Impedance nadir values correlate with barium bolus amount

New parameter for quantifying bolus transit with high-resolution impedance manometry: A comparison with simultaneous esophagogram

BACKGROUND

Esophageal bolus transit can be assessed using esophagogram or high-resolution impedance manometry (HRIM). The three-dimensional volume of inverted impedance (VII) has been developed to quantify the residual bolus between each swallow through spatiotemporal analysis. However, this novel metric has not been validated against simultaneous esophagogram.

METHODS

A total of nine healthy volunteers (Seven males, aged 19-45 years) were prospectively evaluated with HRIM and barium esophagogram. In addition, 21 symptomatic patients (12 males, aged 20-85 years) without major motility disorder were also included. The VII was estimated from HRIM data using MATLAB program and was compared with residual bolus volume in the esophagus estimated from simultaneous esophagogram.

KEY RESULTS

A total of 80 swallows (24 in controls and 56 in patients) were analyzed. Results from the VII method were concordant with the bolus transit pattern estimated from the esophagogram in 91.3% (73/80) of swallows. The correlation between quantitative data from VII and the volume of residual bolus estimated from esophagogram was strong in both groups with a Pearson's correlation coefficient of 0.805 for healthy volunteers and 0.730 for symptomatic patients. The intraclass correlation coefficient of VII between the three swallows within a subject was 0.901 in healthy subjects and 0.705 in patients, indicating a modest reliability of this method.

CONCLUSIONS AND INFERENCES

The newly developed VII method is a reliable method in assessing residual bolus volume in the esophagus based on comparison with bolus volume estimated from simultaneous esophagogram.

Measuring Vallecular Volume on Flexible Endoscopic Evaluation of Swallowing: A Proof of Concept Study

Currently, no method exists to measure the size of pharyngeal and laryngeal structures on endoscopy. Imaging for dysphagia diagnostic techniques, for the most part, still relies on qualitative assumptions and cursory visual examinations to induce patients' swallowing safety and function. In this proof of concept study, we measured vallecular cavity volume using simultaneous modified barium swallows (MBS) and flexible endoscopic evaluation of swallowing (FEES). Similar to the three-dimensional image compilation fields of facial reconstruction, medical imagery, and forensic science, this proposed methodology combines the two-dimensional images yielded in FEES and MBS videos to calculate estimates of the valleculae in a 3D perspective. A tracking tool was used to measure distances on MBS, while endoscopic specifications were used to find distances on FEES. This combination of ratio measurements allowed for measurement on both the MBS and FEES. In a sample of n = 37 dysphagia patients referred for MBS/FEES studies, the mean distance from the tip of endoscope to the closest point of epiglottis was 25.38 mm, the mean vallecular area outlined on MBS video was 84.72 mm², the mean epiglottal width was 18.16 mm, and the mean vallecular volume was 1.55 mL. Future application could include tracking growth of tumors, glottic opening, volume of residue and tracking of any other important outcome involving movement, size, and targets of interest with higher precision.

Esophageal Impedance Monitoring: Clinical Pearls and Pitfalls

The development of intraluminal esophageal impedance monitoring has improved our ability to detect and measure gastroesophageal reflux without dependence on acid content. This ability to detect previously unrecognized weak or nonacid reflux episodes has had important clinical implications in the diagnosis and management of gastroesophageal reflux disease (GERD). In addition, with the ability to assess bolus transit within the esophageal lumen, impedance monitoring has enhanced the recognition and characterization of esophageal motility disorders in patients with nonobstructive dysphagia. The assessment of the intraluminal movement of gas and liquid has also been proven to be of diagnostic value in conditions such as rumination syndrome and excessive belching. Further, alternative applications of impedance monitoring, such as the measurement of mucosal impedance, have provided novel insights into assessing esophageal mucosal integrity changes as a consequence of inflammatory change. Future applications for esophageal impedance monitoring also hold promise in esophageal conditions other than GERD. However, despite all of the clinical benefits afforded by esophageal impedance monitoring, important clinical and technical shortcomings limit its diagnostic value and must be considered when interpreting study results. Overinterpretation of studies or application of impedance monitoring in patients can have deleterious clinical implications. This review will highlight the clinical benefits and limitations of esophageal impedance monitoring and provide clinical pearls and pitfalls associated with this technology.

