High-resolution impedance manometry parameters enhance the esophageal motility evaluation in non-obstructive dysphagia patients without a major Chicago Classification motility disorder

Abstract

Background: High-resolution impedance manometry (HRIM) allows evaluation of esophageal bolus retention, flow, and pressurization. We aimed to perform a collaborative analysis of HRIM metrics to evaluate patients with non-obstructive dysphagia.

Methods: Fourteen asymptomatic controls (58% female; ages 20-50) and 41 patients (63% female; ages 24-82), 18 evaluated for dysphagia and 23 for reflux (non-dysphagia patients), with esophageal motility diagnoses of normal motility or ineffective esophageal motility, were evaluated with HRIM and a global dysphagia symptom score (Brief Esophageal Dysphagia Questionnaire). HRIM was analyzed to assess Chicago Classification metrics, automated pressure-flow metrics, the esophageal impedance integral (EII) ratio, and the bolus flow time (BFT).

Key results: Significant symptom-metric correlations were detected only with basal EGJ pressure, EII ratio, and BFT. The EII ratio, BFT, and impedance ratio differed between controls and dysphagia patients, while the EII ratio in the upright position was the only measure that differentiated dysphagia from non-dysphagia patients.

Conclusions & inferences: The EII ratio and BFT appear to offer an improved diagnostic evaluation in patients with non-obstructive dysphagia without a major esophageal motility disorder. Bolus retention as measured with the EII ratio appears to carry the strongest association with dysphagia, and thus may aid in the characterization of symptomatic patients with otherwise normal manometry.

Keywords: dysphagia; esophageal motility; high-resolution manometry; impedance.

Figure 1. The esophageal impedance integral (EII) ratio

A) The pressure topography plot of a normal, single swallow from a dysphagia patient is displayed. The region-of-interest for the EII ratio is designated with the red-dashed box. The black-dashed box is displayed in Figure 2 for generation of the bolus flow time. B) Areas of bolus presence are enclosed within the white lines. The EII ratio was calculated as the measured bolus volume (impedance pixel-density within areas of bolus presence) in Z2, the post-swallow-EII, divided by the bolus volume in Z1, the swallow-EII (C). The displayed swallow yielded a normal EII-ratio of 0.2. Figure used with permission from the Esophageal Center at Northwestern.

Figure 1. The esophageal impedance integral (EII) ratio

A) The pressure topography plot of a normal, single swallow from a dysphagia patient is displayed. The region-of-interest for the EII ratio is designated with the red-dashed box. The black-dashed box is displayed in Figure 2 for generation of the bolus flow time. B) Areas of bolus presence are enclosed within the white lines. The EII ratio was calculated as the measured bolus volume (impedance pixel-density within areas of bolus presence) in Z2, the post-swallow-EII, divided by the bolus volume in Z1, the swallow-EII (C). The displayed swallow yielded a normal EII-ratio of 0.2. Figure used with permission from the Esophageal Center at Northwestern.

Figure 1. The esophageal impedance integral (EII) ratio

A) The pressure topography plot of a normal, single swallow from a dysphagia patient is displayed. The region-of-interest for the EII ratio is designated with the red-dashed box. The black-dashed box is displayed in Figure 2 for generation of the bolus flow time. B) Areas of bolus presence are enclosed within the white lines. The EII ratio was calculated as the measured bolus volume (impedance pixel-density within areas of bolus presence) in Z2, the post-swallow-EII, divided by the bolus volume in Z1, the swallow-EII (C). The displayed swallow yielded a normal EII-ratio of 0.2. Figure used with permission from the Esophageal Center at Northwestern.

