Patterns of gas and liquid reflux during transient loweroesophageal sphincter relaxation: a study using intraluminal electricalimpedance

Background—Belching has beenproposed as a major mechanism underlying acid gastro-oesophageal refluxin normal subjects. However, the presence of oesophageal gas hasnot been measured directly but only inferred from manometry.
Aims—To investigate, usingintraluminal electrical impedance, the patterns of gas and liquidreflux during transient lower oesophageal sphincter (LOS) relaxations,the main mechanism of acid reflux in normal subjects.
Methods—Impedance changesassociated with the passage of gas were studied in vitro, and in vivoin cats. Oesophageal manometry, pH, and intraluminal electricalimpedance measurements were performed in 11 normal subjects after a meal.
Results—Gas reflux caused asudden increase in impedance that propagated rapidly to the proximaloesophagus whereas liquid reflux induced a retrogressively propagatedfall in impedance. Impedance showed gas or liquid reflux during most(102/141) transient LOS relaxations. When acid reflux occurred,impedance showed evidence of intraoesophageal retrograde flow of liquidin the majority (78%) of events. Evidence of gas retroflow was foundin almost half (47%) of acid reflux episodes. When present together,however, liquid preceded gas on 44% of occasions. Overall, gas refluxoccurred as the initial event in only 25% of acid reflux episodes.
Conclusions—These findings suggestthat in upright normal subjects, although belching can precipitate acidreflux, most acid reflux occurs as a primary event.

Keywords:belching; gastro-oesophageal reflux disease; oesophageal manometry; intraluminal electrical impedance; loweroesophageal sphincter