J Neurogastroenterol Motil 2024; 30(1): 46-53  https://doi.org/10.5056/jnm23057
Interpretation of Impedance Data on High-resolution Impedance Manometry Studies—A Worldwide Survey
Lev Dorfman,1* Sherief Mansi,1,2 Khalil El-Chammas,1,2 Chunyan Liu,3 and Ajay Kaul1,2
1Division of Gastroenterology, Hepatology, and Nutrition, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA; 2Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, USA; and 3Division of Biostatistics and Epidemiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
Correspondence to: *Lev Dorfman, MD
Division of Gastroenterology, Hepatology, and Nutrition, Cincinnati Children’s Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229, USA
Tel: +1-513-517-1070, E-mail: levdorfman@gmail.com
Received: April 19, 2023; Accepted: July 7, 2023; Published online: January 30, 2024
© The Korean Society of Neurogastroenterology and Motility. All rights reserved.

cc This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Background/Aims
Esophageal manometry is the gold standard for esophageal motility evaluation. High-resolution esophageal manometry with impedance (HRIM) allows concurrent assessment of bolus transit and manometry. Inconsistencies between concomitant impedance and manometry data pose a clinical dilemma and has not yet been addressed. We aim to assess interpretation trends of HRIM data among gastroenterologists worldwide.
Methods
A cross-sectional study using an anonymous survey was conducted among gastroenterologists worldwide. Statistical analysis was performed to compare responses between providers.
Results
We received responses from 107 gastroenterologists (26 countries). Most were adult providers (69, 64.5%), and most (77, 72.0%) had > 5 years of experience. Impedance was found to be helpful by 83 (77.6%) participants, but over 30% reported inconsistencies between impedance and manometry data. With incomplete bolus clearance and normal manometry 41 (38.7%) recommended observation, 41 (38.7%) recommended 24-hours pH-impedance, and 16 (15.1%) recommended prokinetics. With abnormal manometry and complete bolus clearance, 60 (57.1%) recommended observation while 18 (17.1%) recommended 24-hours pH impedance and 15 (14.3%) recommended prokinetics. A significant difference was found between providers from different continents in treating cases with discrepancy between impedance and manometry findings (P < 0.001). No significant differences were seen in responses between adult versus pediatric providers and between providers with different years of experience.
Conclusions
There is no consensus on interpreting HRIM data. Providers’ approaches to studies with inconsistencies between manometry and impedance data vary. There is an unmet need for guidelines on interpreting impedance data in HRIM studies.
Keywords: Esophageal manometry; High-resolution impedance manometry; Impedance; Manometry
Introduction

Dysphagia is a clinical manifestation of several disorders, and can have a major impact on quality of life of adult and pediatric populations.1,2 Evaluation and management of dysphagia dramatically changed with the introduction of esophageal manometry.3 Manometry studies use measurement of contraction pressures generated throughout the esophageal body during standardized swallow challenge and are considered the gold standard for the evaluation of esophageal motility patterns and disorders.4,5 Over the years, advances in esophageal manometry technology were facilitated with introduction of high-resolution esophageal manometry (HREM) and later, addition of impedance sensors to esophageal manometry catheters, allowing concurrent assessment of intrabolus pressure and bolus transit in relation to manometric changes (high-resolution impedance manometry [HRIM]).1,6,7 The clinical impact of the correlation between esophageal manometry parameters and bolus transit remains unclear,8 and is likely the reason that, impedance data has not been integrated into the most updated esophageal manometry interpretation guidelines––the Chicago classification version 4.0 (v4.0), published in 2021.9 Recently, several different novel pressure-impedance parameters were suggested for evaluation of patients with pharyngeal and esophageal motility disorders combining pressure and impedance data, and a dedicated commercial software was developed to assess bolus flow parameters.10-13

No consensus statements, systematic reviews or guidelines have been published to suggest optimal application of impedance data during HRIM in pediatric and adult populations. Inconsistencies in the interpretation of concomitant impedance and manometry data often pose a clinical dilemma with great variability in proposed management among different providers.

We aim to assess interpretation trends of HRIM data among pediatric and adult gastroenterologists worldwide by an anonymous survey, to assess their views on concomitant impedance and manometry data and to assess their opinion on the clinical utility of impedance information during HRIM studies.

Materials and Methods

We conducted a cross-sectional study based on a structured anonymous internet survey among practicing gastroenterologists worldwide from August 2022 to December 2022. The survey questionnaire was designed specifically for this study and included 10 questions assessing the implication of impedance data during esophageal manometry studies and proposed treatment strategies of the providers (Appendix). The survey was performed on Google Forms and distributed via professional organizations mailing lists. A comparison was performed between adult and pediatric gastroenterologists, between providers with less and more than 5 years of experience and between providers from different continents.

