| Research Abstract |
The upper esophageal sphincter prevents reflux into the pharynx. If it function improperly, aspiration pneumonia can result. We studied the functioning of the sphincter in unaanesthetized dogs after denervation under anesthesia of the recurrent laryngeal nerves. the pressure of the sphincter at rest was measured by manometry with a transduoer that measured pressurre around the tip of a catheter. Then the pressurre in response to inflation of a balloon to the diameter of 1.5,2.0 and 2.5cm and at 5 and 10cm aboral to the sphincter was measured. Next, the pressure during perfusion of 0.1 NHCl or NaOH 10cm aboral to the sphincter was measured. These studies were done first in 10 dogs that had undergone only gastrostomy for measurements (controls). Measurements were repeated after the left recurrent laryngeal nerve in the control was cut (L group), after the right recurrent laryngeal nerve in the L group was cut (B group), and after transsection of the esophagus 7cm aboral to the sphincter in the B group (Tgroup). The differences in the pressure at rest were not significant. In each group, balloon inflation to any diameter tested and at either position made the pressure rise above that at rest. This pressure in the L,B,and T groups, however, was significantly lower than in the controls. When the balloon was inflated to 2.5cm when it was 10cm aboral to the sphincter, the pressure in the T group was significantly lower than in the Bgroup. When HCl or NaOH were perfused, the pressure increased gradually in the controls, but not in the other groups. In conclusion, although recurrent laryngeal nerves did not affect the function of the sphincter at rest, they were the afferent routes of the contration by the sphincter as a reflex following distension or chemical stimulation of the esophagus. The intramural nerve network of the cervical esophagus may be another reflex route of contraction of the upper esophageal sphincter.
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