Measurement of Esophageal Nocturnal Baseline Impedance: A Simplified Method

Utility of mean nocturnal baseline impedance and post-reflux swallow-induced peristaltic wave index in clinical pH-impedance reflux study

BACKGROUND AND AIMS

Analysis of mean nocturnal baseline impedance (MNBI) and post-reflux swallow-induced peristaltic wave index (PSPWi) have been proposed to increase the diagnostic yield of pH-impedance studies in reflux disease. However, routine use of these indices in clinical studies is yet to be established, particularly with PSPWi, which requires laborious manual analysis. Our study aimed to assess the utility of MNBI and PSPWi and their potential for future incorporation into clinical practice.

METHODS

pH-impedance recordings from consecutive patients referred to the Motility Laboratory at Royal Adelaide Hospital for evaluation of gastro-oesophageal reflux disease (GORD) were prospectively collected and manually analysed. Baseline demographic characteristics, symptoms, acid exposure time (AET), number of reflux episodes, and MNBI and PSPWi were collected.

RESULTS

Eighty-nine patients were included in the study (age 50 ± 17 years, 35 males). MNBI and PSPWi inversely correlated with AET (R = -0.678, P < 0.0001 and R = -0.460, P < 0.0001 respectively) and with reflux episodes (R = -0.391, P = 0.0002 and R = -0.305, P = 0.0037 respectively). In patients with a negative pH study, but with typical reflux symptoms, 4/30 (13%) had pathologic MNBI and PSPWi. There was a positive correlation between MNBI and PSPWi values (R = 0.525, P < 0.0001). Performing analysis of PSPWi was substantially more laborious than MNBI.

CONCLUSION

MNBI and PSPWi are both useful adjuncts in the diagnosis of reflux disease, although in our cohort MNBI showed stronger correlation with AET with less time to analyse. The role of these indices remains to be further explored, particularly in patients with inconclusive AET and in those with positive compared to negative symptom association.

Does severe and chronic esophageal distension by air (observed in SGB and GB) affect the esophageal mucosa integrity (MNBI)

BACKGROUND

Supragastric belching (SGB) and aerophagia are behavioral disorders characterized by air induced esophageal distension. SGB is known to be associated with Gastro Esophageal Reflux Disease (GERD). Low Mean Nocturnal Baseline Impedance (MNBI) values support GERD diagnosis. We aimed to assess if chronic esophageal distension by air affects the esophageal mucosa integrity by assessing changes in MNBI.

METHODS

In a single-center database study, we searched retrospectively for patients with a diagnosis of pathological SGB (n = 146) or aerophagia (n = 34) based on impedance-pH reflux monitoring. During the examined period, patients with a conclusive negative diagnosis of SGB and no evidence of aerophagia were used as a control cohort (n = 191). MNBI at 3, 5, and 17 cm over Lower Esophageal Sphincter (LES) was evaluated. GERD was diagnosed if acid exposure time (AET) >6%. All impedance studies of included patients were prospectively reevaluated.

RESULTS

GERD was diagnosed in 31.7% patients with SGB, a rate not different in comparison to patients without SGB (30.8%, p = 0.906). MNBI at 3 and 5 cm above the LES was significantly decreased among patients with SGB. SGB was not correlated with MNBI at 3 cm over the LES, (p: 0.086 OR: 1.000 95% CI: 0.999-1.001) when using multivariate analysis. Moreover no difference was spotted as far as MNBI at 3, 5, and 17 cm over the LES is concerned among patients with or without aerophagia.

CONCLUSION

Even if patients with SGB do show lower MNBI values, esophageal distention due to excessive air movement does not directly lead to impairment of esophageal mucosa integrity.

Latin American consensus on diagnosis of gastroesophageal reflux disease

BACKGROUND

Diagnosing gastroesophageal reflux disease (GERD) can be challenging given varying symptom presentations, and complex multifactorial pathophysiology. The gold standard for GERD diagnosis is esophageal acid exposure time (AET) measured by pH-metry. A variety of additional diagnostic tools are available. The goal of this consensus was to assess the individual merits of GERD diagnostic tools based on current evidence, and provide consensus recommendations following discussion and voting by experts.

METHODS

This consensus was developed by 15 experts from nine countries, based on a systematic search of the literature, using GRADE (grading of recommendations, assessment, development and evaluation) methodology to assess the quality and strength of the evidence, and provide recommendations regarding the diagnostic utility of different GERD diagnosis tools, using AET as the reference standard.

