24-hour oesophageal two-level pH monitoring in healthy children and adolescents.

Two-level pH recording in the oesophagus was performed for 24 h in 28 healthy schoolchildren between 9.3 and 17.3 years of age, to obtain reference values for reflux studies. The pH probes were placed 5 and 15 cm above the lower oesophageal sphincter by means of the manometric technique. A standardized acid-free diet was given on the day of recording. A drop in pH to 4.0 or below was regarded as reflux. The normal upper limit of total reflux time was 1.0% at the lower oesophageal level. Mean reflux time was about three times shorter at the upper level than at the lower, which indicates the importance of exact positioning of the pH probe.