Relationship between distension-contraction waveforms during esophageal peristalsis: effect of bolus volume, viscosity, and posture

Why so Many Patients With Dysphagia Have Normal Esophageal Function Testing

Esophageal peristalsis involves a sequential process of initial inhibition (relaxation) and excitation (contraction), both occurring from the cranial to caudal direction. The bolus induces luminal distension during initial inhibition (receptive relaxation) that facilitates smooth propulsion by contraction travelling behind the bolus. Luminal distension during peristalsis in normal subjects exhibits unique characteristics that are influenced by bolus volume, bolus viscosity, and posture, suggesting a potential interaction between distension and contraction. Examining distension-contraction plots in dysphagia patients with normal bolus clearance, ie, high-amplitude esophageal peristaltic contractions, esophagogastric junction outflow obstruction, and functional dysphagia, reveal 2 important findings. Firstly, patients with type 3 achalasia and nonobstructive dysphagia show luminal occlusion distal to the bolus during peristalsis. Secondly, patients with high-amplitude esophageal peristaltic contractions, esophagogastric junction outflow obstruction, and functional dysphagia exhibit a narrow esophageal lumen through which the bolus travels during peristalsis. These findings indicate a relative dynamic obstruction to bolus flow and reduced distensibility of the esophageal wall in patients with several primary esophageal motility disorders. We speculate that the dysphagia sensation experienced by many patients may result from a normal or supernormal contraction wave pushing the bolus against resistance. Integrating representations of distension and contraction, along with objective assessments of flow timing and distensibility, complements the current classification of esophageal motility disorders that are based on the contraction characteristics only. A deeper understanding of the distensibility of the bolus-containing esophageal segment during peristalsis holds promise for the development of innovative medical and surgical therapies to effectively address dysphagia in a substantial number of patients.

Esophageal wall compliance/stiffness during peristalsis in patients with functional dysphagia and high-amplitude esophageal contractions

Recent studies that utilized distension/contraction plots to study peristalsis reveal poor distension of the esophagus in patients with functional dysphagia and high-amplitude contractions [high-amplitude esophageal contractions (HAECs)] even though the contraction phase of peristalsis is normal in these patients. Our goal was to determine biomechanical properties of the esophageal wall and bolus flow characteristics in patients with functional dysphagia and HAEC during primary peristalsis. Studies were performed on 30 healthy subjects, 30 patients with functional dysphagia, and 25 patients with HAEC. Subjects swallowed 10 mL, 0.5 N saline bolus in the Trendelenburg position to study primary peristalsis. A custom-built software (Dplots) determined peak distension from the impedance measurements, pressure at peak distension, wall tension (pressure × radius), wall distensibility [cross-sectional area (CSA)/pressure], and bolus flow (cm3/s) in four segments of esophagus (between upper and lower esophageal sphincter). Luminal CSA of distal esophagus was smaller, and average bolus flow rate was faster in patients with functional dysphagia and HAEC. Esophageal wall distensibility, a measure of esophageal wall compliance was lower and wall tension was higher in the distal esophagus of both patient groups compared with normal subjects. Ultrasound imaging confirmed poor distension of the esophagus. A trend toward greater wall thickness at the peak of distension was found in patients with functional dysphagia compared with normal subjects. A stiffer or noncompliant esophageal wall is the reason for poor distension of the esophagus during primary peristalsis in patients with functional dysphagia and HAEC.NEW & NOTEWORTHY We studied healthy asymptomatic subject, patients with functional dysphagia (FD), and patients with high-amplitude esophageal contractions (HAEC). Our data show that in patients with HAEC and functional dysphagia, luminal distension is smaller (low luminal CSA at peak distension), intraluminal pressure is higher, and liquid bolus travels faster through the esophagus as compared with normal subjects. We conclude that patients with functional dysphagia and HAEC have a stiffer distal esophageal wall during bolus transport related to primary peristalsis.

