Biomedical subjects

J G Brasseur

Publications and source records attributed to J G Brasseur.

At least 19 recordsLinked to original sources

PubMed2005

Measuring EGJ opening patterns using high resolution intraluminal impedance.

The aim of this study was to adapt impedance methodology to study esophagogastric junction (EGJ) sphincter opening and compare opening patterns of the EGJ during deglutitive LES relaxation (dLESR) and transient LES relaxation (tLESR). We studied eight healthy subjects with a novel 12-lumen combined impedance/manometry catheter, the main element of which was a 6 cm sleeve sensor with six side hole sensors and six impedance rings spaced at 1 cm increments along its length. Subjects underwent an air infusion protocol after standard assessment and data tracings and isocontour plots were analysed to assess opening characteristics of the EGJ during dLESRs and tLESRs. Our results revealed that during dLESR the opening pattern was top to bottom, occurred in 0-2.7 s and in 29 of 35 (83%) cases the leading edge of the bolus was liquid. Opening during tLESR began between -7.8 and +8.6 s relative to the onset of nadir LES relaxation. The opening pattern during tLESR was bottom to top, occurred in 0-7.7 s, and in 22 of 29 (76%) the leading edge was liquid. These results support that impedance monitoring can be adapted to identify sphincter opening, to distinguish sphincter opening from sphincter relaxation, and to determine luminal contents during the opening period.

Adult↗

PubMed2004

High-resolution manometry predicts the success of oesophageal bolus transport and identifies clinically important abnormalities not detected by conventional manometry.

BACKGROUND AND AIMS: High-resolution manometry (HRM) is a recent development in oesophageal measurement; its value in the clinical setting remains a matter of controversy. (i) We compared the accuracy with which bolus transport could be predicted from conventional manometry and HRM. (ii) The clinical value of HRM was assessed in a series of patients with endoscopy-negative dysphagia in whom conventional investigations had been non-diagnostic. METHOD: (i) Control subjects and patients with endoscopy-negative dysphagia underwent concurrent HRM and video-fluoroscopy. Ninety-five records were reviewed using HRM with spatiotemporal plot and conventional line plots of the pressure data derived from the same recording. (ii) The HRM and notes of patients with endoscopy-negative dysphagia and abnormal bolus transport were analysed to identify additional information provided by the new technique. RESULTS: (i) Receiver operating characteristic analysis demonstrated that HRM predicts the presence of abnormal bolus transport more accurately than conventional manometry. (ii) HRM identified clinically important motor dysfunction not detected by manometry and radiography. These included localized disturbances of peristalsis and abnormal movement of the lower oesophageal sphincter during oesophageal spasm. CONCLUSION: The HRM predicts bolus movement more accurately than conventional manometry and identifies clinically relevant oesophageal dysfunction not detected by other investigations including conventional manometry.

Adult↗

PubMed2002

Distinct patterns of oesophageal shortening during primary peristalsis, secondary peristalsis and transient lower oesophageal sphincter relaxation.

This study characterized oesophageal shortening during secondary peristalsis and transient lower oesophageal sphincter relaxation (TLOSR) in an attempt to determine its contribution to the opening mechanism. Eight healthy subjects (four males, 26 +/- 1 years) had metal clips affixed at 0, +3, and +8 cm relative to the squamocolumnar junction (SCJ), defining two distal oesophageal segments. Axial clip movement was assessed with concurrent videofluoroscopy and manometry during primary peristalsis, secondary peristalsis and TLOSR. Clip-defined oesophageal segment length change was measured at 0.5-s intervals. The magnitude of the most distal segment shortening was least with TLOSR, greatest with primary peristalsis and intermediate with secondary peristalsis. Conversely, maximal overall oesophageal shortening during TLOSR, evidenced by SCJ movement, was similar to that during primary peristalsis. In 3/12 TLOSRs, the moment of LOS opening and gas reflux was optimally imaged; SCJ excursion was 0.3 +/- 0.1 cm prior to LOS opening and 1.4 +/- 0.7 cm immediately after gas reflux. The segmental pattern of oesophageal shortening was distinct during primary peristalsis, secondary peristalsis and TLOSR. During TLOSR, significant elevation of the SCJ occurred only after LOS opening, suggesting that this was a consequence of oesophageal distension induced by gas reflux rather than a component of the opening mechanism.

