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% P = 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.

© 2011 Blackwell Publishing Ltd.