Distension contraction plots of pharyngeal/esophageal peristalsis: next frontier in the assessment of esophageal motor function

Esophageal peristalsis consists of initial inhibition (relaxation) followed by excitation (contraction), both of which move sequentially in the aboral direction. Initial inhibition results in receptive relaxation and bolus-induced luminal distension, which allows propulsion by the contraction with minimal resistance to flow. Similar to the contraction wave, luminal distension has unique waveform characteristics in normal subjects; both are modulated by bolus volume, bolus viscosity, and posture, suggesting a possible cause-and-effect relationship between the two. Distension contraction plots in patients with dysphagia with normal bolus clearance [high-amplitude esophageal contractions (HAECs), esophagogastric junction outflow obstruction (EGJOO), and functional dysphagia (FD)] reveal two major findings: 1) unlike normal subjects, there is luminal occlusion distal to bolus during peristalsis in certain patients, i.e., with type 3 achalasia and nonobstructive dysphagia; and 2) bolus travels through a narrow lumen esophagus during peristalsis in patients with HAECs, EGJOO, and FD. Aforementioned findings indicate a relative dynamic obstruction to the bolus flow during peristalsis and reduced distensibility of esophageal wall in the bolus segment of the esophagus. We speculate that a normal or supernormal contraction wave pushing bolus against resistance is the mechanism of dysphagia sensation in significant number of patients. Representations of distension and contraction, combined with objective measures of flow timing and distensibility are complementary to the current scheme of classifying esophageal motility disorders based solely on the characteristics of contraction phase of peristalsis. Better understanding of the distensibility of the bolus-containing segment of the esophagus during peristalsis will lead to the development of novel medical and surgical therapies in the treatment of dysphagia in significant number of patients.

Bolus flow and biomechanical properties of the esophageal wall during primary esophageal peristalsis: Effects of bolus viscosity and posture

BACKGROUND

Studies show that intraluminal impedance recordings of the esophagus allow one to measure the luminal distension during peristalsis, an important parameter for calculation of the biomechanical properties of esophageal wall. The goal was to determine the effect of subject posture and bolus viscosity on the biomechanical properties of esophageal wall, and the rate of bolus flow along the length of the esophagus during primary peristalsis.

METHODS

High-resolution manometry impedance recordings were obtained in 14 normal healthy subjects. Swallows of 10 ml saline and viscous bolus were recorded in the supine and Trendelenburg positions. User identified the region of interest, and a custom-designed software extracted parameters of interest such as bolus flow rate, esophageal wall tension, and esophageal wall distensibility in four equal segments of the esophagus.

KEY RESULTS

Bolus flow rate decreases along the length of the esophagus, being slowest in the distal esophagus. Bolus flow rate is smaller in the Trendelenburg position and with viscous bolus as compared with supine position and saline bolus. Esophageal wall tension is greater in the Trendelenburg position and with viscous bolus as compared with the supine position and saline bolus. The esophageal wall distensibility is larger in the distal as compared with proximal esophagus, which is true for both the saline and viscous bolus.

CONCLUSIONS & INFERENCES

We report, for the first time, bolus flow rate and biomechanical properties of the esophageal wall during swallow-induced primary peristalsis. Future studies may investigate biomechanical basis of esophageal motility disorders using the methodology described.

Rhythmic contraction but arrhythmic distension of esophageal peristaltic reflex in patients with dysphagia

Background

Reason for dysphagia in a significant number of patients remains unclear even after a thorough workup. Each swallow induces esophageal distension followed by contraction of the esophagus, both of which move sequentially along the esophagus. Manometry technique and current system of classifying esophageal motility disorders (Chicago Classification) is based on the analysis of the contraction phase of peristalsis.

Goal

Whether patients with unexplained dysphagia have abnormalities in the distension phase of esophageal peristalsis is not known.

Methods

Using Multiple Intraluminal esophageal impedance recordings, which allow determination of the luminal cross-sectional area during peristalsis, we studied patients with nutcracker esophagus (NC), esophagogastric junction outflow obstruction (EGJOO), and functional dysphagia (FD).