KEY RESULTS

A proton pump inhibitor (PPI) trial is appropriate for patients with heartburn and no alarm symptoms, but nor for patients with regurgitation, chest pain, or extraesophageal presentations. Severe erosive esophagitis and abnormal reflux monitoring off PPI are clearly indicative of GERD. Esophagram, esophageal biopsies, laryngoscopy, and pharyngeal pH monitoring are not recommended to diagnose GERD. Patients with PPI-refractory symptoms and normal endoscopy require reflux monitoring by pH or pH-impedance to confirm or exclude GERD, and identify treatment failure mechanisms. GERD confounders need to be considered in some patients, pH-impedance can identify supragrastric belching, impedance-manometry can diagnose rumination.

CONCLUSIONS

Erosive esophagitis on endoscopy and abnormal pH or pH-impedance monitoring are the most appropriate methods to establish a diagnosis of GERD. Other tools may add useful complementary information.

Updates to the modern diagnosis of GERD: Lyon consensus 2.0

The Lyon Consensus provides conclusive criteria for and against the diagnosis of gastro-oesophageal reflux disease (GERD), and adjunctive metrics that consolidate or refute GERD diagnosis when primary criteria are borderline or inconclusive. An international core and working group was assembled to evaluate research since publication of the original Lyon Consensus, and to vote on statements collaboratively developed to update criteria. The Lyon Consensus 2.0 provides a modern definition of actionable GERD, where evidence from oesophageal testing supports revising, escalating or personalising GERD management for the symptomatic patient. Symptoms that have a high versus low likelihood of relationship to reflux episodes are described. Unproven versus proven GERD define diagnostic strategies and testing options. Patients with no prior GERD evidence (unproven GERD) are studied using prolonged wireless pH monitoring or catheter-based pH or pH-monitoring off antisecretory medication, while patients with conclusive GERD evidence (proven GERD) and persisting symptoms are evaluated using pH-impedance monitoring while on optimised antisecretory therapy. The major changes from the original Lyon Consensus criteria include establishment of Los Angeles grade B oesophagitis as conclusive GERD evidence, description of metrics and thresholds to be used with prolonged wireless pH monitoring, and inclusion of parameters useful in diagnosis of refractory GERD when testing is performed on antisecretory therapy in proven GERD. Criteria that have not performed well in the diagnosis of actionable GERD have been retired. Personalisation of investigation and management to each patient's unique presentation will optimise GERD diagnosis and management.

Optimizing ambulatory reflux monitoring: current findings and future directions

INTRODUCTION

Gastroesophageal reflux disease (GERD) is the most common diagnosis seen in outpatient gastroenterology clinics. The diagnosis is made by a variable combination of symptoms, response to acid suppressive therapy, endoscopic evaluation, and pH testing. In this review, we evaluate how to utilize various reflux testing in clinical practice based on current evidence.

AREAS COVERED

Ambulatory reflux monitoring is a recognized diagnostic tool for clinical decision making in patients with/without established GERD, persistent reflux symptoms, and lack of response to proton pump inhibitor (PPI) therapy. Standard evaluation approaches include 24-hour pH or impedance monitoring via transnasal catheter, prolonged (48 to 96 hour) wireless pH monitoring, and the recently developed mucosal integrity testing. Testing using one of these methods allows for measurement of acid exposure, frequency of reflux, and to phenotype patients to personalize treatment recommendations.

EXPERT OPINION

The primary goal of future studies should be to simplify ambulatory reflux monitoring, reduce diagnostic latency, improve patient tolerance, and to obtain clinical outcomes-based studies. The current paradigm of reflux testing is vastly complex with multiple modalities and shifting cutoffs of pH abnormality that lead to high economic burden on the society.

Improved diagnosis of reflux hypersensitivity

BACKGROUND

Reflux hypersensitivity (RH) is characterized by normal esophageal exposure to acid and positive correlation of symptoms to reflux episodes. Positivity of Symptomatic Index (SI) and/or Symptom Association Probability (SAP) is used diagnostically, though experts support that concordance of both is needed. We evaluated differences among patients with RH and concordance of SI/SAP or not.

METHODS

Patients with typical reflux symptoms without previous GERD diagnosis, submitted simultaneously to Ph-Impedance off PPI and high resolution manometry were included. Self-response to PPI was evaluated. Patients showing SI and/or SAP positivity were considered having RH and further classified to definite RH if both SI/SAP were positive or indefinite if only one positive.