The term discrepancy for the purpose of this study, is used when manometry shows normal metrics while impedance shows abnormal bolus results, or vice versa.

Frequency and percentages were used to summarize the survey answers. Chi-square test or exact chi-square test (when the percentage of expected cell counts < 5 were more than 20%) was used to compare difference in the survey answers by the group variables of interest. The study was reviewed by the Cincinnati Children’s Hospital Institutional Review Board (IRB) and determined to be exempt from IRB review in accordance with applicable regulations and institutional policy (IRB No. 2022-0457).

Results

We received responses from 107 gastroenterologists in 26 countries. The survey answers were summarized by subspecialty, years of experience and continent. The overall distribution of the survey answers is listed in Table 1. Most of the responders were adult providers (69, 64.5%), and most (77, 72.0%) had more than 5 years of experience in gastroenterology. HREM impedance was found to be helpful by 83 (77.6%) responders, and over 30% reported frequent inconsistencies between impedance and manometry data. Inconsistency between manometry findings and impedance findings were often seen by 34 (31.8%) of responders, rarely seen by 71 (66.4%), and never seen by 2 (1.9%) responders.

Table 1 . Summary of Survey Answers

Survey questionnSurvey answerOverall (N = 107)
Do you find impedance data during esophageal manometry studies helpful?107
No2 (1.9%)
Sometimes22 (20.6%)
Yes83 (77.6%)
How often do you estimate that there is an inconsistency between manometry finding and impedance finding during esophageal manometry studies?107
Never2 (1.9%)
Often34 (31.8%)
Rarely71 (66.4%)
What would you do if a patient has normal esophageal manometry study with incomplete bolus clearance?106
Anti-reflux therapy2 (1.9%)
Observation only41 (38.7%)
Perform 24-hour pH-impedance study41 (38.7%)
Prokinetic medications16 (15.1%)
Repeat study6 (5.7%)
From your experience, does treatment with prokinetics improve symptoms of patients with normal esophageal manometry and incomplete bolus clearance?104
No70 (67.3%)
Yes34 (32.7%)
What would you do if a patient has abnormal esophageal manometry study with complete bolus clearance?105
Anti-reflux therapy7 (6.7%)
Observation only60 (57.1%)
Perform 24-hour pH-impedance study18 (17.1%)
Prokinetic medications15 (14.3%)
Repeat study5 (4.8%)
Would you treat a patient with normal manometry study except for incomplete bolus clearance by impedance with paste/solids only?102
Based on symptoms13 (12.7%)
No34 (33.3%)
Only if the esophageal manometry findings are abnormal37 (36.3%)
Yes17 (16.7%)
Other-perform further testing (esophagram)1 (1.0%)
Do you address the impedance during multiple rapid swallow test?107
No40 (37.4%)
Yes67 (62.6%)


With incomplete clearance and normal pressure manometry metrics, an equal number of 41 (38.7%) responders recommended observation or 24-hours pH-impedance study, an additional 16 (15.1%) recommended treatment with prokinetics and 6 (5.7%) recommended repeating the study (Figure). More than two-thirds of providers stated that from their experience, prokinetics did not help in such circumstances. For patients who had normal pressure manometry metrics and incomplete bolus clearance for only paste/solid swallows, most of the responders (71, 69.6%) stated that they would not provide treatment, while 17 (16.7%) recommended treating patients with such findings. An additional 13 (12.7%) recommended symptom-based treatment and 1 (1.0%) recommended performing an esophagram.

Figure 1. Participant’s work-up plan in cases of discrepancy between manometry and impedance data.

On the contrary, with abnormal esophageal metrics on HREM and complete bolus clearance by impedance, most responders (60, 57.1%) recommended observation while 18 (17.1%) recommended performing 24-hours pH impedance study and an additional 15 (14.3%) recommended treatment with prokinetics. Anti-reflux therapy was recommended by 7 (6.7%) and 5 (4.8%) recommended repeating HREM.

Forty (37.4%) responders stated that they did not address impedance findings during multiple rapid swallow test.

A significant difference was found between providers from different continents in treating cases with discrepancy between impedance and HREM findings (P < 0.001, Table 2).

