Oesophageal pH monitoring in infants: Elimination of gastric buffering does not modify reflux index

Background: Oesophageal pH monitoring is considered to be the gold standard investigation in the diagnosis of gastro-oesophageal reflux disease. Resul ts of pH monitoring in regurgitating infants, however, may be within normal ranges. Therefore it was hypothesized that prolonged buffering of gastric acidity caused by milk-feeding may falsely normalize the pH data. Therefore , it may be relevant to omit the periods of gastric acid buffering in the a nalysis of the oesophageal pH monitoring data. Methods: Combined gastric and oesophageal pH monitoring (Digitrapper Mark I II, two-channel antimony electrode, Synectics) was performed in 90 consecut ive infants, 0.5-10 months old, who were referred to the unit by our-door p aediatricians for pH measurement. The data were analysed in three different ways. The reflux index (RI), or the percentage time that the pH in the oes ophagus was < 4.0, was calculated in three different ways: (i) the total du ration of the investigation; (ii) excluding 90-min postprandial periods, st arting from the beginning of a feeding; and (iii) excluding all periods wit h a gastric pH > 4.0, which are the periods of gastric buffering with a the oretical impossibility of recording an oesophageal pH < 4.0. Results: The mean duration of the pHmetries was 19.20+/-2.01 h (A; mean al SD), with a RI of 5.38 +/- 5.39% (B; median 3.45%). If the 90-min postprand ial periods were not considered, the mean duration decreased to 12.21 +/- 2 .41 h (C; P(A vs C) < 0.001), with an oesophageal RI of 6.82 +/- 6.57% (D; median: 4.65; P(B vs D) = NS; r (B vs D) = 0.97). If all periods with a gas tric pH > 4.0 were elminated, the duration available for analysis of the da ta with a gastric pH < 4.0 was 12.53 +/- 4.00 h (E; P(A vs E) < 0.001; P(C vs E) = NS), with an oesophageal RT of 7.06+/-7.52% (F; median: 4.50; P(B v s D vs F) = NS; r(B vs F), (D vs F) = 0.96). Conclusion: Overall the data do not support a benefit from including period s of gastric buffering in the routine analysis of oesophageal pH monitoring data. Therefore standard oesophageal pH monitoring should be with a single electrode and should not include periods of gastric buffering. (C) 2000 Bl ackwell Science Asia Pty Ltd.