KEY RESULTS

Totally 2659 patients (M/F: 35.6%/64.7%, mean age: 45 ± 14) were included. Final diagnosis was; FH: 21.8%, RH: 29.3% (definite: 14.3%/indefinite: 15%), GERD: 36% and inconclusive GERD: 12.9%. Patients with definite RH showed increased total reflux time, total number of reflux episodes and length of hiatus hernia, and also numerically but not statistically significant increased rates of PPI responsiveness versus indefinite RH and decreased mean nocturnal baseline impedance. Moreover, they showed significantly increased rate of PPI response versus patients with functional heartburn (FH).

CONCLUSION & INFERENCES

Some PPI responsiveness is frequent among patients with RH as also with FH, and cannot discriminate those entities clinically when diagnosing RH using SI and/or SAP positive criterion. Patients with RH and SI/SAP concordance differ from patients without. Implementation of a strict RH definition (both SI and SAP positive) can better distinguish RH from FH and should be used in the future.

Effect of aging and obesity on esophageal mucosal integrity as measured by baseline impedance

AIM

Low mean nocturnal baseline impedance (MNBI) values support gastroesophageal reflux disease (GERD) diagnosis. Recent data denote that age and obesity may affect MNBI. We aimed to evaluate diagnostic MNBI cutoffs as also the effect of aging and body mass index (BMI) on MNBI.

METHODS

In total 311 patients (M/F: 139/172, mean age: 47 ± 13) referred for typical GERD symptoms that have undertaken both high-resolution manometry (HRM) and pH-Impedance studies off PPI were evaluated. MNBI at 3, 5, and 17 cm over lower esophageal sphincter (LES) were evaluated. GERD was diagnosed if acid exposure time (AET) >6%.

RESULTS

Mean BMI was 26.6 ± 5.9 kg/cm2 . GERD was diagnosed in 39.2% and 13.5% had inconclusive GERD. MNBI was correlated to patients' age, BMI, AET, and the length of LES-CD separation and at 3 cm also to the total number of reflux and LES hypotension. In the multivariate analysis MNBI at 3 and 5 cm was independently correlated only to age, BMI, and AET. Patients with definite GERD showed lower MNBI at 3 cm compared with inconclusive GERD though both showed lower values when compared with GERD absence. At 3 cm MNBI ability for diagnosing GERD was good (0.815, p < 0.001 95% CI: 0.766-0.863) with an optimal cutoff point of 1281 Ohm.

CONCLUSION

According to our study findings age and BMI affect independently lower esophageal MNBI values in patients evaluated for GERD. MNBI significantly aids toward GERD diagnosis though in a real-life setting MNBI values much lower than the one previously proposed should be used.

Lemborexant Attenuates Regurgitation without Worsening Objective Parameters on Reflux Monitoring in Patients with Gastroesophageal Reflux Disease and Insomnia: A Single-Arm Proof-of-Concept Study

INTRODUCTION

Esophageal hypersensitivity is associated with gastroesophageal reflux disease (GERD). Since sleep disturbance causes esophageal hypersensitivity, hypnotics may ameliorate GERD. However, zolpidem prolongs esophageal acid clearance. Lemborexant is a new hypnotic with higher efficacy and fewer adverse events than zolpidem. Therefore, the present study investigated the effects of lemborexant on GERD.

METHODS

Patients with heartburn and/or regurgitation and insomnia who did not take acid suppressants or hypnotics in the last month were recruited. Symptom assessments using GerdQ and reflux monitoring were performed before and after a 28-day treatment with 5 mg lemborexant at bedtime. The primary outcome was a change in the total GerdQ score, excluding the score for insomnia. Secondary outcomes were changes in each GerdQ score and the following parameters on reflux monitoring: the acid exposure time (AET), number of reflux events (RE), acid clearance time (ACT), and post-reflux swallow-induced peristaltic wave (PSPW) index.

RESULTS

Sixteen patients (age 45.0 [33.3-56.0], 11 females [68.8%]) completed the intervention (1 patient did not tolerate the second reflux monitoring). The total GerdQ score, excluding the score for insomnia, did not significantly change (8.0 [6.0-9.0] before vs. 7.0 [6.3-9.0] after p = 0.16). GerdQ showed the significant attenuation of regurgitation (2.0 [2.0-3.0] vs. 1.0 [0-2.8] p = 0.0054) but not heartburn (2.5 [1.0-3.0] vs. 1.0 [0.3-2.0] p = 0.175). No significant differences were observed in AET, RE, ACT, or PSPW index before and after the intervention.