Adult↗

PubMed2001

Local longitudinal muscle shortening of the human esophagus from high-frequency ultrasonography.

We analyzed local longitudinal shortening by combining concurrent ultrasonography and manometry with basic principles of mechanics. We applied the law of mass conservation to quantify local axial shortening of the esophageal wall from ultrasonically measured cross-sectional area concurrently with measured intraluminal pressure, from which correlations between local contraction of longitudinal and circular muscle are inferred. Two clear phases of local longitudinal shortening were observed during bolus transport. During luminal filling by bolus fluid, the muscle layer distends and the muscle thickness decreases in the absence of circular or longitudinal muscle contraction. This is followed by local contraction, first in longitudinal muscle, then in circular muscle. Maximal longitudinal shortening occurs nearly coincidently with peak intraluminal pressure. Longitudinal muscle contraction begins before and ends after circular muscle contraction. Larger longitudinal shortening is correlated with higher pressure amplitude, suggesting that circumferential contractile forces are enhanced by longitudinal muscle shortening. We conclude that a peristaltic wave of longitudinal muscle contraction envelops the wave of circular muscle contraction as it passes through the middle esophagus, with peak longitudinal contraction aligned with peak circular muscular contraction. Our results suggest that the coordination of the two waves may be a physiological response to the mechanical influence of longitudinal shortening, which increases contractile force while reducing average muscle fiber tension by increasing circular muscle fiber density locally near the bolus tail.

Deglutition↗

PubMed2001

Pressure-geometry relationship in the antroduodenal region in humans.

Understanding of the control mechanisms underlying gastric motor function is still limited. The aim of the present study was to evaluate antral pressure-geometry relationships during gastric emptying slowed by intraduodenal nutrient infusion and enhanced by erythromycin. In seven healthy subjects, antral contractile activity was assessed by combined dynamic magnetic resonance imaging and antroduodenal high-resolution manometry. After intragastric administration of a 20% glucose solution (750 ml), gastric motility and emptying were recorded during intraduodenal nutrient infusion alone and, subsequently, combined with intravenous erythromycin. Before erythromycin, contraction waves were antegrade (propagation speed: 2.7 +/- 1.7 mm/s; lumen occlusion: 47 +/- 14%). Eighty-two percent (51/62) of contraction waves were detected manometrically. Fifty-four percent of contractile events (254/473) were associated with a detectable pressure event. Pressure and the degree of lumen occlusion were only weakly correlated (r(2) = 0.02; P = 0.026). After erythromycin, episodes of strong antroduodenal contractions were observed. In conclusion, antral contractions alone do not reliably predict gastric emptying. Erythromycin induces strong antroduodenal contractions not necessarily associated with fast emptying. Finally, manometry reliably detects ~80% of contraction waves, but conclusions from manometry regarding actual contractile activity must be made with care.

Duodenum↗

PubMed2001

Space-time pressure structure of pharyngo-esophageal segment during swallowing.

We applied high-resolution manometry with spatiotemporal data interpolation and simultaneous videofluoroscopy to normal pharyngeal swallows to correlate specific features in the space-time intraluminal pressure structure with physiological events and normal deglutitive transsphincteric bolus flow to define normal biomechanical properties of the pharyngo-esophageal (PE) segment. Pressures were recorded by microperfused catheter, and the two-dimensional space-time data sets were plotted as isocontours. On these were superimposed bolus trajectories, anatomic segment movements, and hyo-laryngeal trajectories from concurrent videofluoroscopy. Correlation of the highly reproducible space-time-pressure structure with radiographic images confirmed that primary deglutitive PE segment functions (pressure profile, laryngeal elevation, axial sphincter motion, timing of relaxation, contraction) are accurately discernible from single isocontour pressure visualization. Pressure during bolus flow was highly dependent on axial location within PE segment and time instant. The intrabolus pressure domain, corresponding to the space-time region between bolus head and tail trajectories, demonstrated significant bolus volume dependence. High-resolution manometry accurately, comprehensively, and highly reproducibly depicts the PE segment space-time-pressure structure and specific physiological events related to upper esophageal sphincter opening and transsphincteric flow during normal swallowing. Intrabolus pressure variations are highly dependent on position within the PE segment and time.

