Ambulatory 24-hour double-probe pH monitoring: The importance of manometry

Objective: Historically, manometry has been used for sphincter localization before ambulatory 24-hour double-probe pH monitoring to ensure accurate pl acement of the probes. Recently, direct-vision placement (DVP), using trans nasal fiberoptic laryngoscopy (TFL), has been offered as an alternative tec hnique. Presumably, DVP might be used to precisely place the proximal (phar yngeal) pH probe; however, using DVP, there appears to be no way to accurat ely position the distal (esophageal) probe. The purpose of this study was t o evaluate the accuracy of DVP for pH probe placement using manometric meas urement as the gold standard. Methods: Thirty patients undergoing pH monito ring participated in this prospective study. Each subject underwent manomet ric examination of the esophagus to determine the precise location of the u pper and lower esophageal sphincters (LES and LES). In addition, external a natomic landmarks were used to estimate interprobe distances. A physician b linded to the manometry results then placed a pH catheter using DVP so that the proximal probe was located just above the UES. The results were record ed and compared with those obtained by manometry. Results: Accurate DVP of the proximal pH probe was achieved in 70% (23 of 30) of the subjects. The u se of external anatomic landmarks to estimate interprobe distance resulted in accurate positioning of the distal probe in only 40% (12 of 30) of the s ubjects. Using fixed interprobe distances of 15 cm and 20 cm, distal probe position accuracy was 3% (I of 30) and 40% (12 of 30), respectively. Theref ore, using DV-P, the distal esophageal probe was in an incorrect position i n 60% to 97% of subjects. Conclusion: For double-probe pH monitoring, the p roximal probe can be accurately positioned by DVP; however, there is no pre cise way to determine the interprobe distance required to correctly positio n the distal pH probe. Failure to accurately position the distal probe resu lts in grossly inaccurate esophageal acid-exposure times. Thus, manometry i s needed to ensure valid double-probe pH monitoring data.