Wireless esophageal pH monitoring: new technique means new questions.

INTRODUCTION: The introduction of wireless pH monitoring has been touted as a significant advance in the diagnosis of gastroesophageal reflux and associated disorders. We prospectively enrolled patients in a research registry to assess the feasibility and safety in clinical use.
METHODS: All patients undergoing endoscopy with wireless pH studies (Medtronic Bravo pH system) for a 12-month period starting in April 2004 were prospectively enrolled. Probes were placed 6 cm above the endoscopically localized squamocolumnar junction. Successful completion was defined as at least 24 hours of pH recording. Safety data were obtained by review of patient diaries. All results are given as median with 25% to 75% confidence interval (CI).
RESULTS: A total of 217 studies with endoscopy and capsule placement were performed (65% women; median age, 51 years; range, 42-58 years) and included in the study; 1 patient refused participation in the registry and 5 studies were performed without preceding endoscopy and were excluded from this analysis. The pH study was successfully completed in 95.1%; early capsule detachment (1 hours; CI, 0-5 hours) or receiver malfunction occurred in 7 and 2 cases, respectively. There were no immediate adverse effects; 18 patients (9%) complained about significant chest discomfort, associated with odyno- or dysphagia, requiring removal of the capsule in 3 patients (1.5%). Of the completed studies, 56% were abnormal with 32.2% being abnormal on both days, whereas 16.1% and 6.9% only showed increased acid exposure on day 1 or 2, respectively. The higher likelihood of abnormal results for day 1 was associated with a significantly increased esophageal acid exposure during the first 6 hours after capsule insertion on day 1 (total time with pH < 4: 6.9%; CI, 3.2%-16.5%) compared with the corresponding time on day 2 (5.0%; CI, 0.9%-10.8%; P < 0.01), without differences esophageal acidification during the remaining time or differences in recorded activity.
CONCLUSIONS: Using a large registry of patients with suspected gastroesophageal reflux symptoms, our data show that wireless pH studies can be safely completed in more than 90% of patients. Whereas variability during prolonged recordings should be expected, the significantly higher likelihood of abnormal findings during the initial period of pH monitoring suggests a systematic influence of endoscopy and associated premedication, typically performed prior to capsule insertion, which needs to be considered when pH data are analyzed.