OBJECTIVE: To determine which urodynamic model best describes lower urinary tract dynamics during the voiding phase. METHODS: A pressure-flow study was conducted in 211 adult males. The urodynamic data from the pressure-flow study were modelized to a multivariate analysis with a descriptive design. Three descriptive models of urethral resistance were proposed: a linear model that consisted of the detrusor pressure at the end of voiding and the pressure-flow plot slope, and two quadratic models with one parameter [urethral resistance average (URA)] or two parameters [opening detrusor pressure and passive urethral resistance ratio curvature (PURR)]. Bladder contractility was defined by two parameters: power at maximum flow rate (Pw) and maximum power/bladder surface (Wmax). Voiding volume was included in all models as control variable. The best model was defined as that which explains a higher percentage of observed maximum urinary flow rate, the most widely utilized datum in the urodynamic studies of the adult male. RESULTS: The model that consisted of the URA and Pw was found to be the best. We observed an interaction between URA and voiding volume (at higher voiding volume the decrease of the maximum urinary flow due to URA was found to be greater). CONCLUSIONS: The URA was found to be the parameter that best describes urethral pressure. Variations in the maximum urinary flow rate is better described by the Pw than by the Wmax.
OBJECTIVE: To determine which urodynamic model best describes lower urinary tract dynamics during the voiding phase. METHODS: A pressure-flow study was conducted in 211 adult males. The urodynamic data from the pressure-flow study were modelized to a multivariate analysis with a descriptive design. Three descriptive models of urethral resistance were proposed: a linear model that consisted of the detrusor pressure at the end of voiding and the pressure-flow plot slope, and two quadratic models with one parameter [urethral resistance average (URA)] or two parameters [opening detrusor pressure and passive urethral resistance ratio curvature (PURR)]. Bladder contractility was defined by two parameters: power at maximum flow rate (Pw) and maximum power/bladder surface (Wmax). Voiding volume was included in all models as control variable. The best model was defined as that which explains a higher percentage of observed maximum urinary flow rate, the most widely utilized datum in the urodynamic studies of the adult male. RESULTS: The model that consisted of the URA and Pw was found to be the best. We observed an interaction between URA and voiding volume (at higher voiding volume the decrease of the maximum urinary flow due to URA was found to be greater). CONCLUSIONS: The URA was found to be the parameter that best describes urethral pressure. Variations in the maximum urinary flow rate is better described by the Pw than by the Wmax.