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Combining GERD tests allows strengths and weaknesses of each method to be identified in detecting and characterizing reflux (RE). Aim of this study was to compare two methods that measure bolus volume of a refluxant (impedance monitoring (Imp) and manometry (common cavity)) to pH monitoring which measures changes in acid concentration of a refluxant. Nineteen symptomatic GERD patients and 10 normal volunteers were studied before and after a meal. All had 2-hr simultaneous manometry, pH, and Imp (six sites: 3, 5, 7, 9, 15, 17 cm above LES). Reflux by pH was a fall in pH from above to below 4. There were 973 RE's in all subjects, but only 19% were detected simultaneously by all three methods. Imp detected more RE's (96%) than manometry (76%) or pH probe (28%). Imp was the only method to detect 15% (144/973) of RE's, while detection only by pH probe (2%) or manometry (2%) was rare. Most RE's detected by Imp were detected simultaneously by manometry (75%,720/937). Those not detected by manometry were usually in blind spots either in the vulnerable period 2-3 sec after a swallow, during a posture change, or during a Valsalva. Most RE's detected by Imp were not detected by the pH probe. Though most liquid RE's fasting were detected by pH, most liquid postprandial RE's were not, due primarily to weakly acidic rather than superimposed acid RE's. Bolus clearing time by Imp and manometry was nearly identical, while acid clearing was threefold longer than bolus clearing by Imp or manometry. In conclusion, impedance monitoring is better than manometry and pH monitoring in RE detection before and after a meal, and manometry in determining RE composition as liquid or gas. The pH probe measures RE acidity and acid clearing. Simultaneous impedance and pH combines the two methods strengths, and is a powerful tool for reflux detection and characterization.

Impedance monitoring (Imp) measures bolus transit. Combining Imp with manometry (EM) allows the effect of contractile patterns on transit to be assessed. The objective of this study is to identify bolus transit patterns in normal subjects, correlate Imp findings with the gold standard barium esophagram (Ba), and compare bolus transit with concomitant EM findings. Simultaneous Ba-Imp-EM was performed for 2 min in 15 normal volunteers (women, 11; age, 43 yr). Combined impedance-pressure sites were 5, 10, 15, 20 cm above the lower esophageal sphincter (LES). Boluses (10 ml) of 45% barium mixed with 0.9% NaCl were swallowed at > or = 20-s intervals (5-6 swallows/subject). Imp and Ba showed three bolus transit patterns, and the two methods were in agreement on the pattern type in 97% (83/86) of swallows. Normal bolus transit was found in 73% (61/83), and each had normal peristalsis and contraction amplitude. Stasis in the proximal esophagus occurred in 7 of 83 swallows despite normal manometric parameters in 4 of 7 swallows. Retrograde escape of a residue of incompletely cleared bolus from just above the LES to the site 5 cm above occurred in 14 of 83 swallows. Retrograde escape was triggered by the next swallow, occurred despite normal manometric parameters, and did not occur if the swallow interval was >30 s. In 55% (47/86) of swallows, air accumulated in the distal esophagus and persisted there for a mean of 3.6 s until cleared into the stomach. We conclude that impedance monitoring is a valid transit test and describe bolus transit patterns in normal subjects for comparison with patients with esophageal motility disorders.

Objectives: Impedance monitoring is a new diagnostic method for gastroesophageal reflux disease (GERD) where multiple impedance electrode pairs are placed on a standard pH catheter. It detects reflux of a liquid and/or gas bolus into the esophagus, as well as its distribution, composition, and clearing. The aim of this collaborative study is to define normal values for 24-h ambulatory simultaneous impedance and pH monitoring (24-h Imp-pH), and compare bolus parameters by impedance monitoring to changes in [H(+)] measured by pH monitoring., Methods: Sixty normal volunteers without GER symptoms underwent 24-h Imp-pH with impedance measured at six sites (centered at 3, 5, 7, 9, 15, and 17 cm above lower esophageal sphincter) and pH 5 cm above the LES. Reflux detected by impedance was characterized by the pH probe as either acid, weakly acidic, nonacid, or superimposed acid reflux. Proximal reflux was defined as reflux that reached the impedance site 15 cm above the LES., Results: Reflux frequency was common upright (median-27, 25th and 75th quartile-16, 42), but rare recumbent (median-1; 0, 4). A median of 34% (14%, 49%) of upright reflux reached the proximal esophagus. There was a similar number of mixed composition (liquid + gas; 49%) and liquid-only reflux (51%). Acid reflux was two-fold more common than weakly acidic reflux (p < 0.001). Superimposed acid reflux and nonacid reflux were rare. Acid neutralization to pH 4 took twice as long as volume clearance measured by impedance., Conclusions: Combining impedance and pH monitoring improves the detection and characterization of GER. This study characterizes the frequency, duration, and extent of reflux in health and provides normal values for 24-h Imp-pH for future comparison with GERD patients.