Non-invasive detection of gastro-oesophageal reflux using an ambulatory system

Acid, weakly acidic and non-acid gastro-oesophageal reflux: differences, prevalence and clinical relevance

In patients with gastro-oesophageal reflux disease (GORD), oesophageal symptoms and mucosal damage traditionally are related to acid-reflux episodes with pH lower than 4. Oesophageal or extra-oesophageal symptoms of GORD may also be associated with less acidic reflux (pH 4-7). New methodologies have evolved to complement pH monitoring for characterisation of less acidic gastro-oesophageal reflux. This review will focus on definition, detection, pathophysiology and symptom association of weakly acidic and non-acid reflux, in both adult and paediatric populations.

Gastro-oesophageal reflux monitoring: review and consensus report on detection and definitions of acid, non-acid, and gas reflux

To date, most concepts on the frequency of gastro-oesophageal reflux episodes and the efficiency of the antireflux barrier have been based on inferences derived from measurement of oesophageal pH. The development of intraluminal impedance monitoring has highlighted the fact that pH monitoring does not detect all gastro-oesophageal reflux events when little or no acid is present in the refluxate, even if special pH tracing analysis criteria are used. In November 2002, a workshop took place at which 11 specialists in the field of gastro-oesophageal reflux disease discussed and criticised all currently available techniques for measurement of reflux. Here, a summary of their conclusions and recommendations of how to achieve the best results from the various techniques now available for reflux measurement is presented.

Relationship between acid reflux episodes and gastroesophageal reflux symptoms is very inconstant

In this prospective study 244 consecutive patients presenting with typical and chronic signs of gastroesophageal reflux were included. Conventional 24-hr esophageal pH monitoring was carried out to establish the symptom association probability, the concordance index, and the symptom sensitivity index. The symptom association probability could be calculated in 110 patients (45%). Two groups were identified: group 1 had normal duration of esophageal acid exposure; subgroup la (nonsignificant symptom association probability) included 39 patients (35.5%) and subgroup lb (significant symptom association probability) included 24 patients (21.8%); group 2 had abnormal duration of esophageal acid exposure; subgroup 2a (nonsignificant symptom association probability) included 21 patients (19.1%) and subgroup 2b (significant symptom association probability) included 26 patients (23.6%). In all, 56.6% of the patients presented typical symptoms of reflux not directly determined by one or repeated acid reflux episodes. The correlation between symptom association probability and the symptom sensitivity index allows for more accurate determination of esophageal acid sensitivity (subgroups lb and 2b).

Composition of the postprandial refluxate in patients with gastroesophageal reflux disease

OBJECTIVE

It is not known whether the characteristics of the postprandial refluxate in patients with gastroesophageal reflux disease (GERD) differ from those observed in normal subjects. The aim of this study was to characterize the postprandial refluxate in adult patients with GERD using combined intraluminal electrical impedance and pH measurements.

METHODS

Postprandial gastroesophageal reflux was assessed in 16 patients with GERD and 15 controls. pH and intraluminal electrical impedance were used to identify acid and nonacid reflux of liquid, mixed (liquid + gas) or gas.

RESULTS

Transient lower esophageal sphincter relaxations (TLESRs) and reflux of gastric contents were equally frequent in both groups. However, patients with GERD had more acid reflux [8 (4.7-10.5)/h vs 3.5 (2.6-6)/h, p < 0.05], and normal subjects had more nonacid reflux [5 (4.3-6.7)/h is 3 (1-3.5)/h, p < 0.05]. Gas reflux was less frequent in GERD than in controls (51% vs 68%; p < 0.05). Pure liquid reflux, however, was more frequent (40% vs 26%, p < 0.05) and twice as likely to be acid in GERD. During TLESRs, liquid acid reflux was more frequent in GERD than in controls.

CONCLUSIONS

TLESRs and reflux of gastric contents are similarly frequent in patients with GERD and controls. However, patients with GERD have more acid reflux and less nonacid reflux. Differences in the air-liquid composition of the refluxate may contribute to the higher rate of acid reflux observed in these patients.

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 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.

Patterns of food and acid reflux in patients with low-grade oesophagitis--the role of an anti-reflux agent

BACKGROUND

Food and acid have been shown to be refluxed independently of each other in healthy volunteers, and anti-reflux agents decrease the reflux of both parameters. Until now this phenomenon had not been studied in patients with low-grade oesophagitis, who are the group most likely to use anti-reflux medication.

AIM

To assess patterns of gastro-oesophageal reflux of acid and food in 12 ambulant patients with endoscopically proven oesophagitis of between grades I and II, but who were otherwise healthy. Also to assess the effectiveness of a single dose of an alginate-containing anti-reflux agent in controlling food and acid reflux in this patient group.