CONCLUSION

Lemborexant attenuated regurgitation without the worsening of objective reflux parameters. A randomized placebo-controlled study is warranted in the future.

Application of Artificial Intelligence in Measuring Novel pH-Impedance Metrics for Optimal Diagnosis of GERD

Novel metrics extracted from pH-impedance monitoring can augment the diagnosis of gastroesophageal reflux disease (GERD). Artificial intelligence (AI) is being widely used to improve the diagnostic capabilities of various diseases. In this review, we update the current literature regarding applications of artificial intelligence in measuring novel pH-impedance metrics. AI demonstrates high performance in the measurement of impedance metrics, including numbers of reflux episodes and post-reflux swallow-induced peristaltic wave index and, furthermore, extracts baseline impedance from the entire pH-impedance study. AI is expected to play a reliable role in facilitating measuring novel impedance metrics in patients with GERD in the near future.

Esophageal Mucosal Admittance: A New Technique to Diagnose Gastroesophageal Reflux Disease - Is It Feasible?

Purpose

Esophageal mucosal admittance (MA) is a promising diagnostic method for gastroesophageal reflux disease (GERD). We conducted a study to describe the esophageal MA in patients with reflux symptoms and determine its diagnostic accuracy.

Patients and Methods

We recruited 92 patients with ambulatory pH-impedance monitoring, upper gastrointestinal endoscopy, and MA measured by the tissue conductance meter. MA was measured during endoscopy at 5cm (distal esophagus) and 15cm above the Z line (middle esophagus), repeated at least five times at each position, and median MA was obtained. Afterwards, two biopsies were taken 5cm above the Z line for histopathological evaluation using the Esohisto criteria. Patients were classified as GERD or non-GERD according to the 2018 Lyon consensus.

Results

The mean age was 43.2 years, and 42 patients were males. The most common symptoms were regurgitation (75.0%), belching (65.2%), and heartburn (46.7%). Twenty-three (32.3%) were diagnosed with GERD using the Lyon consensus, and 24 (26.1%) had esophagitis on histopathology. The median MA at the distal and middle esophagus was moderately correlated. The median MA at both positions was higher in the GERD group but only statistically significant in the middle esophagus. MA was not associated with pH-impedance parameters and esophagitis on histopathology. The diagnostic model developed using the logistic regression did not have good accuracy.

Conclusion

MA was not different between GERD and non-GERD patients.

Mean nocturnal baseline impedance and endoscopic mucosal impedance measurements in patients with eosinophilic esophagitis: a new tool for follow up and management?

Eosinophilic esophagitis (EoE) is the second most common cause of chronic esophageal inflammation after GERD, with increasing incidence and prevalence across all age groups. Since current diagnosis and follow up of EoE require endoscopy with biopsies, there is an increased interest in non or less invasive tests for its diagnosis and follow up. Baseline mucosal impedance measurement allows evaluation of mucosal barrier properties and is widely accepted as an adjunct method in GERD diagnosis. As EoE is associated with increased mucosal permeability, the use of baseline impedance to evaluate mucosal integrity has been investigated in several studies. It was found that baseline mucosal impedance, measured either during 24 h reflux monitoring or during endoscopy, was significantly lower in all parts of the esophagus in EoE patients. Impedance measurement correlated with eosinophil counts on biopsies, offering a tool to monitor treatment response. Additionally, baseline impedance patterns differed between those responding to proton pump inhibitor (PPI) treatment and those resistant to PPI, potentially allowing to tailor future treatment to the individual patient. In summary, baseline impedance measurement offers a potential tool for diagnosis and follow up in EoE. Its exact place in EoE treatment is yet to be determined and requires further future studies.

Effect of hiatus hernia on reflux patterns and mucosal integrity in patients with non-erosive reflux disease

BACKGROUND

Hiatus hernia (HH) contributes to development of gastroesophageal reflux disease, Barrett's esophagus and esophageal adenocarcinoma. This study was aimed to investigate the influence of HH on reflux patterns and distal esophageal mucosal integrity in non-erosive reflux disease (NERD).

