STUDIES OF VISCERAL PAIN: MEASUREMENTS OF STIMULUS INTENSITY AND DURATION ASSOCIATED WITH THE ONSET OF PAIN IN ESOPHAGUS, ILEUM AND COLON

Abstract

The relationship between intensity and duration of stimulus required to produce pain in the esophagus, ileum and colon was studied in 51 subjects. Intubation of the organ was performed with balloon and catheter. The balloon-catheter system was attached to a water chamber characterized by a large cross-sectional area at the fluid surface. The intensity of the stimulus was measured as the height of water in the chamber, and the height of water did not measurably change during each experimental determination. The duration to the earliest perceptible sensation of pain was measured. A relationship of stimulus intensity and duration existed for onset of visceral pain, which is similar to that for cutaneous pain. Intensity-duration curves for the 3 organs were similar. Differences in rheobase values were believed to be due to properties intrinsic in the tissues and to variations in the rate of distension of the segment of viscus. The mean duration to colonic pain threshold in 37 subjects studied at a single stimulus intensity was 6.6 seconds with a standard deviation of [plus or minus] 3.6 seconds. Repeated observations made on 4 subjects with several weeks between experiments revealed little variation in pain threshold for each subject. Comparison of the characteristics of intensity-duration curves obtained from measurements of visceral and cutaneous pain, revealed the possibility that changes of local tissue accommodation prevent the onset of both varieties of pain.