Adult↗

PubMed2000

Bolus transit assessed by an esophageal stress test in postfundoplication dysphagia.

INTRODUCTION: Dysphagia is common after Nissen fundoplication but the relationship between dysphagia and bolus transit is poorly defined. This study compared bolus transit of fundoplication patients to normal individuals. METHODS: Twelve fundoplication patients and 20 healthy volunteers rated their ability to swallow eight bolus consistencies from no difficulty (0) to extreme difficulty (3) to compute a dysphagia score (range = 0-24). A 16-lumen manometric assembly was positioned across the esophagogastric junction (EGJ) and subjects were imaged fluoroscopically in a supine posture while swallowing 5 cc liquid barium and a 5-cc marshmallow-like viscoelastic barium bolus. Videofluoroscopic images were analyzed for total esophageal transit time and the fraction of time required to cross the EGJ. Manometric tracings were analyzed for the intrabolus pressure proximal to the EGJ, intragastric pressure, and distal peristaltic amplitude for each bolus. RESULTS: Dysphagia scores for fundoplication patients were significantly higher (7.3 +/- 5.1, range = 1-17) than for normals (0.5 +/- 0.6, range = 0-2). This correlated with longer total transit times for liquids and solids (r = 0.60, P < 0.01) and a greater percentage of transit time attributable to the EGJ transit. Retrograde flow at the EGJ (escape of bolus proximally up the esophagus) and peristaltic dysfunction were more frequent in fundoplication patients. However, no differences existed in manometric parameters between groups. CONCLUSIONS: Fundoplication impairs both liquid and solid esophageal bolus transit. Dysphagia perceived by fundoplication patients correlated with increased transit time, particularly across the EGJ. Combined quantitative evaluation with manometry and fluoroscopy reveals functional defects in fundoplication subjects, which are not evident by either modality alone.

Adult↗

PubMed2000

Relative contributions of "pressure pump" and "peristaltic pump" to gastric emptying.

The relative contributions to gastric emptying from common cavity antroduodenal pressure difference ("pressure pump") vs. propagating high-pressure waves in the distal antrum ("peristaltic pump") were analyzed in humans by high-resolution manometry concurrently with time-resolved three-dimensional magnetic resonance imaging during intraduodenal nutrient infusion at 2 kcal/min. Gastric volume, space-time pressure, and contraction wave histories in the antropyloroduodenal region were measured in seven healthy subjects. The subjects fell into two distinct groups with an order of magnitude difference in levels of antral pressure activity. However, there was no significant difference in average rate of gastric emptying between the two groups. Antral pressure history was separated into "propagating high-pressure events" (HPE), "nonpropagating HPEs," and "quiescent periods." Quiescent periods dominated, and average pressure during quiescent periods remained unchanged with decreasing gastric volume, suggesting that common cavity pressure levels were maintained by increasing wall muscle tone with decreasing volume. When propagating HPEs moved to within 2-3 cm of the pylorus, pyloric resistance was found statistically to increase with decreasing distance between peristaltic waves and the pylorus. We conclude that transpyloric flow tends to be blocked when antral contraction waves are within a "zone of influence" proximal to the pylorus, suggesting physiological coordination between pyloric and antral contractile activity. We further conclude that gastric emptying of nutrient liquids is primarily through the "pressure pump" mechanism controlled by pyloric opening during periods of relative quiescence in antral contractile wave activity.

