Quantification of urethral function based on Griffiths' model of flow through elastic tubes

Griffiths' model of flow-through elastic tubes makes it possible to relate the elastic properties of the flow-controlling zone to the pressure/flow relation of the urethra. In this work the pressure function p(A) = P_mo + K_n Aⁿ, where A is cross-sectional area, P_mo the minimal opening pressure, and K_n and n parameters describing urethral distensibility, describes the elastic properties of the flow-controlling zone. By curve-fitting in the pressure/flow plot, the three parameters p_mo, K_n, and n can be estimated analytically. Using this model it is possible to identify three different biomechanical changes that may cause obstruction. First, p_mo may be elevated. Second, the urethra can be distended to a certain area only, corresponding to high values of K_n and n. Third, the urethra can be distended but a higher-than-normal pressure increase above P_mo is needed, K_n is high, and n is low. With this model it is possible to quantify urethral function for both scientific and clinical purposes.