The role of impedance monitoring in patients with extraesophageal symptoms.

OBJECTIVES/HYPOTHESIS: Ambulatory esophageal impedance monitoring is commonly employed to assess for nonacid reflux in patients with extraesophageal reflux. We aimed to determine if on therapy impedance data can be predicted from off therapy upper endoscopy, manometry, or pH parameters. STUDY
DESIGN: Prospective Cohort Study.
METHODS: Patients with extraesophageal reflux symptoms and either partial- or nonresponders to twice-daily PPI underwent impedance monitoring on twice-daily PPI, as well as manometry, upper endoscopy, and 48-hour wireless pH monitoring off acid-suppressive medications for 1 week. Percent time pH < 4 and number of reflux episodes were obtained. Multivariable linear regression was used to determine association between the impedance data on therapy and upper endoscopy, manometry, and pH parameters measured off therapy.
RESULTS: Seventy-five patients (77% female, median BMI 29, 38% with hiatal hernia, and 19% with esophagitis) were studied both on and off therapy. Thirty-five percent had abnormal impedance monitoring on therapy and 84% had abnormal pH testing off therapy. There was no significant (P = 0.184) overall correlation between total number of impedance events and the baseline physiologic parameters of hiatal hernia, degree of acid reflux, or manometric findings, with only weak correlation (r = 0.54, P = 0.045) with % time pH < 4 among patients with esophagitis.
CONCLUSIONS: In patients with suspected extraesophageal reflux refractory to PPI therapy, impedance measures on therapy cannot be predicted from traditional baseline esophageal physiologic parameters. We recommend caution regarding over-interpretation of impedance data. LEVEL OF EVIDENCE: 2b.