Flow time through esophagogastric junction derived during high-resolution impedance-manometry studies: a novel parameter for assessing esophageal bolus transit

Abstract

This study aimed to develop and validate a method to measure bolus flow time (BFT) through the esophagogastric junction (EGJ) using a high-resolution impedance-manometry (HRIM) sleeve. Ten healthy subjects were studied with concurrent HRIM and videofluoroscopy; another 15 controls were studied with HRIM alone. HRIM studies were performed using a 4.2-mm-outer diameter assembly with 36 pressure sensors at 1-cm intervals and 18 impedance segments at 2-cm intervals (Given Imaging, Los Angeles, CA). HRIM and fluoroscopic data from four barium swallows, two in the supine and two in the upright position, were analyzed to create a customized MATLAB program to calculate BFT using a HRIM sleeve comprising three sensors positioned at the crural diaphragm. Bolus transit through the EGJ measured during blinded review of fluoroscopy was almost identical to BFT calculated with the HRIM sleeve, with the nadir impedance deflection point used as the signature of bolus presence. Good correlation existed between videofluoroscopy for measurement of upper sphincter relaxation to beginning of flow [R = 0.97, P < 0.001 (supine) and R = 0.77, P < 0.01 (upright)] and time to end of flow [R = 0.95, P < 0.001 (supine) and R = 0.82, P < 0.01 (upright)]. The medians and interquartile ranges (IQR) of flow time though the EGJ in 15 healthy subjects calculated using the virtual sleeve were 3.5 s (IQR 2.3-3.9 s) in the supine position and 3.2 s (IQR 2.3-3.6 s) in the upright position. BFT is a new metric that provides important information about bolus transit through the EGJ. An assessment of BFT will determine when the EGJ is open and will also provide a useful method to accurately assess trans-EGJ pressure gradients during flow.

Keywords: bolus transit; impedance; manometry.

Fig. 1.

Methodology for analyzing impedance and manometric correlates of bolus transit through the esophagogastric junction (EGJ). A: esophageal pressure topography (EPT) of a single swallow with overlaid impedance traces through the EGJ from sensors 31–33 [high-resolution impedance manometry (HRIM) sleeve], with the corresponding impedance values (kΩ) shown as white numerals. B: pressure traces through the HRIM sleeve at sensors 31–33. Simultaneous fluoroscopic images are from the times shown as white circles on the impedance trace in A, positioned at the crural diaphragm on the EPT plot, and the lines extending from the circles onto the manometric panel. Time points of interest (i, ii, and iii) are documented at the top of the EPT plot (A), and areas of flow are shown as horizontal pink bars (B). This layout provides an opportunity to visualize impedance and manometry correlates of bolus presence and transit during a single swallow. At baseline, resting EGJ pressure is 25 mmHg and impedance is 2.2 kΩ. Impedance does not change dramatically after upper esophageal sphincter relaxation (i), and flow does not occur until the point shown by the black circle, when impedance reaches its nadir deflection (0.26 kΩ) and a preferential pressure gradient is noted through the EGJ into the stomach. There is no evidence of flow during the impedance drop at the 50% mark (1.1 kΩ), and this correlates with EGJ relaxation. Flow stops during the crural contraction (blue pressure trace), where peak contractions are 27 and 26 mmHg. This shift of the crural diaphragm signal among the sensors is consistent with typical axial sensor changes during swallowing. Flow continues after the crural contraction returns to baseline pressure.

Fig. 2.

Methodology for derivation of trans-EGJ bolus flow time (BFT) from HRIM data. A: EGJ region of interest on an EPT plot centered on the EGJ. B and C: 3 impedance traces (B) and 3 pressure traces (C) from HRIM data beginning 2 s before upper esophageal sphincter relaxation used to identify bolus presence in the distal esophagus (black dashed lines) and BFT (black solid lines). Horizontal pink bars represent times of flow visualized on fluoroscopy. These times are closely synchronized with BFT domains. CD, crural diaphragm.