Evaluation of esophageal distensibility in eosinophilic esophagitis: an update and comparison of functional lumen imaging probe analytic methods

Abstract

Background: Distensibility evaluation of the esophageal body using the functional lumen imaging probe (FLIP) offers an objective measure to characterize patients with eosinophilic esophagitis (EoE), though this analysis may be limited by unrecognized catheter movement and esophageal contractility. The aims of this study were to report novel FLIP analytic methods of esophageal distensibility measurement in EoE and to assess the effect of contractility.

Methods: Nine healthy controls (six female; ages 20-49) and 20 EoE patients (four female; ages 19-64; grouped by degree of distension-mediated contractility identified on FLIP) were evaluated with a 16-cm FLIP device during step-wise balloon distension during upper endoscopy. A distensibility plateau (DP) was generated using multiple methods to identify the narrowest esophageal body diameter: (i) wavelet decomposition (WD), (ii) maximal diameter (MD), and (iii) FLIP Analytics software.

Key results: Distensibility was reduced in EoE patients compared with controls using the WD (p = 0.002) and MD (p = 0.001) methods; a trend was detected using the FLIP Analytics method (p = 0.055). Significant intra-subject differences were detected between methods among both patients and controls (p-values <0.001 to 0.025); the difference was more pronounced among subjects with a greater degree of contractility. DP was <19 mm among 7/9 controls with FLIP Analytics, 6/9 controls with WD, and 0/9 controls using the MD method.

Conclusions & inferences: Distension-mediated contractility affects distensibility measurement with the FLIP. Using software-based algorithms, particularly with a method that identifies the maximal-achieved diameters (MD), may improve objective distensibility measurement for clinical research and practice.

Keywords: eosinophilic esophagitis; functional lumen imaging probe; impedance planimetry.

© 2016 John Wiley & Sons Ltd.

Figures

Figure 1. FLIP Topography plots

Examples of EoE patients with repetitive, antegrade contractions (RACs) (A) and without RACs (B) are displayed. The topographic plots (top-panels) represent color-coded diameter-plots generated from interpolation of the impedance-planimetry data by spatial orientation (y-axis) by time (x-axis). The 8-cm of the topographic plot above the white line, which represents 3-cm above the EGJ midline, was subjected to analysis of esophageal body distensibility. The intra-balloon pressure (blue line) and the volumetric distension protocol (black line) are represented in the bottom panels. The nadir pressures identified at each distension volume (black dots) were utilized to create distensibility plots. Notably, the distension protocol in A only extended to 40-ml, likely related to the contraction-associated pressure peaks of > 60-mmHg, while the distension protocol in B was able to extend to a 60-ml fill volume.

Figure 2. Wavelet decomposition

Diameter measures after wavelet decomposition (blue lines) are overlaid on the original diameter data (red) for the 8-cm of impedance planimetry data within the esophageal body for the same EoE patients displayed in Figure 1. The greater overall degree of filtering, i.e. change in analyzed diameters, in the patients with repetitive, antegrade contractions (RACs) (A) compared to the patient without RACs (B) can be appreciated.

Figure 3. Distensibility plateau (DP)

The data points represent the corresponding narrowest diameter, identified using the wavelet decomposition (WD)-method (circles), and maximal diameter (MD)-method (squares), and nadir intra-balloon pressures that were identified at each 5-ml step-wise distension volume. The DP was calculated based on the plotted polynomial curve. Examples from the same two EoE patients as Figures 1-2 with (A) and without (B) repetitive, antegrade contractions (RACs), as well as two control subjects (red), one with (A) and one without RACs (B), are displayed. The difference between methods among subjects with RACs (A) can be appreciated, while in those subjects without RACs (B), the WD and MD-DP plots are nearly super-imposed.

Figure 4. The 40-mmHg restricting diameter (RD) and luminal volume (LV)

Examples from the same two EoE patients and same two controls (red) as Figure 3 with (A) and without (B) repetitive, antegrade contractions (RACs) are displayed. The narrowest diameter along the spatial variation plot (purple circles) were identified as the RD. The area-under-the-curve (purple for the EoE patients) was transformed to generate the 40LV.

Figure 5. Flip Analytics – distensibility plateau (DP)

Examples from the same two EoE patients with (A) and without (B) RACs are displayed; DPs were 11.4 mm (evaluation of the top channel was omitted) (A) and 10.3 mm (B).

Figure 5. Flip Analytics – distensibility plateau (DP)

Examples from the same two EoE patients with (A) and without (B) RACs are displayed; DPs were 11.4 mm (evaluation of the top channel was omitted) (A) and 10.3 mm (B).

Figure 6. Intra-subject comparison of distensibility plateau analytic methods

Distensibility plateau measures from each subject (A. Controls, B. EoE patients with repetitive, antegrade contractions (RACs), and C. EoE patients without RACs) are represented across analysis methods. A lesser degree of intra-subject variation was observed among subjects without RACs, which are represented with white squares; circles indicate subjects with RACs.

Figure 6. Intra-subject comparison of distensibility plateau analytic methods

Distensibility plateau measures from each subject (A. Controls, B. EoE patients with repetitive, antegrade contractions (RACs), and C. EoE patients without RACs) are represented across analysis methods. A lesser degree of intra-subject variation was observed among subjects without RACs, which are represented with white squares; circles indicate subjects with RACs.

Figure 6. Intra-subject comparison of distensibility plateau analytic methods

Distensibility plateau measures from each subject (A. Controls, B. EoE patients with repetitive, antegrade contractions (RACs), and C. EoE patients without RACs) are represented across analysis methods. A lesser degree of intra-subject variation was observed among subjects without RACs, which are represented with white squares; circles indicate subjects with RACs.