Title:
Swallow evaluation during multichannel intraluminal impedance and pH: an alternate method to assess esophageal transit.

Abstract:
Twenty-four-hour multichannel intraluminal impedance and pH (MII-pH) esophageal monitoring allows detection of both acid and nonacid gastroesophageal reflux episodes. The MII-pH catheter contains 6 impedance segments placed 3, 5, 7, 9, 15, and 17 cm above the lower esophageal sphincter (LES), plus a pH electrode at 5 cm. Multichannel intraluminal impedance and esophageal manometry (MII-EM) allows both functional and manometric evaluation of the esophagus. The MII-EM catheter contains 4 impedance measuring segments (5, 10, 15, and 20 cm above LES) and 5 solid state pressure transducers (within the LES and 5, 10, 15, and 20 cm above LES). Five milliliter saline boluses are given in the recumbent position when performing an MII-EM study. In our laboratory, all patients have an MII-EM study performed before an MII-pH study. In many laboratories, MII-pH is done without earlier MII-EM.
To assess accuracy of swallows given before ambulatory MII-pH monitoring in detecting esophageal transit abnormalities.
Hundred consecutive adult patients, prospectively studied (64 female; mean age = 52.6 y), presenting to our laboratory for MII-EM and 24-hours MII-pH study, also received 10 saline swallows in the recumbent position at the beginning of the MII-pH study. Impedance for these swallows was assessed for the presence of complete or incomplete transit; defined as presence of bolus entry in the 17 cm segment and bolus exit in the 15, 9, and 5 cm segments; defined by a rise in impedance above 50% between baseline and the nadir, and remaining above this value for at least 5 seconds. Of 10 swallows, the presence of 8 or more complete swallows satisfies the MII-EM criterion for diagnosis of complete transit. These findings were blindly compared with those of the 10 saline swallows on the MII-EM study.
In 93% of patients, the MII-pH swallows gave identical transit diagnosis to the MII-EM. In 2 patients, the diagnosis changed from incomplete transit on MII-EM to complete on MII-pH, and in 5 patients from complete transit on MII-EM to incomplete on MII-pH. With both methods, there were 64 patients with complete transit and 29 with incomplete transit. Thus, MII-pH swallows had a sensitivity of 94% and a specificity of 93% for detection of esophageal transit abnormalities.Comparing the swallow diagnosis for each patient, we found that there was a highly significant correlation (P < 0.0001) for the number swallows with complete (Pearson r = 0.89) and incomplete bolus transits (Pearson r = 0.89). There was also a significant correlation (P < 0.0001) in bolus transit time between both methods (Pearson r = 0.64).
Use of 10 saline swallows at the beginning of MII-pH studies is accurate, missing bolus transit abnormality in only 2 of 100 patients. It is also highly sensitive and specific for detection of esophageal transit abnormalities. This method allows detection of patients in whom further evaluation of esophageal function may be warranted.