Pressure Characteristics of the Esophagus and Its Sphincters in Dogs

Abstract

The pressure in the esophagus and its sphincters in seven well-trained, intact, healthy dogs was studied using three small water-filled polyethylene tubes attached to pressure transducers. To obtain resting pressures these tubes were withdrawn at intervals of 0.5–2.0 cm through the gastroesophageal junction, the esophagus and the pharyngoesophageal junction. Swallowing was induced by injection of water into the mouth or pharynx of the animals, and responses were recorded from selected sites. At rest, bands of elevated pressure about 2 cm wide were detected at the pharyngoesophageal and gastroesophageal junctions. The mean maximal pressures in the two zones were 20 and 6.9 cm of water, respectively. Pressure in the esophagus at rest was less than that in the gastric fundus. When swallowing began, the elevated pressure in the junctional zones decreased promptly, rose to high values as the peristaltic wave of deglutition swept into them, and then declined to resting levels. A peristaltic wave of high pressure swept through the esophagus with each swallow. These findings indicate that the junctional zones act as sphincters. Their behavior is identical to that in healthy human beings. The pressure pattern in the esophagus itself with swallowing is also the same in the two species, but in the dog the peristaltic wave moves faster and the rise of pressure is briefer. These differences may reflect the fact that the muscle of the dog's esophagus is entirely skeletal.