Shezhang Lin

The effect of hiatus hernia on gastro-oesophageal junction pressure

BACKGROUND Hiatus hernia and lower oesophageal sphincter hypotension are often viewed as opposing hypotheses for gastro-oesophageal junction incompetence. AIMS To examine the interaction between hiatus hernia and lower oesophageal sphincter hypotension. METHODS In seven normal subjects and seven patients with hiatus hernia, the squamocolumnar junction and intragastric margin of the gastro-oesophageal junction were marked with endoscopically placed clips. Axial and radial characteristics of the gastro-oesophageal junction high pressure zone were mapped relative to the hiatus and clips during concurrent fluoroscopy and manometry. Responses to inspiration and abdominal compression were also analysed. RESULTS In normal individuals the squamocolumnar junction was 0.5 cm below the hiatus and the gastro-oesophageal junction high pressure zone extended 1.1 cm distal to that. In those with hiatus hernia, the gastro-oesophageal junction high pressure zone had two discrete segments, one proximal to the squamocolumnar junction and one distal, attributable to the extrinsic compression within the hiatal canal. Inspiration and abdominal compression mainly augmented the distal one. Simulation of hernia reduction by algebraically summing the proximal segment pressures with the hiatal canal pressures restored normal maximal pressure, radial asymmetry, and dynamic responses of the gastro-oesophageal junction. CONCLUSIONS Hiatus hernia reduces lower oesophageal sphincter pressure and alters its dynamic responsiveness by spatially separating pressure components derived from the intrinsic lower oesophageal sphincter and the extrinsic compression of the oesophagus within the hiatal canal.

Pharyngeal Clearance During Swallowing: A Combined Manometric and Videofluoroscopic Study

The deglutitive pharyngeal contraction was analyzed using simultaneous videofluoroscopic and manometric studies of eight volunteers. Anterior, posterior, and longitudinal movements of the pharyngeal surfaces, relative to the cervical vertebrae, were measured during swallows of 5 and 10 mL of liquid barium. Profound pharyngeal shortening during bolus transit through the pharynx eliminated access to the larynx and elevated the upper esophageal sphincter to within 1.5 cm of the retrolingual pharynx. Bolus head movement through the pharynx preceded the propagated pharyngeal contraction and registered manometrically as a slight intrabolus pressure before the major pressure complex. Contraction in the horizontal plane began after bolus head transit and culminated with stripping of the bolus tail through the pharynx. Prolonged upper sphincter opening with the larger-volume swallows resulted from a delayed onset rather than altered propagation of the horizontal pharyngeal contraction. It is concluded that the propagated pharyngeal contraction facilitates pharyngeal clearance but has a minimal role in the process of bolus propulsion during swallowing. The propagated contraction works in concert with profound pharyngeal shortening to minimize hypopharyngeal residue after a swallow.

Deglutitive tongue action: Volume accommodation and bolus propulsion

BACKGROUND Swallow function is best analyzed in components because discrete component failure may be compensated for with devised maneuvers, postures, or biofeedback techniques. The present investigation examined normal deglutitive tongue function. METHODS Biplane videofluoroscopy synchronized with intraluminal manometry was performed in eight volunteers. Tongue surface motion was characterized as centripetal or centrifugal along seven equiangular rays emanating from the tongue center during 1-, 5-, 10-, and 20-mL swallows. RESULTS The tongue perimeter remained in contact with the alveolar ridge while the central groove exhibited centripetal and subsequent centrifugal motion that, in conjunction with the pharyngeal walls, created an oropharyngeal propulsive chamber and then expelled that chambers contents into the hypopharynx. Intrabolus propulsive pressure was generated when the initially expansive propulsive chamber volume contracted to the test bolus volume. Because pharyngeal chamber action cycle timing was relatively constant among bolus volumes, vigorous expulsion occurred with large volumes but relatively delayed, sluggish expulsion occurred with smaller volumes. CONCLUSIONS Deglutitive tongue functions include bolus containment, volume accommodation, and the major contributor to bolus propulsion.

