Since its introduction in 1974,¹ ambulatory oesophageal pH monitoring has secured a valuable but complementary role in the diagnosis of gastro-oesophageal reflux disease. Monitoring of oesophageal pH allows not only the detection of excessive levels of acid exposure but also, and more importantly, assessment of the relationship between acid reflux and symptoms. It is especially useful for clarification of the diagnosis in patients with typical or atypical reflux symptoms who do not response to empirical therapy with a proton pump inhibitor, and for assessment of the level of acid suppression in patients with refractory symptoms or oesophagitis despite appropriate antisecretory therapy.^2,3

The traditional method of pH monitoring uses a pH electrode mounted on a catheter that is passed transnasally into the oesophagus and positioned 5 cm above the manometrically defined upper border of the lower oesophageal sphincter. The catheter is connected to a portable data logger thereby allowing ambulatory recordings to be made. Ideally, the circumstances under which the pH recordings are made should reflect, as best as possible, the usual living conditions and physical activities normally undertaken by the patient. However, because the catheter is conspicuous and uncomfortable, most patients restrict their activities and dietary intake,^4,5 which could potentially lead to false negative results. In addition, because the electrode is not fixed to the oesophageal wall but rather to the nose, it can become displaced, or transiently “migrate” into the stomach in patients with large mobile hiatus hernias, thereby altering the amount of reflux that is recorded⁶ and potentially leading to erroneous recordings.⁷

Recently, a new pH monitoring system has been developed that overcomes these limitations …