METHODS

Oesophageal pH monitoring and external ambulatory gamma detection were used to study food and acid reflux. A pH electrode was positioned 5 cm above the cardia and the gamma detector was positioned externally over the pH electrode. The patients then received a technetium-99m labelled meal designed to provoke reflux. Thirty minutes later the patients were given a 20 ml dose of alginate (Liquid Gaviscon), or 20 ml of tap water. Incidence of reflux was monitored for approximately 4 h from the end of the meal. Allocation to treatment group was randomized, with patients receiving the alternative treatment on the second study day after approximately a 7-day washout period.

RESULTS

The mean percentage time oesophageal pH remained below 4 was 16.3 min for the control group and 5.4 min for the treatment group (P = 0.03). Food reflux was detected 23.7% of the time in the control group compared to 12% of the time in the treatment group (P = 0.02). The anti-reflux agent was also successful in decreasing the number of events, but the duration of the reflux events was not significantly different.

CONCLUSIONS

Patients with grades I and II oesophagitis reflux food and acid independently, and are predominantly either food refluxers or acid refluxers, but not both. Liquid alginate decreases the number of both food and acid reflux events, but does not change their duration.

An investigation of lower oesophageal redox potentials in gastro-oesophageal reflux patients and healthy volunteers

Oesophageal electrical properties are thought to be important in the development of gastro-esophageal reflux. This study simultaneously monitored the intraoesophageal pH and redox potentials in 18 patients with gastro-oesophageal reflux symptoms and 15 asymptomatic controls, for a 24 h period. The pH and redox electrodes were positioned 5 cm proximal to the lower oesophageal sphincter, the position of which had been determined by manometry. Since significantly different behaviour was observed during the day and night, the data were divided into periods of waking and sleeping. Data were analysed for acid reflux (pH < 4) and transients in the redox potential-time curve. Both patients and normal subjects showed negative redox transients which were more frequent and pronounced at night than during the day, and which were uncorrelated with acid reflux. The only parameter which was significantly different between normal and refluxing groups was the amount of nocturnal redox activity, which was lower in refluxing subjects than in normals. Some possible hypotheses for these observations, and the origin of the redox species, are discussed.

Effect of alginate and alginate-cimetidine combination therapy on stimulated postprandial gastro-oesophageal reflux

This randomized, single-blind cross-over study compared the effectiveness of a conventional alginate reflux barrier formulation (20 mL single dose of Liquid Gaviscon; sodium alginate, sodium bicarbonate, calcium carbonate) with a 20 mL single dose of an alginate-cimetidine combination formulation (Algitec Suspension; sodium alginate, cimetidine) in the suppression of food and acid reflux into the oesophagus after a test meal in 12 healthy volunteers. Subjects were fasted overnight before the study. A pH electrode and gamma detector were accurately positioned 5 cm above the cardia. The volunteers received a 99mTc-labelled meal designed to provoke reflux and then either remained untreated, or 30 min later were given either Algitec Suspension or Liquid Gaviscon. Reflux of both food and acid into the oesophagus was measured for 3 h. There was a seven day wash-out period between each treatment. Food reflux in the control group was 22,878 +/- 14,385 counts x 10(3) and this was significantly suppressed by both Liquid Gaviscon (174 +/- 128 (s.e.) counts x 10(3); P = 0.003); however, although the reduction of food reflux to 3812 +/- 2322 counts x 10(3) observed after Algitec treatment was considerable, this did not reach statistical significance (P > 0.05) due to the large intersubject variation. Liquid Gaviscon was significantly better at reducing food reflux than Algitec (P = 0.001). Gaviscon also significantly reduced acid reflux when compared with the control group (1.08 +/- 0.73 vs 5.87 +/- 3.27% recording time oesophageal pH < 4, respectively) (P = 0.03). The slight reduction in acid reflux after Algitec treatment (3.25 +/- 1.82% recording time oesophageal pH < 4) also did not reach statistical significance. The difference between Algitec and Gaviscon treatment was also not significant.

The effect of pectin on the gastric emptying rates and blood glucose levels after a test meal

This study was designed to evaluate the effect of pectin given in a palatable form on the gastric emptying rates of the solid and liquid phases of a test meal and to ascertain whether pectin affected blood glucose levels in ten healthy male and female volunteers. Gastric emptying was measured using dual isotope gamma scintigraphy. Allocation to the treatment group was double-blind and randomized. Sequential blood sampling was used to measure blood glucose levels. The times for the stomach to empty half the radiolabelled meal were similar after both pectin and placebo; however, a significant difference was seen between the AUC values of the meal between the two treatments. This can be attributed to the divergence of the emptying curves after the time point at which 50% of the meal had emptied, as pectin delayed the emptying of the last 20% of the meal. The initial phase of emptying for both pectin and placebo was significantly faster than the meal. No significant difference was found between blood glucose levels when either pectin or placebo was administered.