Differences between water-filled and air-charged urodynamic catheters for determining the urethral pressure profile...

The maximum urethral closure pressure (MUCPs) and functional urethral length (FUL) obtained with water-filled and air-charged catheters during urethral pressure profile (UPP) determination was compared in a single, blind, randomized, and prospective trial.

Thirty-three males with spinal cord injuries and neurogenic lower urinary tract dysfunction underwent UPP determinations using water-filled and air-charged catheters in random order; the patients were unaware of the catheter sequence. The variability of the same type of catheter and the agreement between the different types of catheters were compared. The Pearson correlation coefficient was used to check the correlation between the catheters and the Bland-Altman method was used to verify the agreement.

The intraclass correlation coefficients for MUCPs and FULs determined using water-filled and air-charged catheters were 0.89, 0.75, 0.94, and 0.78, respectively. The interclass correlation coefficients for MUCPs and FULs between the two catheters were 0.43 and 0.28, respectively. Bland-Altman plots suggested that the values measured by air-charged catheters were significantly higher than water-filled catheters (mean difference, 26.0 and 2.4 cmH₂ O, respectively). There were wide 95% limits of agreement (-54.0 to 106.0 and -0.3 to 5.1 cmH ₂ O, respectively) that exceeded the clinical range for differences in MUCP and FUL.

Air-charged catheters usually give higher readings than water-filled catheters for UPP. Agreement between water-filled and air-charged catheters was not good. Nevertheless, the catheter type which is more relevant to the disease requires further study.