Normative values and inter-observer agreement for liquid and solid bolus swallows in upright and supine positions as assessed by esophageal high-resolution manometry

Background High-resolution manometry (HRM) with spatiotemporal representation of pressure data is a recent advance in esophageal measurement. At present, normal values are available for 5 mL water swallows in the supine position. This study provides reference values for liquid and solid bolus swallows in the upright seated and supine positions. Methods A total of 23 asymptomatic volunteers (11M : 12F, age 20-56) underwent HRM (Manoscan 360; Sierra Scientific Instruments) with 5 mL water and 1 cm(3) bread swallows in the upright and supine positions. Normal values for primary parameters associated with effective bolus transport [proximal transition zone length (PTZ, assesses peristaltic coordination], contraction front velocity (CFV), distal contractile index (DCI) and integrated relaxation pressure (IRP)] are presented. For each parameter, median values along with the 5-95th percentile range are reported. Interobserver agreement between independent observers is reported using the intra-class correlation coefficient. Key Results A higher proportion of swallows were peristaltic for liquids than solids in both the upright and supine positions (both P < 0.05). As workload increases with solid bolus and on moving from the upright to the supine position the esophageal contractile response resulted in a shorter PTZ, a slower CFV, and a more vigorous DCI. Also IRP increased during solid bolus transit (all P < 0.01). There was significant agreement between independent observers for HRM parameters. Conclusions & Inferences Normative values for esophageal function for solids as well as liquids and in the 'physiologic', upright position will optimize the utility of HRM studies. The high level of inter-observer agreement indicates that these can be applied as reference values in clinical practice.