Significance of the pressure waves of the sigmoid colon

Abstract

p RESSURES have been recorded from the large intestine for a number of years with the use of several different recording systems. In general, investigators in earlier studies used large balloons with the appropriate manometer system, 1, 2 but in more recent studies, open ended tubes ~, 4 or miniature balloons have been used. 5 The results of these studies are complementary and permit a dearer understanding of the nature of the activity of the lower colon. Studies of the right side of the colon are not as advanced as those of the left, but the advent of radio telemetering of gastrointestinal pressures has made it possible to study the right side of the colon with the same ease and accuracy as the left. 6 MAJOR FEATURES OF PRESSURE RECORD PRINCIPAL WAVES The most constant feature of pressure recordings of the sigmoid colon is principal waves2 which represent slow pressure changes over a 20-to30-see. period, with an amplitude varying from less than 5 to more than 100 cm. of water pressure. They are frequently simple waves but, not uncommonly-, bifid or complex forms are seen (Fig. 1). Their distribution is irregular. They may occur singly or, more often, in phases of activity which alternate with periods of relative or complete inactivity. The duration and proportion of the active and inactive periods varies widely, but the periodicity of the cycles is usually less than 30 min. although periods of complete quiescence lasting 1 hr. or more can occur. When the waves occur in rhythmic sequence, the frequency of contraction is approximately 2 waves per minute.