Which of the following statements about the lower esophageal sphincter (LES) mechanism, or high-pressure zone (HPZ), is true?

B. In assessing esophageal manometric data, mean HPZ pressure less than 6 mm. Hg or overall length less than 2 cm. is more likely to be associated with incompetence of the LES and gastroesophageal reflux.

DISCUSSION: The LES is not an anatomic muscular sphincter like the anus or pylorus, but rather, is a functional sphincter that serves as a barrier against abnormal regurgitation of gastric contents into the esophagus and is more appropriately termed the distal esophageal HPZ. While, in general, no HPZ value absolutely indicates either competence or incompetence of the LES mechanism, patients with a mean HPZ pressure less than 6 mm. Hg or a sphincter length less than 2 cm. are likely to have an incompetent LES and gastroesophageal reflux. Esophageal manometry defines the amplitude and length of the distal HPZ and the character of esophageal peristalsis. It does not determine whether or not the LES is competent. The Bernstein test identifies the patient with an acid-sensitive esophagus but does not indicate whether or not the patient has gastroesophageal reflux or esophagitis. Reflex distal HPZ relaxation occurs within 1.5 to 2.5 seconds after a swallow is initiated and lasts 4 to 6 seconds. Twenty-four–hour distal esophageal pH monitoring is achieved by means of an intraesophageal pH electrode positioned 5 cm. proximal to the HPZ, as determined by prior manometric evaluation.