Results

Distension contraction plots revealed that swallowed bolus travels significantly faster through the esophagus in all patient groups as compared to normals. The luminal cross-sectional area (amplitude of distension), and the area under the curve of distension were significantly smaller in patients with NC, EGJOO, and FD as compared to normals. Bolus traverses the esophagus in the shape of an “American Football” in normal subjects. On the other hand, in patients the bolus flow was fragmented. ROC curves revealed that bolus flow abnormalities during peristalsis are a sensitive and specific marker of dysphagia.

Conclusion

Our findings reveal abnormality in the distension phase of peristalsis (a narrow lumen esophagus) in patients with dysphagia. We propose that the esophageal contraction forcing the swallowed bolus through a narrow lumen esophagus is the cause of dysphagia sensation in patients with normal contraction phase of peristalsis.

Esophageal Bolus Domain Pressure and Peristalsis Associated With Experimental Induction of Esophagogastric Junction Outflow Obstruction

Background/Aims

Intrabolus pressures are important for esophageal bolus transport and may detect obstructed bolus flow. This study measured the effect esophageal outflow obstruction experimentally induce by a leg-lift protocol.

Methods

Twenty-five gastroesophageal reflux disease patients referred for esophageal manometry and a normal motility diagnosis were included. Supine liquid swallows were tested. Leg-lift protocol generated esophageal outflow obstruction by increasing abdominal pressure. Esophageal pressure topography and intrabolus pressure metrics were calculated. These included, (1) mid-domain bolus distension pressure during esophageal emptying (DPE, mmHg) and (2) ramp pressure (mmHg/sec), generated by compression of the bolus between the peristaltic contraction and esophagogastric junction (EGJ).

Results

EGJ relaxation pressure was increased by leg-lift from 13 (11-17) to 19 (14-30) mmHg (P < 0.005) and distal contractile integral also increased from 1077 (883-1349) to 1620 (1268-2072) mmHg∙cm∙sec (P < 0.001) as a physiological response to obstruction. All bolus pressures were increased by leg lift; DPE increased from 17 (15-20) to 27 (19-32) mmHg (P < 0.001), and ramp pressure increased from 3 (1-4) to 5 (2-9) mmHg/sec (P < 0.05).

Conclusion

Measuring pressures within the intrabolus domain can quantify changes related to obstruction to outflow and may serve as adjunct measures for confirming a diagnosis EGJ outflow obstruction.

Distension-contraction profile of peristalsis in patients with nutcracker esophagus

INTRODUCTION

High amplitude peristaltic esophageal contractions, that is, nutcracker esophagus, were originally described in association with "angina-like pain" of esophageal origin. However, significant number of nutcracker patients also suffer from dysphagia. High-resolution esophageal manometry (HRM) assesses only the contraction phase of peristalsis. The degree of esophageal distension during peristalsis is a surrogate of relaxation and can be measured from the intraluminal esophageal impedance measurements.

AIMS

Determine the amplitude of distension and temporal relationship between distension and contraction during swallow-induced peristalsis in nutcracker patients.

METHODS

HRM impedance (HRMZ) studies were performed and analyzed in 24 nutcracker and 30 normal subjects in the Trendelenburg position. A custom-built software calculated the numerical data of the amplitudes of distension and contraction, the area under the curve (AUC) of distension and contraction, and the temporal relationship between distension and contraction.

RESULTS

In normal subjects, the distension peaks similar to contraction traverse sequentially the esophagus. The amplitude of contraction is greater in the nutcracker esophagus but the amplitude of distension and area under the curve of distension are smaller in patients compared to controls. Distension peaks are aligned closely with contraction in normal subjects, but in patients, the bolus travels faster to the distal esophagus, resulting in a smaller time interval between the onset of swallow and distension peak. Receiver operative characteristics (ROC) curve reveals high sensitivity and specificity of the above parameters in patients.