Adult↗

PubMed1998

In situ measurements of Doppler power vs. flow turbulence intensity in red cell suspensions.

Whereas previous studies have shown that ultrasonic backscatter and Doppler power from blood are affected by flow turbulence, turbulence level has only been inferred from the flow Reynolds number and not directly measured. In this study, both ultrasonic Doppler power and flow turbulence intensity were measured in situ to quantify the relationship between Doppler power and flow turbulence. Three grid meshes of different geometries were used in a steady-flow mock loop to generate controlled levels of flow turbulence in porcine red blood cell saline suspensions. Doppler power was measured by a 10-MHz PW Doppler flowmeter, and the turbulence intensity by using constant-temperature hot film anemometry. We showed that Doppler power is affected by turbulence and hematocrit in a complex way. At a fixed hematocrit, Doppler power increases nonlinearly with turbulence intensity and, at fixed turbulence intensity, Doppler power peaks at an optimal hematocrit level that increases with turbulence level. The shape factor, introduced by Lucas and Twersky (1987) to take into account effects of shape and orientation of the scatterers in a dense distribution of small and tenuous scatterers, was estimated by fitting the experimental data to the theoretical model. The results indicate that shape factor decreases with increasing turbulence intensity.

Animals↗

PubMed1998

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.

Adult↗

PubMed1995

The phrenic ampulla: distal esophagus or potential hiatal hernia?

The mechanics of phrenic ampullary emptying were analyzed to determine whether this structure functions in a manner similar to the tubular esophagus or a hiatal hernia. Simultaneous videofluoroscopy and intraluminal manometry of the gastroesophageal junction were done during barium swallows in 18 normal volunteers. Esophageal emptying was studied without any external influences, during abdominal compression with a cuff inflated to 100 mmHg, during a Müller maneuver, and after medication with atropine. The key finding of the study was that ampullary emptying was distinct from esophageal bolus transport in several ways: the propagation velocity of the clearing wave was slower, the maximal contact pressures achieved after luminal closure were lower and unaffected by atropine or outflow obstruction, and ampulary emptying was driven by a hydrostatic pressure difference between the ampulla and stomach rather than by a peristaltic contraction. Increased bolus volume slightly enlarged the ampulla. Taken together, these findings suggest that ampullary emptying occurs, in part, as a result of the restoration of esophageal length (presumably by tension from the phrenoesophageal membrane) rather than as a result of an aborally propagated contraction. As such, a normal phrenic ampulla is analogous to a small reducing hiatal hernia. We speculate that overt hernia formation occurs as a result of progressive degeneration of the phrenoesophageal membrane.

Adult↗

PubMed1994

Analyses of normal and abnormal esophageal transport using computer simulations.

Mathematical modeling and computer simulations are combined with concurrent manometric and videofluoroscopic data to analyze the contractile behavior of the esophageal wall during normal and abnormal esophageal bolus transport. The study focuses on axial variations in intraluminal pressure in relationship to deformations of the esophageal wall during the transport process. Four case studies of esophageal bolus transport described by Kahrilas et al. (Gastroenterology 94: 73-80, 1988), one normal and three abnormal, are analyzed in detail by capturing the major elements of both the videofluoroscopic and concurrent manometric data in the mathematical model. In all cases a strong correlation between the deformations of the luminal wall and the axial variations of intraluminal pressure is observed. Simulation of normal bolus transport shows that, whereas only gentle variations in intrabolus pressure occur in the main body of the bolus due to weak frictional forces there, large frictional forces force a rapid rise in pressure near the bolus tail induced by circular muscle squeeze. Of particular interest is the analysis of incomplete clearance of bolus fluid in the aortic arch region. The only physically correct model consistent both with the videofluoroscopic and the manometric data implies the existence of two separate contraction waves, one above and one below the transition zone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Mechanical studies of the esophageal function.