Figure 2. Pressure Flow Analysis

A. Pressure topography plot of a 5-ml saline swallow from a control subject showing the two regions of interest (ROI) used; ROI 1 from upper esophageal spincter (UES) to esophago-gastric junction (EGJ) and RO2 from transition zone (TZ) to EGJ. B. Pressure isocontour plot of ROI 1 showing the time and position of nadir impedance, indicating timing of bolus distension, and peak pressure, indicating maximum contraction. Plots right show impedance values mapped to these locations and the impedance ratio (calculated as nadir impedance/peak pressure impedance). Average values along ROI 1 were determined for each swallow. C. Pressure-impedance plot derived at sensor position number 14. Pressure (black line) and impedance (purple line) are shown for a 12s period from from swallow onset (0s). Note that impedance values have been reversed (lowest impedance at the top) for ease of presentation. This is a representative example showing how four key pressure-flow variables were calculated, these were; pressure at nadir impedance (1.PNI) representing the pressure at maximum luminal distension, intrabolus pressure (2.IBP) and intrabolus pressure slope (3.IBP slope), representing the median pressure and gradient of pressure change respectively during luminal closure (defined by the period from nadir impedance to the midpoint between nadir impedance and peak pressure), and the time from nadir impedance to peak pressure (4.TNIPP) representing the latency period from maximum distension to maximum contraction. D. Plots of the four key pressure variables and the pressure-flow index composite score based on values which were calculated at all axial locations along ROI 2 (using the operations shown in C). Average values along ROI 2 were determined for each swallow. Note the marked increase in bolus pressurisation and shortening of distention-contraction latency below sensor position number 18. This correspondes to an increase in bolus flow resistance associated with the transiton from compartmentalised bolus transport along the esophagus to esophageal emptying across a (variably resistive) EGJ opening.

Figure 3. Bolus flow time (BFT)

The top panel is the esophageal pressure topography of the distal esophagus; the overlaid horizontal lines represent the placement of the EGJ and gastric impedance and manometry signals. The middle panel represents the impedance signals which were used to determine the time of bolus presence. The bottom panel represents the pressure signals used to determine periods of a flow-permissive pressure gradient, i.e. when the esophageal pressure, red line, was greater than both the hiatal (crural diaphragm, CD) and intra-gastric pressure signals. The BFT was then derived as the time when both criteria (1. bolus presence and 2. trans-EGJ flow permissive pressure gradient) were met. Figure used with permission from the Esophageal Center at Northwestern.

Figure 4. Comparison of high-resolution impedance manometry (HRIM) metrics

Standard supine HRM metrics (A), supine HRIM metrics (B), and upright HRIM metrics (C) were compared across subject groups. † = p-value < 0.017 compared with controls. ‡ = p-value < 0.017 compared with dysphagia patients. Outliers omitted from the charts for display purposes are indicated with arrows. IRP – integrated relaxation pressure. DCI – distal contractile integral. EGJP – esophagogastric junction pressure. EII – esophageal impedance integral. PNI – pressure at nadir impedance. IBP – intrabolus pressure. TNIPP – time from nadir impedance to peak pressure.

Figure 4. Comparison of high-resolution impedance manometry (HRIM) metrics

Standard supine HRM metrics (A), supine HRIM metrics (B), and upright HRIM metrics (C) were compared across subject groups. † = p-value < 0.017 compared with controls. ‡ = p-value < 0.017 compared with dysphagia patients. Outliers omitted from the charts for display purposes are indicated with arrows. IRP – integrated relaxation pressure. DCI – distal contractile integral. EGJP – esophagogastric junction pressure. EII – esophageal impedance integral. PNI – pressure at nadir impedance. IBP – intrabolus pressure. TNIPP – time from nadir impedance to peak pressure.

Figure 4. Comparison of high-resolution impedance manometry (HRIM) metrics

Standard supine HRM metrics (A), supine HRIM metrics (B), and upright HRIM metrics (C) were compared across subject groups. † = p-value < 0.017 compared with controls. ‡ = p-value < 0.017 compared with dysphagia patients. Outliers omitted from the charts for display purposes are indicated with arrows. IRP – integrated relaxation pressure. DCI – distal contractile integral. EGJP – esophagogastric junction pressure. EII – esophageal impedance integral. PNI – pressure at nadir impedance. IBP – intrabolus pressure. TNIPP – time from nadir impedance to peak pressure.