Figure 3: SPWs, internal anal sphincter relaxation and artifactual pressurization.
From: Intraluminal pressure patterns in the human colon assessed by high-resolution manometry
(A) Rhythmic SPW activity at 1 cycle/min of variable amplitude. The internal anal sphincter relaxes upon an approaching SPW, even those of relatively low amplitude. The relaxation can be seen to precede the arrival of the SPW. From a patient with constipation; sensor P1 and P2 are at the internal anal sphincter. A cough at ~2.5 min leads to a simultaneous pressure change but is not associated with sphincter relaxation. The last two SPWs were associated with gas expulsion. (B) Identification of artifacts due to abdominal pressure changes. Turning of the body from one side to the other causes marked changes in abdominal and intraluminal pressure and has to be noted at all times during the motor function test. Coughs cause sharp simultaneous pressure increases not resembling in any way the SPWs. Talking rarely gives noticeable pressure changes. All data are from a patient with constipation; sensor P36 is 85 cm from anal verge.