The discussion centers on the use of mechanical principles, mathematical modeling, and concurrent manometric and videofluoroscopic data to study the esophageal function. Basic principles of mechanics indicate that intrabolus pressure must be distinguished from the direct contractile squeeze of the circular muscle on the manometric assembly. Because these two regions are mechanically distinct, pressure amplitude is not a proper indicator of the forces characterizing esophageal bolus transport. In the application of computer simulations to the transport of a fluid bolus through the aortic arch regions, it was discovered that separate contraction waves must exist in the upper and lower esophageal segments when bolus retention occurs. Through detailed analysis of enhanced concurrent manometric and videofluoroscopic data in human volunteers, we have found that a dual-wave characteristic across the transition zone is a normal reflection of the change in muscle types, each muscle type producing a separate contraction wave. In normal transport, these two contraction waves are properly coordinated spatially and temporally. However, during bolus retention, a mismatch in space and time between these two waves takes place. Analysis suggests that this mismatch is neurological rather than histological in origin, and occurs primarily within the lower smooth-muscle segment.

Deglutition↗

PubMed1993

Determinants of intrabolus pressure during esophageal peristaltic bolus transport.

Previous manometric studies of esophageal fluid bolus transport in humans have generally ignored the hydrodynamic distinction between intrabolus pressure and pressure within the lumen-occluded, contracting esophageal segment. In this study we obtained concurrent esophageal videofluoroscopic and intraluminal manometric recordings in supine normal volunteers using different bolus volumes and viscosities and abdominal compression. Intrabolus pressure increased with bolus volume, viscosity, and abdominal compression. Esophageal diameter increased with larger bolus volumes, and this increase was correlated with increases in intrabolus pressure. Intrabolus pressure was highest in the bolus tail. Peak intraluminal pressures > 20 mmHg above basal intrabolus pressure almost invariably were associated with effective peristalsis, whereas values of this pressure differential < 20 mmHg frequently were associated with ineffective peristalsis and retrograde bolus escape. Intrabolus pressure can serve as an important indicator of the forces resisting peristaltic transport and the occurrence of ineffective bolus transport.

Abdomen↗

PubMed1992

Viscosity measurements of barium sulfate mixtures for use in motility studies of the pharynx and esophagus.

Detailed viscosity measurements have been made of barium sulfate mixtures over a wide range of viscosities for use in radiography of the esophagus, stomach, and duodenum. A new methodology was developed for more accurate estimation of viscosity in non-Newtonian fluids in conventional cylinder-type viscometers. As base cases, the variation of viscosity with shear rate was measured for standard commercial mixes of e.z.hd (250% w/v) and a diluted mixture of liquid e.z.paque (40% w/v). These suspensions are strongly shear thinning at low shear rates. Above about 3s-1 the viscosity is nearly constant, but relatively low. To increase the viscosity of the barium sulfate mixture, Knott's strawberry syrup was mixed to different proportions with e.z.hd powder. In this way viscosity was systematically increased to values 130,000 times that of water. For these mixtures the variation of viscosity with temperature, and the change in mixture density with powder-syrup ratio are documented. From least-square fits through the data, simple mathematical formulas are derived for approximate calculation of viscosity as a function of mixture ratio and temperature. These empirical formulas should be useful in the design of "test kits" for systematic study for pharyngeal and esophageal motility, and clinical analysis of motility disorders as they relate to bolus consistency.

Barium Sulfate↗

PubMed1991

Interpretation of intraluminal manometric measurements in terms of swallowing mechanics.