Remifentanil alters sensory neuromodulation of swallowing in healthy volunteers: quantification by a novel pressure-impedance analysis

Exposure to remifentanil contributes to an increased risk of pulmonary aspiration, likely through reduced pharyngeal contractile vigor and diminished bolus propulsion during swallowing. We employed a novel high-resolution pressure-flow analysis to quantify the biomechanical changes across the upper esophageal sphincter (UES). Eleven healthy young (23.3 ± 3.1 yr old) participants (7 men and 4 women) received remifentanil via intravenous target-controlled infusion with an effect-site concentration of 3 ng/ml. Before and 30 min following commencement of remifentanil administration, participants performed ten 10-ml saline swallows while pharyngoesophageal manometry and electrical impedance data were recorded using a 4.2-mm-diameter catheter housing 36 circumferential pressure sensors. Remifentanil significantly shortened the duration of UES opening (P < 0.001) and increased residual UES pressure (P = 0.003). At the level of the hypopharynx, remifentanil significantly shortened the latency from maximum bolus distension to peak contraction (P = 0.004) and significantly increased intrabolus distension pressure (P = 0.024). Novel mechanical states analysis revealed that the latencies between the different phases of the stereotypical UES relaxation sequence were shortened by remifentanil. Reduced duration of bolus flow during shortened UES opening, in concert with increased hypopharyngeal distension pressures, is mechanically consistent with increased flow resistance due to a more rapid bolus flow rate. These biomechanical changes are congruent with modification of the physiological neuroregulatory mechanism governing accommodation to bolus volume.

The Reliability of Pharyngeal High Resolution Manometry with Impedance for Derivation of Measures of Swallowing Function in Healthy Volunteers

Purpose. We evaluated the intra- and interrater agreement and test-retest reliability of analyst derivation of swallow function variables based on repeated high resolution manometry with impedance measurements. Methods. Five subjects swallowed 10 × 10 mL saline on two occasions one week apart producing a database of 100 swallows. Swallows were repeat-analysed by six observers using software. Swallow variables were indicative of contractility, intrabolus pressure, and flow timing. Results. The average intraclass correlation coefficients (ICC) for intra- and interrater comparisons of all variable means showed substantial to excellent agreement (intrarater ICC 0.85–1.00; mean interrater ICC 0.77–1.00). Test-retest results were less reliable. ICC for test-retest comparisons ranged from slight to excellent depending on the class of variable. Contractility variables differed most in terms of test-retest reliability. Amongst contractility variables, UES basal pressure showed excellent test-retest agreement (mean ICC 0.94), measures of UES postrelaxation contractile pressure showed moderate to substantial test-retest agreement (mean Interrater ICC 0.47–0.67), and test-retest agreement of pharyngeal contractile pressure ranged from slight to substantial (mean Interrater ICC 0.15–0.61). Conclusions. Test-retest reliability of HRIM measures depends on the class of variable. Measures of bolus distension pressure and flow timing appear to be more test-retest reliable than measures of contractility.

Oesophageal dysphagia: manifestations and diagnosis

Oesophageal dysphagia is a common symptom, which might be related to severe oesophageal diseases such as carcinomas. Therefore, an organic process must be ruled out in the first instance by endoscopy in all patients presenting with dysphagia symptoms. The most prevalent obstructive aetiologies are oesophageal cancer, peptic strictures and eosinophilic oesophagitis. Eosinophilic oesophagitis is one of the most common causes of dysphagia in adults and children, thus justifying the need to obtain oesophageal biopsy samples from all patients presenting with unexplained dysphagia. With the advent of standardized high-resolution manometry and specific metrics to characterize oesophageal motility, the Chicago classification has become a gold-standard algorithm for manometric diagnosis of oesophageal motor disorders. In addition, sophisticated investigations and analysis methods that combine pressure and impedance measurement are currently in development. In the future, these techniques might be able to detect subtle pressure abnormalities during bolus transport, which could further explain pathophysiology and symptoms. The degree to which novel approaches will help distinguish dysphagia caused by motor abnormalities from functional dysphagia still needs to be determined.

Correlation of esophageal clearance and dysphagia symptom assessment after treatment for achalasia

BACKGROUND

Early relapse after treatment of achalasia occurs in 10-32 % of patients. The best method to follow up these patients is not known. Symptoms often do not correlate with esophageal clearance: some patients are oligosymptomatic despite persistent esophageal stasis/dilatation.

