A new catheter to measure urethral compliance in females: normal values

We describe a new probe made of several F5 Vinyl tubes glued and staggered together in such a way that the catheter progressively increases in size (from F5 to F30), as more tubes are joined. At each size, pressure is recorded through a single side hole in one of the tubes. Pressure within the urethra is thus successively recorded from F5 to F30 as the catheter is further introduced. A single pressure transducer is used since the lines of the probe are separately and successively connected to the transducer through a 6-channel manifold, as one proceeds to the next diameter. Pressure diameter curves are obtained and reported on a graph. The data are analyzed by fitting the graphs with a one exponential equation P = PoeaD; 2 parameters are computed: Po, the initial pressure when the urethra is catheter free, and a, the rate of exponential increase in pressure as higher diameters are introduced to measure urethral wall stiffness. This catheter was used to measure the maximum urethral pressure in 10 young nulliparous volunteers, at each level of stretch. The values of Po and a were found to be respectively 74.4 +/- 7.7 cm. H2O and 0.08 +/- 0.02. The quantitative measurement of urethral compliance constitutes for us an integral part in the urodynamics assessment of female patients presenting with lower urinary tract dysfunction.