Timing, propagation, coordination, and effect of esophageal shortening during peristalsis

BACKGROUND & AIMS Minimal information exists on the characteristics and effect of esophageal shortening during peristalsis in the human esophagus. The aim of this study was to quantify esophageal shortening during peristalsis and determine the relationship between shortening, circular muscle contraction, and generation of propulsive force. METHODS Ten volunteers had three metal clips endoscopically affixed at the squamocolumnar junction and 4.5 and 9 cm proximal to it, defining proximal and distal segments in the lower esophagus. A strain gauge manometer was positioned within the proximal segment along with a traction force sensing balloon. Axial clip movement was assessed with concurrent manometry and videofluoroscopy during swallowing to examine the determinants of propulsive force. RESULTS Esophageal shortening was coordinated with circular muscle contraction such that each propagated distally as overlapping segments of contraction at a velocity of about 2.5 cm/s. Propulsive force within the proximal segment occurred after shortening, during the circular muscle contraction, with the magnitude of propulsive force correlated with the degree of distal shortening. CONCLUSIONS (1) Both circular and longitudinal esophageal muscle contraction occur as propagating segments during peristalsis, with the longitudinal muscle contraction leading the circular muscle. (2) Propulsive force occurs during proximal circular and distal longitudinal muscle contraction.

Attenuation of esophageal shortening during peristalsis with hiatus hernia

BACKGROUND & AIMS Minimal quantitative information exists on esophageal shortening during peristalsis in the human esophagus. The aim of this study was to ascertain the effect of hiatus hernia on longitudinal muscle-mediated peristaltic esophageal shortening. METHODS Seven volunteers and 11 patients with hiatal hernia had metal clips endoscopically affixed at the squamocolumnar junction and 3-5 cm proximal to it (n = 11). Location of the lower esophageal sphincter and axial clip movement were assessed using concurrent manometry and videofluoroscopy during barium swallows in a supine and upright posture with and without abdominal compression. RESULTS Three subject groups were defined by the proximity of the squamocolumnar junction to the diaphragmatic hiatus: group 1, < or = 0 cm; group 2, between 0 and 2 cm; and group 3, > or = 2 cm. Peristaltic esophageal shortening was progressively diminished, re-elongation progressively prolonged, and the degree of contraction observed in the distal esophageal segment reduced with progressive degree of hiatus hernia. There was minimal mobility of the squamocolumnar junction relative to the hiatus with posture or abdominal compression. CONCLUSIONS Longitudinal muscle contraction during peristalsis normally causes transient elevation of the squamocolumnar junction above the diaphragm. Esophageal shortening during primary peristalsis is reduced with increasing degree of hiatus hernia, suggesting that there is diminished opposition of longitudinal muscle contraction from the phrenoesophageal attachments.

Impact of fundoplication on bolus transit across esophagogastric junction

This study analyzed the effect of fundoplication on the mechanics of liquid and solid bolus transit across the esophagogastric junction (EGJ). The squamocolumnar junction was endoscopically clipped in seven controls, seven hiatal hernia patients, and seven patients after laparoscopic Nissen fundoplication. Concurrent manometry and fluoroscopy were done during swallows of liquid barium and a 13-mm-diameter marshmallow. The EGJ opening, pressure gradients, transit efficacy, and axial motion were measured. The axial motion of the EGJ was reduced in the fundoplication and hiatal hernia patients. The opening dimensions at the squamocolumnar junction were similar among groups, but in each case the constriction limiting flow to the stomach was at the hiatus and this was substantially narrowed with fundoplication. As a result, liquid intrabolus pressure was increased and marshmallow transit frequently required multiple swallows. We conclude that fundoplication limits the axial mobility of the EGJ and leads to a restricted hiatal opening. These alterations decrease the efficacy of solid and liquid transit into the stomach and are potential causes of dysphagia in this population.This study analyzed the effect of fundoplication on the mechanics of liquid and solid bolus transit across the esophagogastric junction (EGJ). The squamocolumnar junction was endoscopically clipped in seven controls, seven hiatal hernia patients, and seven patients after laparoscopic Nissen fundoplication. Concurrent manometry and fluoroscopy were done during swallows of liquid barium and a 13-mm-diameter marshmallow. The EGJ opening, pressure gradients, transit efficacy, and axial motion were measured. The axial motion of the EGJ was reduced in the fundoplication and hiatal hernia patients. The opening dimensions at the squamocolumnar junction were similar among groups, but in each case the constriction limiting flow to the stomach was at the hiatus and this was substantially narrowed with fundoplication. As a result, liquid intrabolus pressure was increased and marshmallow transit frequently required multiple swallows. We conclude that fundoplication limits the axial mobility of the EGJ and leads to a restricted hiatal opening. These alterations decrease the efficacy of solid and liquid transit into the stomach and are potential causes of dysphagia in this population.