METHODS

We retrospectively analyzed PPI-refractory NERD patients referred to three tertiary referral centers who underwent high-resolution manometry and off-PPI 24-h impedance-pH monitoring (with or without bile spectrophotometry). Patients with HH ≥2 cm (HH group, n = 42) or no HH (non-HH group, n = 40) with similar esophageal acid exposure time (AET 6%-12%) were included.

KEY RESULTS

Age, gender, BMI, esophageal motility, AET, and esophageal clearance were similar between the two groups. The HH group had higher numbers of total reflux episodes (p = 0.015) with similar proportion of acid/non-acid reflux compared with the non-HH group. Mean nocturnal baseline impedance (MNBI) in the distal esophagus was significantly lower in the HH group than the non-HH group at both 5 cm (p = 0.002) and 3 cm (p = 0.015) above the lower esophageal sphincter. Multivariable regression analysis showed that HH, less non-acid reflux and lower post-reflux swallow-induced peristaltic wave index (PSPWI) were independently associated with lower MNBI. Among 31 patients tested with bile spectrophotometry, the HH group had significantly longer bile exposure time than the non-HH group (p = 0.011), and bile reflux inversely and significantly correlated with MNBI (rho = -0.75, p &lt; 0.001).

CONCLUSIONS AND INFERENCES

Hiatus hernia, less non-acid reflux and lower PSPWI were associated with lower MNBI. HH impairs distal esophageal mucosal integrity, the mechanism of which we speculate to be through excessive bile reflux.

Mean nocturnal baseline impedance, a novel metric of multichannel intraluminal impedance-pH monitoring in diagnosing gastroesophageal reflux disease

Gastroesophageal reflux disease (GERD) is a common disease with increasing prevalence worldwide. However, the diagnosis of GERD is challenging because there are no definite gold standard criteria. Recently, a novel impedance parameter, namely mean nocturnal baseline impedance (MNBI), has been proposed, which reflects the burden of longitudinal reflux and the integrity of esophageal mucosa. MNBI has shown an immense promise for increasing the diagnostic rate of multichannel intraluminal impedance-pH (MII-pH) monitoring and predicting the response to proton pump inhibitor (PPI) or anti-reflux intervention in patients with reflux symptoms. The present paper reviews the association between baseline impedance and esophageal mucosal integrity, the acquisition of MNBI in 24-h MII-pH monitoring, the clinical utilization of MNBI in improving the diagnosis rate of GERD in patients with typical reflux symptoms, predicting the response to PPI or anti-reflux treatment in these patients, the utilization of MNBI in diagnosing patients with atypical symptoms or extra-esophageal symptoms, and the correlation between reflux burden and MNBI. MNBI should be routinely assessed using MII-pH monitoring.

Editorial: Lyon consensus metrics-towards personalised diagnosis of non-erosive reflux disease

This article is linked to Frazzoni et al papers. To view these articles, visit https://doi.org/10.1111/apt.16838 and https://doi.org/10.1111/apt.16911

Low Mean Nocturnal Baseline Impedance is Associated With a Pathological Acid Exposure Time in Children

BACKGROUND

The baseline impedance (BI) and the mean nocturnal baseline impedance (MNBI) serve as markers of mucosal integrity in patients with pathologic acid exposure time (AET). This work aims to investigate the association between the BI and MNBI with the AET in children.

METHODOLOGY

A retrospective study was performed in children ≤18 years old with suspicion of gastroesophageal reflux disease who underwent both endoscopy and pH-impedance monitoring (pH-MII). Esophagitis was graded according to the Los Angeles classification. The pathological AET was determined depending on the age (≥5% in patients >1 year and ≥10% in those ages ≤1 year). For the BI, 60 s measurements were taken every 4 h, and for the MNBI, 3 10 min measurements were taken between 1.00 and 3:00 am; then, they were averaged. The means of BI and MNBI were compared with each other, with the AET, and other variables.

RESULTS

Sixty-eight patients were included, 25% of patients presented pathological AET. The mean of the MNBI was higher than BI in channels 6 (2195 vs 1997 Ω, P = 0.011) and 5 (2393 vs 2228 Ω, P = 0.013). BI and MNBI at channel 6 were lower in patients with pathological AET than in those with normal AET (1573 vs 2138 Ω, P = 0.007) and (1592 vs 2396 Ω, P = 0.004), respectively.

