Tu1980 Radiological Correlates of Esophageal Pressure-Flow Variables Derived by Automated Impedance Manometry (AIM) Analysis

INTRODUCTION: Pressure-flow analysis may quantify the interactions between bolus transport and pressure generation during bolus swallowing. The functional relevance of pressure flow metrics is still to be fully elucidated and therefore we undertook a pilot study to assess the interrelationships between pressure-flow metrics and fluoroscopically determined bolus clearance and bolus transport across the EGJ. We hypothesise that differences in pressureflow metrics would correlate with changes in bolus clearance and reduced flow across the EGJ. METHODS: Videofluoroscopic images, impedance and pressure were recorded simultaneously in 16 control subjects (19-44y, 8m) tested with liquid (L), semi-solid (SS) and solid barium boluses (S). A 3.6mm diameter solid-state catheter with 36x1cm pressure/ 16x2cm impedance was used (Solar GI system, MMS). Swallowed bolus clearance was videofluroscopically assessed using a validated 7-point bolus transport scale; higher score = poor bolus clearance. The cumulative period of bolus flow across the EGJ was also measured (EGJ flow time). Pressure Flow Index (PFI) was used to integrate bolus pressurisation and flow timing and Impedance Ratio (IR) was used to assess the effectiveness of bolus clearance. Subjects were asked to report the level of perception of bolus transit using a 5 point scale. RESULTS: in total 92 swallows were simultaneously acquired. A higher transport score, indicating more severe levels of bolus transport failure, correlated with higher Impedance Ratios (L r = 0.617 p<0.001; SS r= 0.580 p<0.001; S 0.841 p<0.001). IR had strong prognostic value for detecting incomplete bolus clearance (ROC area for transport score ≥3 was L 0.902; SS 0.782; S 0.906). When subjects perceived bolus transit this was associated with a higher bolus transport score (2.0 vs. 4.6 for perception score 1 vs. score 2-5 respectively p=0.04). PFI and IR were used in combination to distinguish individual swallows on grounds of abnormal bolus pressurisation and/or clearance. Figure A demonstrates how solid swallows could be separated into 3 groups based on high or low PFI/IR : Group 1 Low PFI/ low IR, Group 2 low PFI /high IR and Group 3 high PFI. Comparisons among these groups in relation to fluoroscopic measures shows bolus transport abnormalities in Group 2 only (Fig B). EGJ flow time was shortest in Group 3 (Fig C). CONCLUSIONS: Different pressureflow signatures are associated with altered bolus clearance and/or flow across the EGJ. A high PFI pattern is associated with diminished flow across the EGJ, possibly due to increased flow resistance in the distal esophagus whilst a high IR is consistent with failed bolus transport to the EGJ. This study provides radiological confirmation that patterns of abnormal PFI and/or IR in dysphagia patients are consistent with abnormal flow patterns, possibly explaining patient symptoms.