Reflex Increase in the Gastroesophageal Junction High Pressure Zone Pressure During Sedated Endoscopy With Gastric Distension in Normal Volunteers

Abstract

Background: Gastric distension is a strong trigger for transient lower esophageal sphincter relaxation. In addition, it has been shown in prior unsedated studies that as the stomach is distended the pressure and length within the Gastroesophageal Junction High pressure Zone (GEJHPZ) decreases (Ayazi, Shahin MD et al, Annals of Surgery: July 2010 Volume 252 Issue 1 pp 57-62) Purpose: To evaluate the GEJHPZ pressure during gastric distension. Methods: Five normal volunteers (56.2 Yrs, 4F and 1M) were evaluated during upper endoscopy. A custom made manometry catheter with pressure ports spaced 3mm apart was attached to an Olympus ultrathin endoscope (GIF-N 180). Simultaneous manometry and endoscopy was recorded on an MMS swallowing work station. The endoscopy was performed under conscious sedation with Midazolam and Fentanyl. The endoscope was retroflexed to visualize the manometry catheter placed across the entire GEJHPZ. Baseline sphincter and gastric pressures were measured. Air was then insufflated into the stomach through the air channel of the endoscope with the air flow settings set at low (20ml/sec). Gastric and GEJHPZ pressures were measured continuously during air insufflation until a peak pressure was attained or the sphincter relaxed. All the pressures reported were relative to the gastric baseline pressure. To analyze the data, the start time was selected based on the lowest pressure at or just before the start of air insufflation, and the end point was selected where the pressure reached the peak within the GEJHPZ or just before sphincter relaxation. The duration to reach the peak pressure varied widely from subject to subject so the total duration was converted into 100% and then divided into 5 equal zones and an average pressure was calculated for each zone in the subjects. The peak and baseline pressures within the stomach and GEJHPZ were compared to each other using a paired student T test. The slope of the pressure change was determined. Results: The intragastric pressure increased from a mean of 6.19 mmHg to 12.34 mmHg at a slope of 1.09 (p=0.123). The GEJHPZ pressure increased from a mean 12.16 mmHg to 63.68 mmHg at a slope of 9.47 (p≤0.001). Conclusions: During sedated endoscopy, contrary to prior unsedated studies, gastric distension elicits a marked and significant reflex increase in the pressure and tone within the GEJHPZ as measured by intersphincteric pressure measurements using ultra-high resolution manometry. We measured the absolute change and the slope of the change of the pressures in both the stomach and the GEJHPZ during distension of the stomach with air. We believe that this gastric/GEJHPZ reflex is an important mechanism that protects the esophagus from reflux of gastric contents during increases in intragastric pressure.