Perception of gastric distension. Influence of mode of distension on perception thresholds and gastric compliance

Gastric distension has been used to evaluate gastric sensory function in humans, but the methodology is poorly validated and studies in vivo comparing different distension protocols are lacking. We aimed to compare the influence of the mode of gastric distension on sensation and gastric compliance utilizing a barostat device. In seven healthy volunteers, we positioned a barostat bag in the proximal stomach and tested in random order (in triplicate) four different distension protocols: (1) standard ramp distension with 4 mm Hg pressure step increments of 20 sec duration; (2) slow ramp distension with 2 mm Hg pressure increments of 40 sec duration; (3) random distension using a pressure ramp consisting of 2 mm Hg increments of 40 sec duration with randomly interposed pressure steps 50% below the preceding pressure step; and (4) rapid random distension with 4 mm Hg pressure increments of 10 sec duration with randomly interposed pressure steps 50% below the preceding pressure step. The distension procedures yielded mean airflow rates during the different distension protocols between 2.4 ml/sec for standard ramp and 18.4 ml/sec for rapid random distension. First perception and maximal tolerable pressure were 10.9 +/- 1.1 mm Hg and 19.6 +/- 1.5 mm Hg, respectively. First perception and maximal tolerable pressures were significantly correlated (r = 0.93, P < 0.005). The gastric pressure at occurrence of perception and the maximal tolerated pressure were not significantly different for the different distension protocols but gastric compliance was significantly reduced during rapid ramp distension (P < 0.01 vs slow ramp and P < 0.05 vs random distension) but not during standard ramp distension. We conclude that gastric sensory pressure thresholds as assessed by isobaric distension are not influenced by the mode of distension. The high correlation of pressure thresholds at first perception and maximal tolerated distension suggest a single population of gastric mechanoreceptors that mediate first sensation at low intensity stimulation and pain at intense stimulation.