Twenty-four-hour Ambulatory Oesophageal PH Monitoring: Experience in The Netherlands

Twenty-four-hour ambulatory oesophageal pH monitoring has become a major diagnostic method for the evaluation of gastro-oesophageal reflux disease. Essential requirements for registration and reproduction of the pH are reliable pH electrodes, well-performed calibration and optimal reproduction and analysis of the signal. The most commonly used pH probes in The Netherlands are not-combined monocrystalline antimony electrodes (Synectics Ltd, Sweden) and combined glass electrodes (Ingold and Radiometer). For diagnostic intra-oesophageal pH measurements both types are suitable; for research purposes, especially intragastric, glass electrodes are preferable. In The Netherlands several types of solid-state recorders are commercially available: all fulfill the conditions necessary to produce reliable registrations. In the present study, available measuring systems in The Netherlands and current practices associated with ambulatory pH monitoring were evaluated. Inquiry among the Dutch pH registration centres showed that more than half were using Synectics electrodes and equipment. Positioning of the pH probe was based on manometry (25%), fluoroscopy (22%) or endoscopy (20%). In the initial phase there were many problems, especially related to ignorance of the complicated registration procedure. For ambulatory pH measurements we recommend a simple datalogger with a sufficient memory capacity and direct interface with a PC, a combined glass electrode positioned 5 cm above the manometrically determined lower oesophageal sphincter. For clinical interpretation of the results the percentage of time with pH below 4 is probably the most reliable parameter for the detection of pathological gastrooesophageal reflux.