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This study monitored high-amplitude propagated contractions (HAPCs) in ambulating subjects over a 24-h period using a new ambulatory recording system. Twelve healthy volunteers aged 34 +/- 5.96 yr participated. Approximately 12 h after a Colyte bowel prep, a small catheter (OD less than 3 mm), containing three solid-state pressure transducers spaced 5 cm apart, was positioned by flexible sigmoidoscope at 40-50 cm from the anal verge. A battery-operated data recorder sampled the pressure at each port at 1 Hz and stored the values on all ports if any port exceeded 75 mmHg. At the conclusion of the 24-h period, an X-ray was taken to confirm the location of the catheter. Fifty-four percent of all HAPCs preceded a bowel movement by less than or equal to 1 h. Forty-nine percent of all HAPCs occurred within 1 h after a high-fat meal, and 33% occurred within 1 h of morning awakening. Reverse propagated waves, not previously described in the colon, were observed in three individuals. Spontaneous high-amplitude caudally propagated contractions occur 6.9 +/- 1.5 times/24 h in the sigmoid colon in ambulating asymptomatic individuals and are temporally related to defecation and meals. Peristaltic activity is decreased during sleep. This recording technique was reliable and well tolerated in all participants.

A pattern-recognition program was developed which emulates visual scoring of colonic myoelectric and pressure recordings. It smoothes digitized data with a moving average filter, computes difference scores between successive groups of three data points, and uses the signs of these difference scores to detect the beginning and end of waves. Adjacent waves are merged if their means are closer than 1.67 times the sum of their standard deviations, and amplitude and duration criteria are used to exclude nonsignificant waves. When compared to four experienced human scorers on randomly selected records, the program agreed as well with the human scorers as they agreed with each other, and it approached the level of agreement of these observers with themselves when they were asked to rescore the same records blindly four to six weeks later. Human scorers agreed with themselves on 36-71% of myoelectric slow waves and on 42-88% of pressure waves, compared to 100% test-retest reliability for the pattern-recognition program. Frequency histograms of the duration of waves detected by the pattern-recognition program differed from the spectra generated by the fast Fourier transform (FFT) method. This pattern-recognition program provides an alternative to spectral analysis for the reliable and objective quantification of colonic myoelectric slow waves and pressure waves.

Colon motility and myoelectric slow wave activity were compared in 10 patients with progressive systemic sclerosis and 18 controls. Recordings were made in the rectosigmoid and rectum, 25-30 cm and 10-15 cm from the anal margin, respectively, during two 4-min baselines and in response to stepwise distention of the colon with an air-filled balloon. During baseline, the motility (activity index, defined as cumulated areas of all waves divided by recording time) of the rectosigmoid was similar in patients with progressive systemic sclerosis (0.38 +/- 0.61 in baseline 1, 0.86 +/- 1.33 in baseline 2) and controls (1.15 +/- 2.02 in baseline 1, 0.77 +/- 1.01 in baseline 2). Rectal motility was also similar during baseline in patients with progressive systemic sclerosis (1.43 +/- 2.56 in baseline 1, 1.65 +/- 2.47 in baseline 2) and controls (0.56 +/- 0.80 in baseline 1, 0.62 +/- 0.94 in baseline 2). Patients showed a lower tolerance for balloon distention of the colon (average, 130 vs. 184 ml) and a greater amount of contractile activity than controls after balloon distention (rectosigmoid activity index, 1.05 +/- 1.24 vs. 0.07 +/- 0.14; rectal activity index, 2.75 +/- 3.71 vs. 0.13 +/- 0.31). Maximum tolerable volume of balloon distention was inversely correlated to complaints of diarrhea in patients. Slow wave myoelectric activity did not differentiate patients from controls. These findings suggest that diarrhea, and possibly other gastrointestinal symptoms associated with progressive systemic sclerosis, may be due to decreased compliance of the bowel.

Patients with different irritable bowel symptoms and normal subjects were compared to determine whether subtypes of irritable bowel syndrome (IBS) could be distinguished on the basis of colonic motility or psychological test scores. A provocative test involving stepwise distension of the rectosigmoid area revealed two types of colonic motility. Slow contractions having durations of at least 15 sec and occurring at irregular intervals were more frequent in IBS patients than in normals but did not differentiate constipation from diarrhea. Fast contractions having durations of less than 15 sec and occurring in runs at frequencies of 6-9 cpm were more frequent in patients with diarrhea than in normals or constipated IBS patients. Constipated patients showed no more fast contractions than normals. Severity of bowel symptoms was correlated with the overall amount of motility (motility index) in patients with diarrhea but not in patients with constipation. Patients with IBS showed significantly elevated levels on the following psychological traits: anxiety, interpersonal sensitivity, depression, hostility, and somatization of affect. However, there were no significant trait differences between patients with diarrhea and those with constipation. Also, there was no correlationbetween amount of psychopathology and either colonic motility or severity of symptoms in the whole group of IBS patients.