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

Abstract

Background: Belching has been proposed as a major mechanism underlying acid gastro-oesophageal reflux in normal subjects. However, the presence of oesophageal 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 in vitro, and in vivo in cats. Oesophageal manometry, pH, and intraluminal electrical impedance measurements were performed in 11 normal subjects after a meal.

Results: Gas reflux caused a sudden increase in impedance that propagated rapidly to the proximal oesophagus whereas liquid reflux induced a retrogressively propagated fall 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 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 initial event in only 25% of acid reflux episodes.

Conclusions: These findings suggest that in upright normal subjects, although belching can precipitate acid reflux, most acid reflux occurs as a primary event.

Figure 1

Schematic representation of recording assemblies in the normal subjects. The hatched areas on the impedance assembly indicate 2 cm recording segments between pairs of electrodes.

Figure 2

Tracing of concurrent manometry, pH, and intraluminal impedance. Primary peristalsis (sw) is associated with a sequential drop in impedance that propagates in an antegrade fashion. A transient LOS relaxation (TLOSR) occurs after the first primary peristaltic sequence and is associated with liquid acid reflux as evidenced by a fall in pH (indicated by the vertical dashed line), and a retrogressively propagated drop in impedance (arrows) that precedes the pH drop.

Figure 3

Radiographic appearance (left) and oesophageal impedance changes (right) associated with gas reflux in the cat. The x ray shows an oesophageal common cavity with gas evident in both the stomach (white arrow) and oesophagus (black arrow). This reflux episode was associated with an abrupt, almost simultaneous increase in impedance at all measuring segments.

Figure 4

Impedance changes associated with the upward movement of a gas bubble in a column of water.

Figure 5

Radiographic appearance (left) and oesophageal impedance changes (right) associated with liquid reflux in a cat. The x ray shows liquid in both the stomach (white arrow) and oesophagus (black arrow). The gastro-oesophageal reflux episode was associated with a retrogressively propagated drop in impedance (arrows).

Figure 6

Patterns of reflux during transient LOS relaxations based on pH and manometric criteria. The pie chart shows the proportion of different impedance patterns observed during transient LOS relaxations. TLOSR, transient LOS relaxation. cc, common cavity.

Figure 7

Tracing of concurrent manometry, pH, and intraluminal impedance. A transient lower oesophageal sphincter relaxation (TLOSR) is associated with a common cavity and acid reflux as evidenced by a pH drop. The impedance tracing shows an initial drop (open arrows) consistent with liquid reflux followed by a large, abrupt, and almost simultaneous increase (closed arrows), indicative of gas reflux.

Figure 8

Tracing of concurrent manometry, pH, and intraluminal impedance during an uneventful (absence of common cavity and pH change) transient lower oesophageal sphincter relaxation (TLOSR). The horizontal dashed line indicates the level of intragastric pressure. The TLOSR is associated with a retrogressively propagated drop in impedance (arrows) caused by non-acidic liquid reflux.