The location of the upper oesophageal sphincter and its behaviour during bolus propagation--a simultaneous cineradiographic and manometric investigation.

By means of simultaneous cineradiographic and manometric examinations using closely positioned microtransducers the maximal pressure of the upper oesophageal sphincter was found at a level 20 mm below the plane of the vocal folds and 6 mm above the level of the cricoid arch. The sum of these 2 distances is in accordance with the distance between the vocal fold level and the lower border of the cricoid arch given in the literature. This implies that the high pressure zone of the upper oesophageal sphincter corresponds to the pars fundiformis of the cricopharyngeus muscle. The lower part of the inferior pharyngeal constrictor and the upper circular muscle fibres of the oesophagus contribute to the sphincter. When the bolus approached the sphincter, the pressure decreased and during bolus passage the pressure was below or well below half of the resting pressure. The pressure profile disclosed no signs of muscular dyscoordination or discontinuity of the upper oesophageal sphincter.