Model-based estimation of urethral resistance and elasticity using urodynamic pressure-flow data

A lumped parameter model of the urethra was developed to assess urethral resistance and changes in urethral elasticity during voiding using pressure and flow measurements. The model includes a pressure drop due to rapid velocity change in the constricted flow-controlling zone and urethral elasticity relating cross-sectional area with pressure. Using real pressure-flow data sets, the model was used to estimate urethral resistance and changes in urethral elasticity during voiding. Results show that it is possible to obtain resistance and estimate changes in elasticity during voiding from the pressure and flow. Estimations of elasticity show that in the normal patient relaxation of the urethra is a process that continues until end of voiding. This has important implications regarding present methods that are used in the clinic to assess urethral obstruction or constriction.