Esophageal pH monitoring: are you sure that the electrode is properly placed?

OBJECTIVE:A crucial methodological aspect of ambulatory 24-h esophageal pH monitoring is electrode placement. Lower esophageal sphincter (LES) location is recommended for standard electrode positioning. The aim of the present study was to evaluate prospectively whether LES manometric location and intragastric pH acid confirmation suffice to guarantee that the pH electrode is properly placed.METHODS:We evaluated data from 402 consecutive patients undergoing esophageal pH monitoring. LES location was determined by manometry, and the pH electrode was introduced until a pH recording <3 was obtained. Subsequently, it was positioned 5 cm above the proximal LES border. Thereafter, adequate catheter placement and absence of bends or loops were checked by fluoroscopy. Patients with bent or rolled catheters were instructed to have breakfast immediately, and catheter placement was checked again by fluoroscopy.RESULTS:When checked by fluoroscopy, the catheter was properly placed in 383 patients (95.3%). In the other 19 (4.7%), it was not located in the distal part of the esophagus owing to bending or rolling: 14 in the esophagus and five in the pharynx. After breakfast, 14 of the 19 malpositioned catheters were properly positioned whereas five remained bent or rolled. Those bent in the esophagus were more prone to unbending (12 of 14) than those bent or rolled in the pharynx (two of five).CONCLUSIONS:After LES location by manometry and demonstration of acid pH during the pH step-up technique, the pH electrode was properly placed in more than 95% of cases. Nevertheless, it cannot be completely guaranteed that the pH catheter will not bend or roll, and the pH electrode will not be malpositioned. Eating immediately after electrode placement resolves this problem in the majority (75%) of cases. Therefore, we recommend that patients undergoing esophageal pH-metric studies be instructed to eat as soon as possible after electrode placement to minimize these possible pitfalls.