Cortical evoked potentials in response to stimulation of the oesophagus may prove to be a powerful technique for assessing the oesophageal afferent pathway in health and disease. However, in order to maximize the potential of this technique it is essential that the optimal parameters for recording oesophageal CEP are established. The aim was to determine the optimal parameters required to record reproducible CEP. CEP were recorded from the vertex in eight subjects (age range 23-44 years). Electrical stimulation was performed 5 cm above the lower oesophageal sphincter using a bipolar ring electrode at 0.2 Hz. Protocol 1: to determine the stimulation intensity which generates the largest amplitude and shortest latency, two runs of 50 stimuli were applied at increasing intensities. Protocol 2: to determine the number of stimuli for optimal signal to noise ratio, 10 runs of 50 stimuli were recorded. Individual runs were averaged. Protocol 3: to determine the optimal inter-run interval, CEP evoked by 200 stimuli were averaged using randomly chosen inter-run intervals. Protocol 4: CEP reproducibility using parameters determined from Protocols 1-3 was assessed in three subjects on three separate occasions. The results were as follows: Protocol 1; P1 latency was shortest and P1-N1 amplitude largest at an intensity of 75% above threshold. Protocol 2; optimal signal-to-noise was achieved by averaging four runs of 50 stimuli. Protocol 3; the optimal interstudy interval was 10 min. Protocol 4; highly reproducible CEP were obtained in all individuals. Using these optimal parameters, it is possible to obtain highly reproducible oesophageal CEP to ES which can now be used for clinical study.

A computer-controlled tensiometer for studying wall tension in tubular organs has been developed. The system consisted of a probe with an inflatable balloon, an impedance planimeter, pressure transducer and amplifier, a pump with RS232 interface and a PC with dedicated software. Circumferential wall tension was computed in real time from pressure and cross-sectional area measurements (tension measurement mode). Wall tension can be maintained on a preset level or be changed as a step or ramp function by a feedback control of the infusion/withdrawal pump (tension control mode). A software regulator adjusted the volume rate (low volume rate when the computed tension was close to the preset value) to minimize overshoot and oscillation. Validation tests were performed and the technique was applied in the human oesophagus. Volume- and tension-controlled balloon distensions elicited secondary peristalsis of increasing intensity that was decreased significantly by the antimuscarinic agent Hyoscine butyl bromide. In tension control mode Hyoscine butyl bromide caused oesophageal relaxation, i.e. CSA to increase and pressure to decay. Furthermore, pronounced pressure relaxation and tension relaxation were observed during volume-controlled distension after administration of Hyoscine butyl bromide.

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