Table 2 . Summary of Survey Answers by 5 Continents

Survey questionnSurvey answerAsia
(n = 6)
Europe
(n = 18)
North America
(n = 64)
Oceania
(n = 9)
South America
(n = 10)
P-value
1. Do you find pH impedance data during esophageal manometry studies helpful?1070.693
No0 (0.0%)0 (0.0%)1 (1.6%)1 (11.1%)0 (0.0%)
Sometimes1 (16.7%)3 (16.7%)14 (21.9%)2 (22.2%)2 (20.0%)
Yes5 (83.3%)15 (83.3%)49 (76.6%)6 (66.7%)8 (80.0%)
2. How often do you estimate that there is an inconsistency between manometry finding and impedance finding during esophageal manometry studies?1070.204
Never0 (0.0%)0 (0.0%)0 (0.0%)1 (11.1%)1 (10.0%)
Often2 (33.3%)4 (22.2%)23 (35.9%)3 (33.3%)2 (20.0%)
Rarely4 (66.7%)14 (77.8%)41 (64.1%)5 (55.6%)7 (70.0%)
3. What would you do if a patient has normal esophageal manometry study with incomplete bolus clearance?106< 0.001
Anti-reflux therapy0 (0.0%)0 (0.0%)2 (3.1%)0 (0.0%)0 (0.0%)
Observation only1 (16.7%)4 (22.2%)28 (43.8%)4 (50.0%)4 (40.0%)
Perform 24-hour pH-impedance study2 (33.3%)11 (61.1%)23 (35.9%)1 (12.5%)4 (40.0%)
Prokinetic medications2 (33.3%)1 (5.6%)10 (15.6%)2 (25.0%)1 (10.0%)
Repeat study1 (16.7%)2 (11.1%)1 (1.6%)1 (12.5%)1 (10.0%)
4. From your experience, does treatment with prokinetics improve symptoms of patients with normal esophageal manometry and incomplete bolus clearance?1040.799
No3 (50.0%)12 (75.0%)42 (65.6%)7 (77.8%)6 (66.7%)
Yes3 (50.0%)4 (25.0%)22 (34.4%)2 (22.2%)3 (33.3%)
5. What would you do if a patient has abnormal esophageal manometry study with complete bolus clearance?105< 0.001
Anti-reflux therapy0 (0.0%)1 (5.9%)6 (9.4%)0 (0.0%)0 (0.0%)
Observation only4 (66.7%)11 (64.7%)34 (53.1%)7 (87.5%)4 (40.0%)
Perform 24-hour pH-impedance study0 (0.0%)4 (23.5%)11 (17.2%)0 (0.0%)3 (30.0%)
Prokinetic medications2 (33.3%)0 (0.0%)12 (18.8%)1 (12.5%)0 (0.0%)
Repeat study0 (0.0%)1 (5.9%)1 (1.6%)0 (0.0%)3 (30.0%)
6. Would you treat a patient with normal manometry study except for incomplete bolus clearance by impedance with paste/solids only?102< 0.001
Based on symptoms0 (0.0%)2 (13.3%)7 (11.3%)3 (33.3%)1 (10.0%)
No0 (0.0%)7 (46.7%)22 (35.5%)4 (44.4%)1 (10.0%)
Only if the esophageal manometry findings are abnormal4 (66.7%)3 (20.0%)24 (38.7%)1 (11.1%)5 (50.0%)
Yes2 (33.3%)3 (20.0%)9 (14.5%)1 (11.1%)2 (20.0%)
Other-perform further testing (esophagram)0 (0.0%)0 (0.0%)0 (0.0%)0 (0.0%)1 (10.0%)
7. Do you address the impedance during multiple rapid swallow test?1070.893
No2 (33.3%)7 (38.9%)22 (34.4%)4 (44.4%)5 (50.0%)
Yes4 (66.7%)11 (61.1%)42 (65.6%)5 (55.6%)5 (50.0%)


A trend was noted among pediatric gastroenterologists who seemed to notice inconsistencies between manometry findings and impedance findings more often than adult providers (44.7% vs 24.6%, P = 0.052).

No significant differences were seen between responders based on their years of professional experience.

Discussion

This is the first study to assess current clinical practice and providers opinions regarding the added value of impedance during HREM studies and their approach in cases of discordance between manometry and impedance findings. In our survey we found that more than 20% of responders find impedance data to be sometimes helpful, and almost one-third report inconsistency between manometry metrics and impedance results.

