MUCOSAL ACID EXPOSURE SENSITIZES A SUBSET OF NORMAL SUBJECTS TO INTRA-ESOPHAGEAL BALLOON DISTENSION

Object: To assess the effect of acid infusion on the response of norma l subjects to progressive intra-oesophageal balloon distension (IOBD). Methods: Twenty-one volunteers underwent slow IOBD. Subjects were ask ed to indicate the first perception of sensation (S1) and the onset of pain (S2), balloon volumes being recorded at both points. A 15-min in fusion of 0.1 M HCl (8 ml/min) was then instilled proximal to the ball oon. Subjects were designated as acid-sensitive if they reported chest pain or heartburn during the acid infusion. Thereafter S1 and S2 were assessed again in the same manner. Results: Nine subjects were acid-s ensitive, 12 were acid-insensitive. The subgroup of 12 acid-insensitiv e subjects had an increase of pain threshold after acid infusion (P <0 .05), whereas the nine acid-sensitive subjects showed a decrease of pa in threshold after acid infusion (P <0.05). No change of the threshold for sensation occurred in either of these groups after acid infusion. Conclusion: Individuals showing mucosal acid sensitivity have a lower threshold for mechanoreceptor stimulation after acid exposure.