CONCLUSIONS

Children with pathological AET had lower impedance values than those with normal AET. BI and MNBI measurements should be part of the routine MII-pH assessment in children.

Episode-level reflux characteristics: How experienced reviewers differentiate true reflux from artifact on pH-impedance studies

BACKGROUND

Accurate reflux episode identification is crucial for pH-impedance interpretation. Individual reflux episode characteristics associated with inter-reviewer concordance are incompletely understood.

METHODS

Ambulatory pH-impedance studies from 19 GERD patients (median age 52 years, 78.9% F) were analyzed by 5 reviewers. Metadata from pH-impedance studies were exported to a dedicated software tool designed to compare episode-by-episode identification between reviewers within a ±7.5 s window. Patient position, acidic vs. nonacidic episodes, acid clearance time (ACT), bolus clearance time (BCT), and proximal extent of reflux episodes were compared between episodes identified by all reviewers against those identified by automated analysis, and one to four reviewers, respectively.

RESULTS

Automated analysis identified 1644 episodes (median 78 episodes per patient, IQR 64-108), of which 84.9% were identified by ≥3 reviewers and 57.1% by all reviewers; 339 unique episodes were added by at least 1 reviewer. Characteristics defining 5 reviewer concordance included acid reflux episodes (88.9%), upright episodes (88.4%), high proximal extent (median 17 cm, IQR 15-17 cm), and longer acid clearance times (67.0 s, IQR 29.0-146.0 s) (P < 0.001 compared to 1-4 reviewer concordance for each). In contrast, 1 reviewer-identified episodes were 69.8% acidic, 76.9% upright, and limited to the distal esophagus. Using 5-reviewer concordance, designation of GERD evidence changed from automated analysis in 16%-19% of patients.

CONCLUSIONS

Acidic episodes with high proximal extent in the upright position and longer acid clearance times on pH-impedance studies have the highest concordance for identification by expert reviewers. Reflux episode identification may be influenced by reviewer opinion despite availability of established criteria.

Clinical use of mean nocturnal baseline impedance and post-reflux swallow-induced peristaltic wave index for the diagnosis of gastro-esophageal reflux disease

The clinical diagnosis of gastro-esophageal reflux disease (GERD) is based on the presence of typical esophageal troublesome symptoms. In clinical practice, heartburn relief following a proton pump inhibitor (PPI) trial or endoscopy can confirm a diagnosis of GERD. In cases of diagnostic uncertainty or before anti-reflux interventions, combined impedance-pH monitoring (MII-pH) provides a comprehensive assessment of both physical and chemical properties of the refluxate, allowing to achieve a conclusive diagnosis of GERD. Recently, the Lyon Consensus proposed the use of mean nocturnal baseline impedance (MNBI) and post-reflux swallow-induced peristaltic wave index (PSPW-I) as novel MII-pH metrics to support the diagnosis of GERD. The calculation of MNBI and PSPW-I currently needs to be performed manually, but artificial intelligence systems for the automated analysis of MII-pH tracings are being developed. Several studies demonstrated the increased diagnostic yield MNBI and PSPW-I for the categorization of patients with GERD at both on- and off-PPI MII-pH monitoring. Accordingly, we performed a narrative review on the clinical use and diagnostic yield of MNBI and PSPW-I when the diagnosis of GERD is uncertain. Based on currently available evidence, we strongly support the evaluation of PSPW-I and MNBI as part of the standard assessment of MII-pH tracings for the evaluation of GERD, especially in patients with endoscopy-negative heartburn.

Value of pH Impedance Monitoring While on Twice-Daily Proton Pump Inhibitor Therapy to Identify Need for Escalation of Reflux Management

BACKGROUND AND AIMS

Acid exposure time (AET) and reflux episode thresholds from the Lyon Consensus may not apply for pH impedance studies performed while on proton pump inhibitor (PPI) therapy. We aimed to determine metrics from "on PPI" pH impedance studies predicting need for escalation of therapy.

METHODS

De-identified pH impedance studies performed while on twice-daily PPI (Diversatek, Boulder, CO) in healthy volunteers (n = 66, median age 37.5 years, 43.9% female), and patients with proven gastroesophageal reflux disease (GERD) (European heartburn-predominant cohort: n = 43, median age 57.0 years, 55.8% female; North American regurgitation-predominant cohort: n = 42, median age 41.6 years, 42.9% female) were analyzed. Median values and interquartile ranges for pH impedance metrics in healthy volunteers were compared with proven GERD patients with and without 50% symptom improvement on validated measures. Receiver operating characteristic (ROC) analyses identified optimal thresholds predicting symptom response.

