Normative values in esophageal high-resolution manometry

Esophageal high-resolution manometry (HRM) has rapidly gained much popularity worldwide. The Chicago Classification for esophageal motility disorders is based on a set of normative values for key metrics that was obtained using one of the commercially available HRM systems. Thus, it is of great importance to evaluate whether these normative values can be used for other HRM systems as well. In this review, we describe the presently available HRM systems, the currently known normative thresholds and the factors that influence them, and assess the use of these thresholds. Numerous factors including the type of HRM system, demographic factors, catheter diameter, body position during testing, consistency of bolus swallows, and esophageal length have an influence on the normative data. It would thus be ideal to have different sets of normal values for each of these factors, yet at the moment the amount of normative data is limited. We suggest broadening the normal range for parameters, as this would allow abnormal values to be of more significance. In addition, we suggest conducting studies to assess the physiological relevance of abnormal values and stress that for each system different normative thresholds may apply