Gastric Compliance, Sensation, and the Relaxation Response to a Nitric Oxide Donor in Health and Reflux Oesophagitis

Abstract

Background/Aims: The gastric fundus affects afferent control of lower oesophageal sphincter function. Nitric oxide is an important relaxant of the fundus. We postulated that gastric distensibility, compliance and nitric oxide sensitivity may be altered in patients with gastro-oesophageal reflux disease (GERD). Methods: 9 patients with erosive oesophagitis (6 males; median age 55 years) and 16 healthy controls (9 males; median age 36 years) were studied fasting with a gastric barostat. Minimal distending pressure (MDP) and gastric compliance (Δv/Δp) were determined by increasing intrabag pressure in 2-mm Hg increments. The pressures required to produce initial sensation and maximum tolerated sensation were recorded. With the intrabag pressure set at MDP +2 mm Hg, 500 μg sublingual glyceryl trinitrate was administered and the percentage change in intrabag volume from initial volume recorded. Results: The MDP was significantly greater in patients than controls (7.5 vs. 6.7 mm Hg median; p = 0.02). Gastric compliance was similar in both groups (57.8 vs. 67.2 ml/mm Hg; p = 0.4). There was no difference between groups in the pressure at first intragastric sensation (11.2 vs. 10.3 mm Hg above MDP; p = 0.5) or in the maximal tolerated pressure (15.8 vs. 14.3 mm Hg above MDP; p = 0.2). The proportional change in gastric volume from baseline in response to glyceryl trinitrate was smaller in patients than controls (66 (3–200) vs. 120 (26–1,053)%; p = 0.02). Conclusions: Gastric MDP may be altered in GERD, but gastric compliance and sensitivity to distension are normal. Major gastric relaxation occurs in response to a nitric oxide donor, but this appears to be diminished in patients with GERD. Upper gut nitrinergic mechanisms may be altered in oesophageal reflux disease.