RESUMO
Ambulatory pH monitoring detects abnormal levels of acid reflux in the oesophagus and can be used to correlate patients' symptoms with oesophageal acid exposure. Catheter-based pH testing has several limitations, including issues of sensitivity, specificity, tolerability and the inability to record non-acid reflux events. In an effort to improve upon these drawbacks, several devices have been introduced, including the Bilitec system for measuring duodenogastro-oesophageal reflux; intraluminal impedance monitoring, which detects the distribution, composition and clearing of both acid and non-acid oesophageal reflux; and a wireless pH monitoring device, the Bravo capsule. Initial investigations using the Bilitec system demonstrated that duodenogastro-oesophageal reflux tracked very closely with acid reflux and decreased with proton-pump inhibitor (PPI) therapy, casting doubt on the clinical utility of Bilitec monitoring. Recent evidence revealed a possible role for duodenogastro-oesophageal reflux in a subset of patients who continue to report reflux symptoms in the setting of normalized oesophageal acid exposure on high-dose PPI therapy. When combined with pH monitoring, impedance monitoring enhances the detection and characterization of gastro-oesophageal reflux and may have a role in the evaluation of certain specific gastro-oesophageal reflux disease (GERD) symptoms that persist despite acid suppression therapy. The utility of the Bravo wireless technology for GERD diagnosis has been validated in several studies, with improvements over catheter-based pH monitoring in tolerability, accuracy and sensitivity, as well as the ability to record periods both off and on PPI therapy in a single study. All three diagnostic modalities have advanced the understanding of GERD pathogenesis, but their impact on the clinical management of GERD is still the focus of active investigation.