AIM

The aim was to compare two methods of measurement of esophageal clearance (impedance manometry with barium swallow) in achalasia patients following treatment. Symptom assessment (Eckardt score/detailed dysphagia questions) was correlated with objective measurements of esophageal stasis (barium swallow and impedance manometry) in achalasia patients following treatment.

METHODS

Post-treatment patients were followed up after median 38.4 months (median range 1-144 months). Symptoms were quantified using the Eckardt score and detailed dysphagia questions. Timed barium swallow quantified distal esophageal retention 0.5, 1, 3, and 5 minutes after oral contrast and impedance manometry assessed total and segmental esophageal clearance during water/viscous swallows and free drinking (200 mL).

RESULTS

Thirty-two patients (7 women, age 48.3; range 20-74) completed all investigations. Bolus retention in the distal esophagus assessed by impedance correlated well with barium swallow. There were no differences in impedance and timed barium swallow parameters between patients with Eckardt score 0-2 points or ≥3 points. Nine (28%) patients had an Eckardt score ≥3 points and 21 (66%) had ≥1 point in the detailed dysphagia questions. Patients without any dysphagia history had lower barium column height and width at 3 and 5 minutes compared to those with ≥1 positive answer in the detailed dysphagia questions. Correlation between the Eckardt score and detailed dysphagia questions was moderately good (r = 0.546; p = 0.001).

CONCLUSION

A detailed history of esophageal dysphagia rather than the Eckardt score is more sensitive to detect oligosymptomatic patients with disturbed esophageal clearance. Impedance manometry correlates well with the timed-barium swallow examination and represents an alternative objective assessment as it avoids radiation exposure.

Impedance as an adjunct to manometric testing to investigate symptoms of dysphagia: What it has failed to do and what it may tell us in the future

Dysphagia is a common reason for referral for investigations of oesophageal motility. Impedance measurement has now been incorporated into commercially available diagnostic manometry systems for more than a decade. This innovation, which offered the ability to record patterns of bolus transport without the need for simultaneous radiology, has for the most part failed to live up to expectations, offering few additional diagnostic insights. This review examines the potential pitfalls related to how impedance patterns are currently analysed and introduces and discusses the new concept of pressure-flow analysis integrating pressure and impedance measurements to derive new metrics linked to the pressures occurring within and around the bolus as it is being transported.

The effect of bilateral superior laryngeal nerve lesion on swallowing: a novel method to quantitate aspirated volume and pharyngeal threshold in videofluoroscopy

The purpose was to determine the effect of bilateral superior laryngeal nerve (SLN) lesion on swallowing threshold volume and the occurrence of aspiration, using a novel measurement technique for videofluoroscopic swallowing studies (VFSS) in infant pigs. We used a novel radiographic phantom to assess volume of the milk containing barium from fluoroscopy. The custom made phantom was firstly calibrated by comparing image intensity of the phantom with known cylinder depths. Secondly, known volume pouches of milk in a pig cadaver were compared to volumes calculated with the phantom. Using these standards, we calculated the volume of milk in the valleculae, esophagus and larynx, for 205 feeding sequences from four infant pigs feeding before and after had bilateral SLN lesions. Swallow safety was assessed using the tested and validated IMPAS (Dysphagia 28(2):178-187, 2013). The log-linear correlation between image intensity values from the phantom filled with barium milk and the known phantom cylinder depths was strong (R (2) > 0.95), as was the calculated volumes of the barium milk pouches. The threshold volume of bolus in the valleculae during feeding was significantly larger after bilateral SLN lesion than in control swallows (p < 0.001). The IMPAS score increased in the lesioned swallows relative to the controls, indicating substantially impaired swallowing (p < 0.001). Bilateral SLN lesion dramatically increased the aspiration incidence and the threshold volume of bolus in valleculae. The use of this phantom permits quantification of the aspirated volume of fluid, allowing for more accurate 3D volume estimation from 2D X-ray in VFSS.

