HUMAN ANAL MOTILITY WHILE FASTING, AFTER FEEDING, AND DURING SLEEP

The aim of this study was to determine whether the human anal sphincter responds dynamically to changing physiological states. In 19 healthy human subjects, intraluminal anal canal pressure was measured with a 5-cm perfused sleeve sensor during the day while fasting (3 hours) and after feeding (3 hours) and at night during sleep (8 hours). Daytime mean anal canal pressures (± SEM) while fasting (50 ± 3 mm Hg) were similar to those after feeding (49 ± 3 mm Hg) and to those at night during sleep (49 ± 3 mm Hg). Marked minute-to-minute variations in mean pressure occurred in all three periods, however, as did large phasic increases and decreases in pressure (> 20 mm Hg) and small phasic changes in pressure < 20 mm Hg (anal slow waves). The minute-to-minute variations in mean pressure were greater during the awake fed state (4 ± 1 mm Hg/min) than at night during sleep (2 ± 1 mm Hg/ min; P < 0.03), as were the number of large phasic waves per minute (increases in pressure: awake, fed = 0.5 ± 1 waves/min, night = 0.3 ± 0.1 waves/ min, P < 0.05; decreases in pressure: awake, fed = 0.4 ± 0.1 waves/min, night = 0.2 ± 0.1 waves/ min, P < 0.05). Anal small waves had a similar frequency of about 17 waves/min in all three states. In conclusion, the anal sphincter maintains a continuous pressure barrier to rectal outflow both during the day and at night during sleep. However, marked minute-to-minute variations in mean pressure and large phasic increases and decreases in pressure do occur. Both are fewer at night during sleep. © 1991.