The Esophageal Multimodal Pain Model: Normal Values and Degree of Sensitization in Healthy Young Male Volunteers

Abstract

Sensory changes are thought to be involved in gastro-esophageal reflux disease (GERD). The esophageal multimodal pain model can be used to investigate sensations in response to distension, heat, electric current and acid. The aim of this study was to provide normal values for this model in the normal state and in the acid induced sensitized state. Fifty-three healthy men (20-38years old) underwent esophageal stimulation with distension, heat and electrical current before and after sensitization with 0.1N HCl acid. Stimulus intensities at painful and non-painful thresholds and referred pain areas were measured. The percentage of individual participants sensitized to each modality was calculated. In 22 subjects the pre-acid tests were repeated on three subsequent visits. To reach moderate pain, subjects tolerated mean distension of 29.1±11mL, heat stimulation time of 141±33s, and mean current of 17.6±6.4mA. After acid exposure, significantly reduced thresholds were observed for mechanical (24%), heat (11%) and electrical (14%) stimulation (P values<0.05). The percentage of subjects sensitized, defined as reductions in thresholds of≥10% or≥20% after acid perfusion, was as follows: for distension 77%/62%, for heat 48%/28%, and for current 58%/44%. The model showed good reliability (intra-class correlations>0.6). Normal values for healthy young men are now provided for the normal and the sensitized state. The percentage of subjects sensitized after acid stimulation are thoroughly documented, and depends on stimulation type and the cut-off value chosen.