Technique for prolonged, minimally invasive monitoring of intragastric pH in ponies.

This research study investigated a method for long-term, minimally invasive monitoring of stomach acidity levels in ponies.

Research Methodology

• The researchers conducted their initial experiments on cadaver pony stomachs to determine the efficiency of different types of electrodes in measuring pH levels.
• It was found that non-weighted electrodes gave high pH readings when they came in contact with the stomach lining, while weighted electrodes were much less affected by mucosal contact. Thus, weighted electrodes were selected for the subsequent real-life, or in vivo, trials.

In Vivo Trials

• In living ponies, a high correlation was found between pH readings recorded by weighted electrodes, regardless of whether a wire guard was used to prevent contact with the stomach lining. These readings correlated well with those from simultaneous gastric fluid aspirates, suggesting that the electrodes were accurately measuring pH levels.
• The researchers noticed that plain electrodes recorded more highly variable pH readings – this meant these readings changed more over time compared to guarded electrodes.
• In the lab, trials with equine (horse) stomach fluid showed that this variability was likely due to the plain electrode being more responsive.

Observations and Analysis

• The researchers observed periods of nearly neutral pH frequently in the ponies. They found that high pH levels correlated with the presence of yellow-green, neutral fluid in the pony’s stomach. However, the concentration of bile acids in the stomach did not correlate with pH or the color of the fluid.
• The researchers suggest that these neutral pH periods could be due to the influx of saliva into the stomach, gastric fluid refluxing back into the stomach from the small intestine, or changes in the secretion of stomach acid.
• Administration of the drug pentagastrin, which stimulates acid secretion in the stomach, was found to reduce stomach pH levels, although neutral pH episodes still occurred.

Conclusion

• The researchers concluded that intragastric pH monitoring can be a useful technique. For instance, it was often able to identify episodes of increased pH, which might indicate reflux of gastric fluid from the small intestine back into the stomach.
• However, they found that care was required in how the pH data was summarized and presented.