A psychophysiological study in humans using phasic colonic distension as a noxious visceral stimulus

TLDR

Nine healthy volunteers underwent constant‑pressure, phasic, graded sigmoid‑colon distension (30 s, 20–70 mm Hg) while pressure/pain sensations were referred to the lower abdomen, lower back and perineum and quantified with a visual analogue scale. Colonic distension reliably evoked cardiovascular, respiratory, visceromotor, and sensory responses in 8 of 9 subjects, with graded increases in intensity, area of referral, and affective descriptors upon repeated distensions, and five subjects distinguished pressure from pain sensations, the latter accelerating during distension.

Abstract

Psychophysiological experiments were performed in 9 humans using constant-pressure, phasic, graded distension (30 sec, 20–70 mm Hg) of the sigmoid colon as a visceral stimulus. Reliable cardiovascular (pressor), respiratory and visceromotor responses in addition to reports of pressure/pain sensations were evoked by colonic distension in 8 of the 9 subjects. The pressure/pain sensations were referred to the lower abdomen, lower back and perineum and their intensity quantified using a visual analogue scale. Responses to colonie distension were graded and increased with repeated distensions at the same intensity (60 mm Hg). The area of referral as indicated by subject drawings increased with repeated distensions as did the intensity of the subjects' sensory and affective descriptors of the sensation. Five of the subjects differentiated between ‘pressure’ and ‘pain’ sensations evoked by colonic distension; the intensity of the ‘pain’ sensation accelerated during the distending stimulus whereas the ‘pressure’ sensation was typically stable or adapting during the distending stimulus.