Figure 1.

Combined high-resolution manometry, pH and impedance monitoring in a patient with excessive belching and gastro-oesophageal reflux symptoms. The upper oesophageal sphincter is at the top of the figure and the lower oesophageal sphincter and stomach at the bottom. Contraction and aboral movement of the diaphragm creates an increased negative pressure in the oesophagus, with subsequent relaxation of the upper oesophageal sphincter. This results in an inflow of air into the oesophagus, seen as a progressive rise in impedance progressing down the oesophagus, followed by the immediate retrograde expulsion of air (air sucking). The supragastric belch is associated with lower oesophageal sphincter relaxation and reflux of acid into the oesophagus on the pH trace (the lowest white line) in the lower part of the figure.