Simultaneous monitoring of gastric and oesophageal pH reveals limitations of conventional oesophageal pH monitoring in milk fed infants

BACKGROUND: Monitoring oesophageal pH conventionally detects "acid reflux" (pH less than 4). The pH of the gastric contents determines whether or not reflux can be detected. AIM: To monitor gastric and oesophageal pH simultaneously in order to determine the effect of milk feeds on gastric pH and how this would influence interpretation of the oesophageal pH record. METHODS: Milk fed infants for whom oesophageal pH monitoring was requested underwent simultaneous gastric and oesophageal pH monitoring using a dual channel pH probe. RESULTS: Twenty of 24 records were technically satisfactory. Mean reflux index was 1.0%, range 0.0-4.0%. Gastric pH was less than 4 for 24.5% (range 0.6-69.1%) of the total time. The average time the gastric pH was greater than 4 after feeds was 130 minutes (range 29-212 minutes). The corrected reflux index (limited to the time the gastric pH was less than 4) was 2.6% (range 0.0-11.0%). CONCLUSION: The pH of the gastric contents may be greater than 4 for prolonged intervals, during which oesophageal pH monitoring using current criteria cannot detect reflux nor correlate it with clinical events. A low reflux index may reflect prolonged buffering of gastric acidity rather than the absence of reflux.