RESULTS

Both conventional and novel reflux metrics were similar between PPI responders and nonresponders (P ≥ .1 for each) despite differences from healthy volunteers. Combinations of metrics associated with conclusively abnormal reflux burden (AET >4%, >80 reflux episodes) were seen in 32.6% and 40.5% of heartburn and regurgitation-predominant patients, respectively, 57.1% and 82.4% of whom reported nonresponse; and 85% with these metrics improved with invasive GERD management. On ROC analysis, AET threshold of 0.5% modestly predicted nonresponse (sensitivity, 0.62; specificity, 0.51; P = .22), and 40 reflux episodes had better performance characteristics (sensitivity, 0.80; specificity, 0.51; P = .002); 79% with these metrics improved with invasive GERD management.

CONCLUSION

Combinations of abnormal "on PPI" pH impedance metrics are associated with PPI nonresponse in proven GERD patients, and can be targeted for treatment escalation, including surgery, particularly in regurgitation-predominant GERD.

Conventional and simple methods of measuring esophageal nocturnal baseline impedance show excellent agreement

OBJECTIVES

Mean nocturnal baseline impedance (MNBI) shows promise in investigating reflux disease by reflecting esophageal mucosal integrity. This study aimed to measure MNBI by both conventional and simple methods in patients with laryngopharyngeal reflux (LPR) and gastroesophageal reflux disease (GERD) in order to evaluate the efficacy of the simple measurement method.

METHODS

Altogether 187 patients were divided into LPR (n = 105) or GERD (n = 82) groups according to their predominant symptom profile, and underwent off-therapy impedance-pH monitoring. MNBI was measured by both the conventional and simple methods. The Bland-Altman plots were constructed to assess mean differences and to identify bias in the two measurement methods.

RESULTS

For the two measurement methods, mean difference was (-89 ± 328) Ω in the distal esophagus, (-6 ± 653) Ω in the proximal esophagus, and (128 ± 577) Ω in the pharynx, respectively. There was a strong correlation between conventional and simple MNBI values, with  the coefficient of 0.940 in the distal esophagus, 0.463 in the proximal esophagus, and 0.712 in the pharynx (all P < 0.001).

CONCLUSIONS

There was an excellent agreement between the conventional and simple methods of MNBI measurement, with no evidence of proportional bias. Conventional and simple MNBI values correlated excellently in the distal esophagus and moderately well in the proximal esophagus and pharynx. This study supports the use of the simple method of measuring MNBI to enhance diagnoses of reflux disease.

Advances in the diagnosis of GERD

Gastroesophageal reflux disease (GERD) is considered one of the most frequent chronic gastrointestinal diseases globally with high costs due to treatment and investigations.First line therapy is with proton pump inhibitors, those who do not respond to initial treatment usually require further investigations such as upper gastrointestinal endoscopy or ambulatory 24-hours esophageal pH monitoring. The total time of exposure to acid and the DeMeester score represent the most useful parameters associated with conventional pH-metry, because they can identify gastroesophageal reflux disease.Although pH-metry is considered the gold standard for the evaluation of gastroesophageal reflux disease, new impedance-based parameters have been introduced in recent years with the role of increasing the accuracy of diagnosing gastroesophageal reflux disease and characterizing the type of reflux. The development of multichannel intraluminal pH-impedance has improved the ability to detect and quantify gastroesophageal reflux. New parameters such as post-reflux swallowing peristaltic wave (PSPW) index and the mean nocturnal basal impedance (MNBI) have recently been introduced to assess GERD phenotypes more accurately. This review evaluates current GERD diagnotic tools while also taking a brief look at newer diagnostic parameters like PSPW and MNBI.

Artificial intelligence automates and augments baseline impedance measurements from pH-impedance studies in gastroesophageal reflux disease

BACKGROUND

Artificial intelligence (AI) has potential to streamline interpretation of pH-impedance studies. In this exploratory observational cohort study, we determined feasibility of automated AI extraction of baseline impedance (AIBI) and evaluated clinical value of novel AI metrics.