A unified discussion of the mechanics of the swallowing process, and its interpretation through manometric measurements of intraluminal pressure, are presented in this paper. The goals of the discussions are to provide the reader with basic knowledge of pharyngeal, esophageal, and sphincter mechanics; to relate the mechanical processes to intraluminal pressure recordings; and to clarify the relationship between intraluminal pressure and esophageal muscle contractile behavior. The esophageal phase of bolus transport, in particular, is discussed in some detail due to the relatively simple geometry and the straightforward description of peristalsis and muscle mechanics in this region. Several important issues are emphasized in the discussion. For example, pressure variation within a static bolus is fundamentally different from that within a moving bolus. Manometric recordings must be interpreted accordingly. The importance of differentiating between "hydrodynamic pressure," which is pressure measured within a fluid bolus, and "contact pressure," which is the direct squeeze of the luminal wall on the manometric port in a region devoid of bolus fluid, is discussed in some detail. We argue that pressure "amplitude" does not, in principle, give any indication of the forces required to drive the fluid bolus forward. What should be sought is the variation of intrabolus pressure relative to the contact pressure, particularly during periods in which the contractile segment fails to obliterate the esophageal lumen. Examples of intraluminal pressure recording in the esophagus, using manometry and mathematical models, are presented to demonstrate both the possibilities and the difficulties of interpreting manometric recordings in the absence of concurrent radiographic imaging. We discover that in regions of nearly complete luminal closure, the pressure signature and bolus geometry are strongly coupled during peristaltic transport, providing the possibility that in these regions quantitative measures of muscle performance might be developed without the need for radiographic imaging. On the other hand, the ambiguity in the interpretation of manometric recordings that often accompanies dysphagic conditions suggests that as more sophisticated interpretations are sought, manometry concurrent with radiography will play a more prominent role in patient evaluation.

Biophysical Phenomena↗

PubMed1991

Effects of stanniectomy and experimental hypercalcemia on plasma calcium levels and calcium influx in American eels, Anguilla rostrata, LeSueur.

Intraperitoneal injection of CaCl2 in intact, sham-stanniectomized, and stanniectomized American eels, Anguilla rostrata (LeSueur), resulted in a rapid elevation of plasma calcium level which was more marked and of longer duration in the stanniectomized eels. The same treatment reduced whole body calcium influx (JinCa2+) in the intact and sham-stanniectomized groups for the first but not the second of two 4 hr flux periods. The same treatment did not affect JinCa2+ in the stanniectomized eels. We conclude that calcium loading in eels with intact stannius corpuscles (CS) results in the release of a CS hormone (stanniocalcin) which inhibits the uptake of calcium from the environment and that this facilitates the return to normocalcemia. These data provide direct evidence for a relationship between stanniocalcin release in vivo and a hypocalcemic response and the first evidence concerning the functional turnover time of this hormone.

Anguilla↗

PubMed1991

Effect of increased intra-abdominal pressure on peristalsis in feline esophagus.

Our aim in this study was to determine the effect of variations in intrabolus pressure on esophageal peristalsis. In five cats, intrabolus pressure was altered by increasing intragastric pressure to 20-45 mmHg by use of a pressure cuff to compress the abdomen. In each cat, increases in intragastric pressure were associated with comparable increases in pressure of the esophageal bolus while the bolus was in the distal esophagus during esophageal peristalsis. Secondary peristalsis induced by a 5-ml injection of barium into the proximal esophagus was recorded by synchronized videofluoroscopy and esophageal manometry. Graded increases in intrabolus pressure caused an increased prevalence of ineffective, incomplete peristaltic sequences that did not completely clear barium from the esophagus. At intragastric pressures greater than 45 mmHg, 63% of the peristaltic sequences were incomplete. Increases in intrabolus pressure elicited by increased intragastric pressure also caused 1) slowing of the peristaltic wave in the distal esophagus, 2) increased pressure wave duration in the distal esophagus, 3) increased esophageal diameter, and 4) increased duration of lower esophageal sphincter opening. The incidence of retrograde bolus escape was inversely related to the difference between peristaltic wave amplitude and intrabolus pressure. A pressure difference of greater than 20 mmHg prevented retrograde barium escape at all esophageal levels, whereas a difference of less than 20 mmHg was generally associated with retrograde escape of barium in the distal esophagus. We conclude that an increase in intrabolus pressure causes an increase in esophageal distension that is transduced into alterations of esophageal peristalsis by either a myogenic or neural mechanism.

Abdomen↗