Estimation of bladder contractility from intravesical pressure-volume measurements

To describe parameters from urodynamic pressure recordings that describe urinary bladder contractility through the use of principles of muscle mechanics.

Subtracted detrusor pressure and voided flow were recorded from patients undergoing filling cystometry. The isovolumetric increase of detrusor pressure, P, of a voluntary bladder contraction before voiding was used to generate a plot of (dP/dt)/P versus P. Extrapolation of the plot to the y-axis and the x-axis generated a contractility parameter, v_CE (the maximum rate of pressure development) and the maximum isovolumetric pressure, P₀ , respectively. Similar curves were obtained in ex vivo pig bladders with different concentrations of the inotropic agent carbachol and shown in a supplement.

Values of v_CE , but not P₀ , diminished with age in female subjects. v_CE was most significantly associated with the 20-80% duration of isovolumetric contraction t_20-80 ; and a weaker association with maximum flow rate and BCI in women. P₀ was not associated with any urodynamic variable in women, but in men was with t_20-80 and isovolumetric pressure indices.

The rate of isovolumetric subtracted detrusor pressure (t_20-80 ) increase shows a very significant association with indices of bladder contractility as derived from a derived force-velocity curve. We propose that t_20-80 is a detrusor contractility parameter (DCP). Neurourol. Urodynam. 36:1009-1014, 2017. © 2016 Wiley Periodicals, Inc.