Relationship Between Pressure Wave Amplitude and Esophageal Bolus Clearance Assessed by Combined Manometry and Multichannel Intraluminal Impedance Measurement

OBJECTIVES: Esophageal wave amplitude is an important determinant of esophageal clearance. A threshold of 30 mmHg is widely accepted as the threshold for effective clearance in the distal esophagus. However, the precise relationship between wave amplitude and clearance has received relatively little attention. The aim of this study was to assess the impact of peristaltic wave amplitude on esophageal volume clearance using multiple intraluminal impedance (MII) measurement. METHODS: Concurrent manometry and MII were performed on 42 healthy asymptomatic volunteers and 13 patients with ineffective esophageal motility. Esophageal motility was measured at four sites 5-cm apart, starting 2 cm above the lower esophageal sphincter. MII was measured at corresponding sites with electrodes incorporated into the manometric assembly. Ten 5-mL liquid (saline) boluses and ten 5-mL low impedance viscous boluses were tested in each subject. Pressure wave amplitude was determined at each site as well as peristaltic success of the responses. Bolus clearance was measured from individual recording segment and from the esophagus as a whole. RESULTS: The proportion of liquid boluses cleared at each site was directly related to wave amplitude and did not increase significantly above a threshold of 25 mmHg in the proximal esophagus, 22 mmHg in the mid-esophagus, and 30 mmHg in the distal esophagus. Corresponding wave amplitudes for total esophageal clearance were 35-40 mmHg. There was a good correlation between the wave amplitude at one site of the esophagus and those of the rest of the esophagus. For both liquid and viscous boluses, the likelihood of impaired clearance was directly related to the number of segments with hypotensive pressure waves. CONCLUSION: The findings confirm the validity of the wave amplitude threshold required for effective liquid bolus clearance and have established the amplitude threshold for clearance of viscous boluses. However, the number of hypotensive pressure waves required for the definition of ineffective motility may be too low.