Shape, volume, and content of the deglutitive pharyngeal chamber imaged by ultrafast computerized tomography.

BACKGROUND Conventional radiographic techniques image only the silhouettes of the deglutitive pharyngeal chamber. This study aimed to accurately image the horizontal plane shape and content of the pharynx during swallowing. METHODS Dynamic computerized tomography images of the pharynx were obtained at the rate of 17 per second during swallowing. Multiple adjacent levels were imaged in eight subjects and a single level was scanned in four subjects during swallows of varied volume. Images were analyzed for area, volume, and the bolus fraction of the deglutitive pharyngeal chamber. RESULTS The deglutitive chamber enlarged to approximately 24 mL (during tongue loading) compared with a preswallow pharyngeal volume averaging 15 mL. Throughout the 10 mL swallows, the bolus occupied less than 30% of the lumen regardless of axial level. The bolus fraction of the deglutitive chamber increased with swallow volume, as did the dimensions of the upper esophageal sphincter and the bolus velocity through the upper esophageal sphincter. CONCLUSIONS The deglutitive pharyngeal chamber was typically approximately 15 mL > the bolus volume, implying that an obligatory 15 mL of air was swallowed under these test conditions. Most swallowed air originated as air trapped within the pharynx and larynx as the oropharynx was sealed from above and below.

Dynamic reconstruction of the orophanryngeal swallow using computer based animation

The oropharyngeal swallow was modeled with computer based animation using data from biplane videofluorographic and dynamic CT images of 10 ml liquid swallows of a volunteer subject. Tracings of oropharyngeal structures from synchronized, magnification adjusted, images of the posterior-anterior, lateral, and cross-sectional planes were aligned in three dimensions with graphics animation software. Twenty oropharyngeal configurations were created at 1/15 second intervals to dynamically illustrate the swallow. These three-dimensional reconfigurations could be sequenced into an animation routine. Software analysis of the model permitted quantification of structural movement and intrapharyngeal volume across time. Such analyses can be used to detail both the efficacy of individual functional elements of the swallow as well as global pump function. It is hoped that modeling the oropharyngeal swallow will be useful to analyze mechanisms of dysphagia and the mechanics of compensatory therapeutic strategies.

Pressure morphology of the gastroesophageal junction after fundoplication: How normal is it

Though effective in resolving esophagitis, fundoplication (FP) can impair belching, a venting mechanism that requires both a relaxed sphincter an d that intragastric pressure exceed extrasphincteric pressure. To better understand this limitation, we compared gastroesophageal junction (GEJ) pressure morphology after FP to that of normal volunteers (N1) and hiatal hernia (HH) patients. Methods: Metal clips were placed endoscopically to mark the intragastric margin of the GEJ and squamocolumnar junction (SCJ) in 7 Nls, 7 HH patients, and 7 patients after FP. GEJ pressure (0=atmospheric) referenced to the clips and hiatus was measured during concurrent videofluoroscopy and mechanized pull through of an 8-lumen manometer with radiopaque side holes at the same axial level but 45 ° apart radially. Subdiaphragmatic length (SDL) of the GEJ (shaded area in figure) was that distal to the hiatal canal, as localized in HH patients. Pull throughs were done during endexpiration, deep inspiration, and abdominal compression (AC) with a binder inflated to 100 mmHg. Results: Axial position of the SCJ was restored post-FP, but GEJ pressure morphology of each group was distinct (Figure & Table, All data mean -+ SE).