The four phases of esophageal bolus transit defined by high-resolution impedance manometry and fluoroscopy

We aimed to model esophageal bolus transit based on esophageal pressure topography (EPT) landmarks, concurrent intrabolus pressure (IBP), and esophageal diameter as defined with fluoroscopy. Ten healthy subjects were studied with high-resolution impedance manometry and videofluoroscopy. Data from four 5-ml barium swallows (2 upright, 2 supine) in each subject were analyzed. EPT landmarks were utilized to divide bolus transit into four phases: phase I, upper esophageal sphincter (UES) opening; phase II, UES closure to the transition zone (TZ); phase III, TZ to contractile deceleration point (CDP); and phase IV, CDP to completion of bolus emptying. IBP and esophageal diameter were analyzed to define functional differences among phases. IBP exhibited distinct changes during the four phases of bolus transit. Phase I was associated with filling via passive dilatation of the esophagus and IBP reflective of intrathoracic pressure. Phase II was associated with auxotonic relaxation and compartmentalization of the bolus distal to the TZ. During phase III, IBP exhibited a slow increase with loss of volume related to peristalsis (auxotonic contraction) and passive dilatation in the distal esophagus. Phase IV was associated with the highest IBP and exhibited isometric contraction during periods of nonemptying and auxotonic contraction during emptying. IBP may be used as a marker of esophageal wall state during the four phases of esophageal bolus transit. Thus abnormalities in IBP may identify subtypes of esophageal disease attributable to abnormal distensibility or neuromuscular dysfunction.

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

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.

Parameters for quantifying bolus retention with high-resolution impedance manometry

BACKGROUND

This study aimed to develop a methodology for quantifying esophageal bolus retention using a high-resolution esophageal impedance topography (EIT) technique.

METHODS

The ability of impedance to quantify bolus retention was validated by comparison with concurrent fluoroscopic imaging (barium bolus) in 10 healthy subjects. High-resolution impedance manometry (HRIM) studies without fluoroscopy were performed in another 15 healthy subjects to define normal values using saline. HRIM data from each subject were analyzed using a MATLAB program customized for calculating the esophageal impedance integral (EII) prior to the contraction wave front as EII1 and after the contraction as EII2, and presented as a ratio of EII2/EII1, which was compared to the percent of barium areas retained in the esophagus on fluoroscopy determined by a blinded reviewer.

KEY RESULTS

In 93% (37/40) of barium swallows, the results from the EIT method were in agreement with fluoroscopy results with one of three patterns: (1) 25 normal bolus transit, (2) eight bolus stasis, and (3) four retrograde escape or reflux. Three swallows (8%) had slight retention identified by EIT, but no retention detected by fluoroscopy. The correlation between percent of bolus retained in the esophagus detected by fluoroscopy and percent of bolus retention (EII2/EII1) after swallows with EIT method was r = 0.96 (p < 0.001) in supine and r = 0.69 (p < 0.001) in upright position.

CONCLUSIONS & INFERENCES

The EII ratio (EII2/EII1) is a surrogate for the fraction of retained bolus after a swallow and this metric may be useful in better defining esophageal function.

Inter- and intra-rater reproducibility of automated and integrated pressure-flow analysis of esophageal pressure-impedance recordings

BACKGROUND

Automated impedance manometry pressure-flow analysis (AIM analysis) determines pressure measurements relative to bolus flow and has to date shown subtle variations in esophageal motility in relation to dysphagia. In this study, we assessed intra- and inter-rater reproducibility of AIM metrics derived using purpose designed software.

METHODS

Fifty patients referred for evaluation of gastro-esophageal reflux symptoms (33 men, age 52 ± 1.9 years) underwent combined high-resolution impedance manometry and completed a dysphagia questionnaire. From 10 liquid and 10 viscous swallows, a subset of four swallows (two saline and two viscous) was systematically selected from each patient for manual and AIMplot analysis, which was performed twice by five observers (two experts, three non-experts). Intra- and inter-rater agreement were determined using intraclass correlation coefficients.

KEY RESULTS

AIMplot-based analysis showed high intra-rater and inter-rater reproducibility for all metrics (mean ICCs of 0.95 and 0.94, respectively). Reproducibility of metrics derived for liquid and viscous did not differ (ICCs of 0.96 and 0.91 for liquid and viscous, respectively). In addition, metrics derived by experts had an equivalent level of reproducibility compared to non-experts (ICCs of 0.96 and 0.94, respectively). Variables that could be derived with commercial software (ManoView™) correlated highly with variables from AIMplot-based analysis, such as 4-s integrated relaxation pressure (r = 0.85) and the 20-mmHg isobaric contour defect (r = 0.92).

CONCLUSIONS & INFERENCES

Esophageal AIM analysis is highly reproducible, independent of an observer's level of experience in esophageal motility. Therefore, AIM analysis produces data that are reliable for clinical and research purposes.