Modulation of Feline Esophageal Contractions by Bolus Volume and Outflow Obstruction

We studied the effect of bolus volume and esophageal obstruction on esophageal peristalsis by using synchronized video-fluoroscopic and manometric techniques in cats. A specially designed pressure cuff was surgically implanted around the distal esophagus to control the degrees of outflow obstruction. Secondary esophageal peristalsis was evoked by injecting bolus volumes of 3, 6, and 9 ml at cuff pressures of 0, 20, 40, and 60 mmHg. Increases in outflow obstruction reduced the velocity of peristalsis. The amplitude of esophageal contraction increased with increasing outflow obstruction at low bolus volumes but decreased with larger bolus volumes and larger outflow obstruction. In the absence of outflow obstruction, each esophageal contraction traversed the entire esophagus distal to its site of origin, but in the presence of outflow obstruction contractions only traversed part of the esophagus. The incidence and site of failure of propagation was directly related to cuff pressure and bolus volume. The relationship between the onset of manometric pressure complex at a given site in the esophagus to the passage of the bolus from that esophageal site was markedly affected by outflow obstruction. We conclude that esophageal peristalsis can be modulated by the bolus volume and outflow obstruction.