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Aliment Pharmacol Ther 2011; 34: 568–575

Summary

Background  Exclusion of the meal during ambulatory pH monitoring presumes that a meal completely buffers gastric acid and reflux of acidic food content cannot be distinguished from gastric acid. However, the ability of a meal to completely buffer gastric acid remains unclear.

Aim  To determine the effect of a weakly acid meal on gastric buffering and oesophageal acid exposure.

Methods  Patients undergoing multichannel intraluminal impedance pH studies were given a standard weakly acidic meal (pH = 5.9). Gastric and oesophageal pH was measured during the meal and in 15 min intervals for 2 h postprandially.

Results  The study included 30 patients, with pathological acid reflux detected in 18 patients. Complete gastric buffering occurred in seven patients (23%) and was lost in all patients within 75 min of the meal. Oesophageal acid was detected in 33% of patients within 30 min of the meal and 81% of patients during the 2 h postprandial period. Postprandial oesophageal acid exposure was greater in patients with pathological acid reflux (9 ± 2.7% vs. 1.7 ± 0.8%= 0.05) with a trend towards more incomplete gastric acid buffering and significant differences when measuring weak acid reflux (pH 4–5). Acid reflux rarely occurred in the absence of gastric acid, with gastric acid present in 74 of 79 (94%) fifteen minute postprandial intervals with acid reflux.

Conclusions  The ability of a meal to buffer gastric acid is poor. Early postprandial oesophageal acid reflux occurs in a substantial proportion of patients. Addition of a weakly acidic or pH neutral meal to ambulatory pH monitoring may unmask early postprandial acid reflux and provide data on gastric acid buffering.