Esophageal pH monitoring.
In the 25 years since it was first described, prolonged esophageal pH monitoring has gained increasing acceptance and popularity as a diagnostic and research technique in GER disease. Some recent developments that have contributed to its attraction include compact portable recorders, computerized analysis, short monitoring periods, the good discriminant value of the simple measurement of percent monitoring time that pH is less than 4, and the symptom index, allowing correlation of symptoms with reflux events. Nevertheless, there remain areas of uncertainty with regard to reproducibility and the conditions of monitoring, in particular whether strict dietary control and controlled activity and posture are necessary. There is no universally accepted normal range of values, but it is now apparent that normal and abnormal GER are not appropriately differentiated by simply defining the upper limit of normal using a formula of the mean plus two standard deviations, so other statistical techniques have emerged. Indications for the technique include atypical symptoms, particularly noncardiac chest pain, respiratory symptoms, and, in young children, apneic attacks and recurrent vomiting associated with failure to thrive. The technique is having an impact on the assessment prior to, during, and after medical and surgical therapy for GER, as well as in helping to unravel the complexities of the pathogenesis of esophagitis.