A higher percentage of pediatric providers reported discrepancy between manometric and impedance findings (44.7% vs 24.6%), and this may reflect the use of adult norm values in interpretation of HREM metrics in pediatric patients. It was previously shown that esophageal length has an impact on HREM metrics, and lack of pediatric norm values may cause over diagnosis of esophageal motility disorders.14,15 While interpretation of concomitant impedance data along with HREM metrics has not been addressed in the Chicago classification for adults, addition of impedance to HREM studies is mentioned in the pediatric consensus document published by the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition and the American Neurogastroenterology and Motility Society.16 This consensus statement specifies clinical settings in which addition of impedance might change the clinical management, but unfortunately, there are no guidelines suggesting evaluation and treatment strategies in cases of discrepancy between HREM metrics and bolus clearance on impedance. Incomplete bolus clearance was recently described in almost 50% of adult patients with normal motility on HREM, but management guidelines were not suggested.17 A combination of incomplete bolus clearance and normal HREM metrics, does not fulfill the criteria for ineffective esophageal motility (IEM) and would be classified as normal by Chicago classification v4.0. These gaps in classification underscore the need to address bolus clearance results in current guidelines, including standardized definition of complete and incomplete bolus clearance.18-20 Between HREM metrics and bolus clearance, the latter represent a more physiologic measure. A stepwise approach starting with assessment of bolus clearance and followed by analysis of HREM metrics only in cases of abnormal bolus clearance, could be considered.

Lack of consensus statements and guidelines relating to standard of care for managing patients with conflicting findings, is reflected in the variability in suggested management of a patient with normal HREM metrics and incomplete bolus clearance which ranges from observation to performing further diagnostic studies and trial of prokinetic medications. Furthermore, a third of the responders suggest treatment with prokinetics while two thirds of them state that from their experience treatment with prokinetics is not likely to be beneficial.

A significant difference was noted among responders from different continents in addressing equivocal cases with discrepancy between HREM and impedance data with higher proportion of responders suggesting repeating the study in Asia and South America and less treatment with prokinetics. Such differences might reflect variability in healthcare systems, cultural practices, and economic status. Considering the lack of evidence-based data in both children and adults, and an absence of international societal guidelines, these findings provide us with a concerning understanding of the widely different practice across providers worldwide.

Absence of contraction reserve on multiple rapid swallow was previously described to be associated with incomplete bolus clearance.21 Recently performance of multiple rapid swallow in conjunction with bolus clearance data evaluated by impedance was shown to be beneficial in challenging cases of IEM.17 In our survey, more than one-third of responders stated that they do not take into account impedance findings during this maneuver. The diagnosis of IEM is still evolving with a growing number of publications in literature suggesting additional diagnostic modalities to the previously defined IEM criteria by Chicago classification v4.0.17,22,23 The role of incomplete bolus clearance in this definition is yet to be determined.

Our survey results demonstrate an urgent unmet need in the development of evidence-based approach with standardization of interpretation of HRIM studies both in adults and children. Since technology is already available world-wide, it is now imperative that we focus on supporting studies aiming to acquire valuable data from well-designed, multi-center studies including children and adults. In the meantime, an expert consensus statement might address the need for a standardized approach which will avoid individual-experience based practice and allow further research and standardization of interpretation and treatment.

Our study has some limitations including being an anonymous, internet-based survey, which lacks the ability to assess the reliability of the responses or the practices of the respondents. In addition, different centers use different manometry and impedance systems and catheters, which may impact their experience and interpretation. We did not cover the latest impedance metrics such as bolus presence time and trans-esophagogastric junction-bolus flow that are currently utilized in some centers to ensure the survey represents the most prevalent clinical observations and to prevent restricting it to a few referral centers only.

Our study provides valuable information regarding the utility of esophageal impedance data during HRIM studies, its impact on clinical decision making and the ability to compare the differences in clinical practice between adult and pediatric providers.

In conclusion, the survey reveals significant knowledge gaps and clinical practice variability in the diagnosis and treatment of esophageal motility disorders. These discrepancies can be attributed to the absence of standardized definitions of norms, particularly when combining manometry with impedance data. Additionally, pediatric gastroenterologists encounter more obstacles, as there are no established norms for pediatric esophageal manometry in standard practice. Further research is necessary to develop guidelines that can promote standardization of diagnosis and facilitate evidence-based treatment for our patients. Our findings emphasize the need for further research and guidelines to establish the place of impedance during HRIM studies and its’ effect on clinical management of adult and pediatric patients with dysphagia.

Financial support

None.

Conflicts of interest

None.

Author contributions

Lev Dorfman, Sherief Mansi, Khalil El-Chammas, and Ajay Kaul conceptualized and designed the study, and drafted the manuscript; Lev Dorfman and Sherief Mansi participated in acquisition of data and analysis and interpretation of data; and Chunyan Liu participated in study design and performed data analysis. All the authors critically revised the manuscript and approved the final version.

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