Static single channel and multichannel water perfusion pressure profilometry in a bench model of a urethra

To determine the catheter perfusion and withdrawal rate which generate the most repeatable single (SCPP) and multichannel pressure profilometry (MCPP) profiles in a bench model.

A bench model using a urethral substitute was developed in which SCPP and MCPP were performed using the Brown-Wickham method. One single channel and four multichannel catheters were tested using seven withdrawal rates and three perfusion rates. Repeatability was determined using spread of mean profile pressure, cross-correlation, Bland-Altman statistic, and a one-tailed Student's t-statistic. An artificial urinary sphincter (AUS) model was constructed to create a predictable intraluminal profile. MCPP data were used to generate three-dimensional (3D) images of the pressures exerted by the AUS model.

A withdrawal rate of 0.5 mm/sec and perfusion rate 1 ml/min produced the most repeatable SCPP profiles with a spread of mean profile pressure ≤7 cmH(2)O. For MCPP, a 10 F 6-channel catheter using a withdrawal rate of 1 mm/sec and perfusion rate of 1 ml/min produced the most similar profiles (cross-correlation = 0.99). However, the spread of MCPP was large (spread ≤44 cmH(2)O per channel). Nevertheless MCPP was able to consistently demonstrate areas of high pressure as predicted by the AUS model.

MCPP was not repeatable and is an unreliable measure of urethral pressure. MCPP and 3D images do demonstrate directional differences predicted from the AUS model. These may be of use for qualitative understanding and appreciation of relative relationships if not actual forces within the urethra and have application in understanding urethral function in vivo.