Purpose: The gastroesophageal junction (GEJ) antireflux barrier consists of end-expiratory lower esophageal sphincter (LES) tone with superimposed phasic respiratory pressure changes representing the crural diaphragm. Esophageal manometry is usually performed with water swallows with the subject supine, an unnatural position for eating meals. The aim of this study was to establish normal values for high resolution manometry for swallowing water and viscous boluses in the supine and upright positions.
Methods: 15 normal volunteers (ages 19 to 45 years; 8 males, 7 females) underwent esophageal manometry using a high resolution manometry catheter with 36 solid state circumferential pressure sensors spaced 1 cm apart (Sierra Scientific Instruments). The catheter was placed transnasally with sensors spanning the pharynx, esophagus, LES, and proximal stomach. Each subject performed twelve 5 ml water swallows in the supine position, six 5 ml water swallows upright and six 5 ml viscous swallows (Jello) upright. Results are expressed as mean ± SEM.
Results: The esophageal length was 25.5 ± 1.4 cm; the GEJ high pressure zone was 4.2 ± 0.2 cm. There were no double high pressure zones suggestive of hiatal hernia. The end-expiratory basal LES pressure was lower in the upright position (3.4 ± 0.9 mmHg) than supine (16.9 ± 1.8 mm Hg; p < 0.01). The mid-respiratory LES pressure was lower upright (8.8 ± 1.1 mmHg) than supine (27.1 ± 1.5 mm Hg; p < 0.01). The crural diaphragm component, represented by the difference of mid-respiratory and end-expiratory pressures, was also less upright (8.6 ± 0.9) than supine (10.8 ± 1.3; p= 0.056). Swallow-induced esophageal contractions were reduced in amplitude upright (62 ± 9 mm Hg 5 cm above LES) compared to supine (74 ± 7 mm Hg; p= 0.036). Swallows using jello in the upright position had an increase in esophageal contraction pressures (73 ± 10 mmHg) compared to water swallows upright (62 ± 9 mm Hg; p= 0.051) without change in peristaltic velocity.
Conclusions: This study demonstrates positional pressure changes in the GEJ high pressure zone of both the intrinsic LES and extrinsic crural components. The reduction of the GEJ high pressure zone in the upright position may be due to the additional presence of gravitational forces preventing reflux as well as anatomic changes. The decrease in the antireflux barrier upright might explain, in part, postprandial gastroesophageal reflux that occurs in normal subjects.