Differences between water-filled and air-charged urodynamic catheters for determining the urethral pressure profile in neurogenic bladder patients
Dr. Yi Gao (1), Dr limin Liao, Dr haitao Zhao
(1) China Rehabilitation Research Center, beijing, China
The maximum urethral closure pressure and functional urethral length obtained with water-filled and air-charged catheters during urethral pressure profile determination was compared in a single-blind, randomized, prospective trial.
Thirty-three males with spinal cord injuries and neurogenic bladders underwent urethral pressure profile determinations using water-filled and air-charged catheters in a 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. Person’s correlation coefficient was used to check the correlation between the catheters and the Bland-Altman method was used to verify the agreement.
The intra-class correlation coefficients for maximum urethral closure pressures and functional urethral lengths determined using water-filled and air-charged catheters were 0.89, 0.75, 0.94, and 0.78, respectively. The interclass correlation coefficients for maximum urethral closure pressures and functional urethral lengths 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 cmH2O and2.4 cm, respectively). There were wide 95% limits of agreement [95% confidence limits?] (-54.0 to106.0 cmH2O and -0.3 to5.1 cm, respectively) that exceeded the clinical range for differences in maximum urethral closure pressure and functional urethral length.
Air-charged catheters are suitable for urethral pressure profile determination and usually give higher readings than water-filled catheters. Agreement between water-filled catheters was not good. Nevertheless, the catheter type which is more relevant to the disease requires further study. Air-charged and water-filled catheters are not interchangeable and clinicians should consider catheter type when interpreting the results.