Patterns of gas and liquid reflux during transient lower oesophageal sphincter relaxation: a study using intraluminal electrical impedance

Background-Belching has been proposed as a major mechanism underlying acid gastro-oesophageal reflux in normal subjects. However, the presence of oeso phageal gas has not been measured directly but only inferred from manometry . Aims-To investigate, using intraluminal electrical impedance, the patterns of gas and liquid reflux during transient lower oesophageal sphincter (LOS) relaxations, the main mechanism of acid reflux in normal subjects. Methods-Impedance changes associated with the passage of gas were studied i n vitro, and in vivo in cats. Oesophageal manometry, pH, and intraluminal e lectrical impedance measurements were performed in 11 normal subjects after a meal. Results-Gas reflux caused a sudden increase in impedance that propagated ra pidly to the proximal oesophagus whereas liquid reflux induced a retrogress ively propagated fall in impedance. Impedance showed gas or liquid reflux d uring most (102/141) transient LOS relaxations. When acid reflux occurred, impedance showed evidence of intraoesophageal retrograde flow of liquid in the majority (78%) of events. Evidence of gas retroflow was found in almost half (47%) of acid reflux episodes. When present together, however, liquid preceded gas on 44% of occasions. Overall, gas reflux occurred as the init ial event in only 25% of acid reflux episodes. Conclusions-These findings suggest that in upright normal subjects, althoug h belching can precipitate acid reflux, most acid reflux occurs as a primar y event.