Determinants of lower esophageal sphincter relaxation induced by esophageal balloon distension in humans.

The determinants of the lower esophageal sphincter relaxation response to esophageal distension have not previously been systematically examined in humans. In this study, 14 healthy subjects were tested using a manometry catheter with a sleeve device and three balloons spaced 5 cm apart. Subjects had up to five distensions with each balloon at four different diameters and two different durations of inflation. The results indicated that 1,170 separate distensions were available for analysis. Sphincter relaxation occurred more frequently (P < 0.005) with larger balloon diameters, yet occurred in only 84% of inflations at the largest diameter. Sphincter relaxation was more often observed with the proximal balloon (P < 0.005) during longer distensions (P < 0.05) and when esophageal contractions occurred above the balloon (P < 0.005). Once sphincter relaxation occurred, its magnitude was essentially independent of balloon site and diameter, distension duration, and the presence of proximal contractions. In conclusion, even large balloon distensions do not uniformly produce or maintain lower esophageal sphincter relaxation. Sphincter relaxation is more likely with proximal esophageal distension. The association of sphincter relaxation with vagally mediated proximal contractions suggests vagal modulation of this response.