CONCLUSION

Abnormalities in the distension phase of peristalsis are a possible mechanism of dysphagia in patients with nutcracker esophagus.

Effects of remifentanil on pharyngeal swallowing and esophageal motility: no impact of different bolus volumes and partial antagonism by methylnaltrexone

Remifentanil impairs swallowing, and disturbed accommodation to bolus volume may be one of the underlying causes. It is not fully understood whether remifentanil-induced swallowing dysfunction is mediated by peripheral or central mechanisms. So, this study aimed to investigate if remifentanil-induced swallowing dysfunction is dependent on the bolus volume and whether the effect of remifentanil could be counteracted by methylnaltrexone, a peripherally acting opioid antagonist. Nineteen healthy volunteers were included in this double-blinded, randomized, placebo-controlled, crossover study. Study participants received target-controlled remifentanil infusions and placebo infusions in a randomized order. Methylnaltrexone was administered by intravenous injection of doses of 0.3 mg/kg. Recordings of pressure and impedance data were acquired using a combined manometry and impedance solid-state catheter. Data were analyzed from three series of bolus swallows, baseline, during study medication exposure, and 15 min after methylnaltrexone. Remifentanil induced significant effects on multiple pharyngeal and esophageal function parameters. No significant differences in remifentanil-induced swallowing dysfunction related to different bolus volumes were found. Pharyngeal effects of remifentanil were not significantly counteracted by methylnaltrexone, whereas on the distal esophageal level, effects on distension pressures were counteracted. Changes in pharyngeal and esophageal pressure flow variables were consistent with previous results on remifentanil-induced swallowing dysfunction and uniform across all bolus volumes. The effects of remifentanil on the pharyngeal level and on the proximal esophagus appear to be predominantly centrally mediated, whereas the effects of remifentanil on the distal esophagus may be mediated by both central and peripheral mechanisms.NEW & NOTEWORTHY In this randomized controlled trial, we used the "Swallow Gateway" online platform to analyze the effects of remifentanil on pharyngeal and esophageal swallowing. It is not fully understood whether remifentanil-induced swallowing dysfunction is mediated by peripheral or central mechanisms. By using methylnaltrexone, we demonstrated that effects of remifentanil on pharyngeal swallowing were predominantly centrally mediated, whereas its effects on the distal esophagus may be mediated by both central and peripheral mechanisms.

Novel gel bolus to improve impedance-based measurements of esophageal cross-sectional area during primary peristalsis

INTRODUCTION

Intraluminal esophageal impedance (ILEE) has the potential to measure esophageal luminal distension during swallow-induced peristalsis in the esophagus. A potential cause of inaccuracy in the ILEE measurement is the swallow-induced air in the bolus.

AIM

Compare a novel gel bolus to the current alternatives for the measurement of impedance-based luminal distension (cross-sectional area, CSA) during primary peristalsis.

METHODS

12 healthy subjects were studied using high-resolution impedance manometry (HRMZ) and concurrently performed intraluminal ultrasound (US) imaging of the esophagus. Three test bolus materials were used: 1) novel gel, 2) 0.5 N saline, and 3) commercially available Diversatek EFTV viscous. Testing was performed in the supine and Trendelenburg (-15°) positions. US imaging assessed air in the bolus and luminal CSA. The Nadir impedance values were correlated to the US measured CSA. A custom Matlab software was used to assess the bolus travel times and impedance-based luminal CSA.

RESULTS

The novel gel bolus had the least amount of air in the bolus during its passage through the esophagus, as assessed by US image analysis. The novel gel bolus in the supine and Trendelenburg positions had the best linear fit between the US measured CSA and nadir impedance value (R²  = 0.88 & R²  = 0.90). The impedance-based calculation of the CSA correlated best with the US measured CSA with the use of the novel gel bolus.

CONCLUSION

We suggest the use of novel gel to assess distension along with contraction during routine clinical HRM testing.