Quantitation of the pharyngoesophageal sphincter in the dog.

The pressure and length of the pharyngoesophageal sphincter were studied in 5 healthy dogs that were awake and then immobilized with xylazine. During successive tests, a single side-hole catheter was mechanically withdrawn and rotated 90 degrees. Similar pressures were measured, regardless of the orientation of the catheter side hole. The mean pressure and length of the pharyngoesophageal sphincter of the awake dogs were 18 mm of Hg and 1.8 cm, respectively. After the dogs were immobilized with xylazine, the mean pressure and length were 8 mm of Hg and 1.7 cm, respectively. In 2 dogs immobilized with xylazine, there was no change in the maximum resting pharyngoesophageal sphincter pressure or length of the pressure zone after IV administration of edrophonium chloride, succinylcholine chloride, or thiamylal sodium. Seemingly, xylazine was not a suitable agent for immobilization of clinical patients for pharyngoesophageal manometry.