rapid push-through and slow push-through techniques. The results showed that LES length was 35 +/- 4 (SE) mm by RPT and 30 +/- 3 mm by SPT. The pressure was maximal in the proximal half of the LES. On rapid pull-throughs, the intraluminal pH rose from about 1.5 to reach a value of about 2.5 at the peak of the high pressure zone. With continued withdrawal into the esophageal body, the recorded pH rose minimally to about 3-4. On push-throughs, the pH recorded along the LES was the same as that of the esophageal body. After the electrode cleared the LES, the pH abruptly fell to gastric pH. During station pull-through with the electrode 0.5-1.5 cm proximal to the distal LES margin, transient pH drops were observed with swallows. With rapid swallows, however, the pH drop did not occur until after the last swallow. This finding suggests that the pH drops with swallows were due to axial LES movement rather than gastroesophageal acid reflux. We conclude that 1) the relationship of the gastroesophageal pH transition zone and LES high pressure zone is better defined by a sphincter push-through than a pull-through; 2) the transition between gastric and esophageal pH occurs either at or slightly distal to the distal LES margin; and 3) swallow-induced axial LES movement may cause spurious recording of acid reflux when the pH probe is positioned within the distal half of the LES.