A two-layered mechanical model of the rat esophagus. Experiment and theory

BACKGROUND: The function of esophagus is to move food by peristaltic motion which is the result of the interaction of the tissue forces in the esophageal wall and the hydrodynamic forces in the food bolus. The structure of the esophagus is layered. In this paper, the esophagus is treated as a two-layered structure consisting of an inner collagen-rich submucosa layer and an outer muscle layer. We developed a model and experimental setup for determination of elastic moduli in the two layers in circumferential direction and related the measured elastic modulus of the intact esophagus to the elastic modulus computed from the elastic moduli of the two layers. METHODS: Inflation experiments were done at in vivo length and pressure-diameters relations were recorded for the rat esophagus. Furthermore, the zero-stress state was taken into consideration. RESULTS: The radius and the strain increased as function of pressure in the intact as well as in the individual layers of the esophagus. At pressures higher than 1.5 cmH(2)O the muscle layer had a larger radius and strain than the mucosa-submucosa layer. The strain for the intact esophagus and for the muscle layer was negative at low pressures indicating the presence of residual strains in the tissue. The stress-strain curve for the submucosa-mucosa layer was shifted to the left of the curves for the muscle layer and for the intact esophagus at strains higher than 0.3. The tangent modulus was highest in the submucosa-mucosa layer, indicating that the submucosa-mucosa has the highest stiffness. A good agreement was found between the measured elastic modulus of the intact esophagus and the elastic modulus computed from the elastic moduli of the two separated layers

Peristalsis in an interposed colonic segment immediately following total oesophagogastrectomy

BackgroundThe motility pattern of colon used for oesophageal replacement in an oesophagogastrectomy is thought to be altered following interposition. Whether this is the result of adaptation or the removal of motor control mechanisms is unknown. Motility patterns of the interposed colon during the immediate postoperative period have not been previously studied.MethodsA patient who had an oesophageal adenocarcinoma and an unhealed gastric ulcer, underwent total gastrectomy and oesophagectomy. A colonic segment oriented isoperistaltically was used for oesophageal replacement. During the surgery, a customized 10 channel motility catheter was introduced transnasally into the colonic segment, and 24 h after surgery measurement of motor activity was undertaken using a perfused manometric system.ResultsPeristaltic contractions were observed with a mean contraction amplitude of 39.6 mmHg in the proximal channel, 90.3 mmHg in the distal channel and a mean propagation velocity of 0.51 cm/s.ConclusionsPeristaltic colonic contractions continue to occur in the early postoperative period in the colonic segment used to replace the oesophagus. In view of this, colon replacing the oesophagus should always be arranged in an isoperistaltic fashion.Myers, J. C.; Mathew, G.; Watson, D. I.; Jamieson, G. G

A comparison of micromanometric and standard manometric techniques for recording of oesophageal motility

Perfused micromanometric assemblies with an outer diameter of 2 mm or less have been developed for use in premature infants and small laboratory animals. Such assemblies offer advantages with regard to subject comfort and low perfusion rates that make them attractive for use in adults. The aim of this study was to investigate the recording fidelity of micromanometric assemblies in the measurement of oesophageal peristalsis in adults. Two micromanometric assemblies with an outer diameter of 1.8-2.0 mm and a length suitable for use in adults (165 cm), and containing micromanometric lumina of 0.28-0.35 mm i.d. and a standard lumen of 0.6-0.75 mm i.d. were evaluated. Each assembly was tested by measurement of pressure rise rate in response to sudden occlusion, and in vivo during oesophageal peristalsis by simultaneous comparison with an intraluminal strain gauge. At perfusion rates of 0.01-0.15 mL min-1 microlumina achieved pressure rise rates of 21-430 mmHg sec-1 that were comparable to 37-390 mmHg sec-1 for the standard lumina perfused at 0.15-0.6 mL min-1. During oesophageal peristalsis, micromanometric lumina recorded the occurrence and timing of all pressure waves accurately when compared with standard lumina and the microtransducer. However, microlumina under-recorded pressure wave amplitude to varying degrees dependent upon perfusion rate although the performance of microlumina could be improved to that of the standard lumen by shortening their length to 70 cm. Micromanometric assemblies are suitable for recording oesophageal peristalsis in adults although there is some impairment of absolute manometric fidelity. Fidelity can be improved by minimizing total assembly length