855 Measurement of Esophagogastric Junction Distensibility Identifies a Subgroup of Achalasia Patients With Manometrically Normal LES Relaxation

to have impedance recording sites spaced 2 cm apart and positioned through the EGJ and UES. The two techniques used to measure the IBH utilize the nadir impedance to highlight the liquid to mucosa/air interface using the impedance color topography contour plot and the spatial impedance variation plot. The impedance topography method utilizes a smart mouse tool to measure the distance from the proximal aspect of the EGJ to the top of the topographic color change during end-expiration. The spatial impedance variation plot presents the instantaneous impedance change along the axial length of the esophagus. Interpolation is utilized to smooth out the curve and the range for the impedance measure is set at the nadir impedance to delineate the inflection point where the liquid interface occurs. The IBH is measured as the location along the catheter where the nadir impedance inflection occurs to signify the top of the bolus.