METHODS

pH-impedance data from a convenience sample of symptomatic patients studied off (n = 117, 53.1 ± 1.2 years, 66% F) and on (n = 93, 53.8 ± 1.3 years, 74% F) anti-secretory therapy and from asymptomatic volunteers (n = 115, 29.3 ± 0.8 years, 47% F) were uploaded into dedicated prototypical AI software designed to automatically extract AIBI. Acid exposure time (AET) and manually extracted mean nocturnal baseline impedance (MNBI) were compared to corresponding total, upright, and recumbent AIBI and upright:recumbent AIBI ratio. AI metrics were compared to AET and MNBI in predicting  ≥ 50% symptom improvement in GERD patients.

RESULTS

Recumbent, but not upright AIBI, correlated with MNBI. Upright:recumbent AIBI ratio was higher when AET  > 6% (median 1.18, IQR 1.0-1.5), compared to  < 4% (0.95, IQR 0.84-1.1), 4-6% (0.89, IQR 0.72-0.98), and controls (0.93, IQR 0.80-1.09, p ≤ 0.04). While MNBI, total AIBI, and the AIBI ratio off PPI were significantly different between those with and without symptom improvement (p < 0.05 for each comparison), only AIBI ratio segregated management responders from other cohorts. On ROC analysis, off therapy AIBI ratio outperformed AET in predicting GERD symptom improvement when AET was  > 6% (AUC 0.766 vs. 0.606) and 4-6% (AUC 0.563 vs. 0.516) and outperformed MNBI overall (AUC 0.661 vs. 0.313).

CONCLUSIONS

BI calculation can be automated using AI. Novel AI metrics show potential in predicting GERD treatment outcome.

The esophageal mucosal barrier in health and disease: mucosal pathophysiology and protective mechanisms

Diseases of the esophagus, such as gastroesophageal reflux (GER), can result in changes to mucosal integrity, neurological function, and the microbiome. Although poorly understood, both age and GER can lead to changes to the enteric nervous system. In addition, the esophagus has a distinct microbiome that can be altered in GER. Mucosal integrity is also at risk due to persistent damage from acid. Diagnostic tools, such as ambulatory pH/impedance testing and esophageal mucosal impedance, can assess short-term and longitudinal GER burden, which can also assess the risk for mucosal compromise. The quality of the mucosal barrier is determined by its intercellular spaces, tight junctions, and tight junction proteins, which are represented by claudins, occludins, and adhesion molecules. Fortunately, there are protective factors for mucosal integrity that are secreted by the esophageal submucosal mucous glands and within saliva that are augmented by mastication. These protective factors have potential as therapeutic targets for GER. In this article, we aim to review diagnostic tools used to predict mucosal integrity, aging, and microbiome changes to the esophagus and esophageal mucosal defense mechanisms.

Normal values and regional differences in oesophageal impedance-pH metrics: a consensus analysis of impedance-pH studies from around the world

OBJECTIVE

Limitations of existing impedance-pH thresholds include small sample size of normative studies, inclusion of artefactual pH drops and incorrect identification of impedance reflux events. We aimed to obtain new impedance-pH thresholds from expert consensus analysis of tracings from a large number of healthy subjects.

DESIGN

Of 541 studies performed worldwide using two different systems (Diversatek, USA, and Laborie, Netherlands), 150 tracings with oesophageal diagnoses, behavioural disorders and study-related artefacts were excluded. The remainder studies were subject to two reviewer consensus analysis, in-person or through video conference, consisting of editing meals and pH drops, identification of impedance reflux and postreflux swallow-induced peristaltic wave (PSPW) using strict pre-established criteria and measurement of distal mean nocturnal baseline impedance (MNBI).

RESULTS

Consensus analysis was performed in 391 tracings (age 32.7 years, range 18-71, 54.2% female). Normative thresholds were significantly different between Diversatek and Laborie (total acid exposure time: 2.8% and 5%; reflux episodes: 55 and 78; MNBI at 3 cm: 1400 and 1500 ohms, at 5 cm: 1400 and 1800 ohms). Males had higher acid exposure, more reflux episodes and lower MNBI. Significant regional differences were identified, including higher PSPW scores in Western countries, and higher MNBI in Asia using Diversatek, and higher acid exposure in the Netherlands, higher MNBI in Asia and South Africa, and lower MNBI in Turkey using Laborie.

CONCLUSION

Normal impedance-pH monitoring thresholds have regional and system-related differences. Clinical interpretation needs to use normal thresholds valid for the system used and world region, following careful editing of the tracings.