Estimation of bladder contractility from intravesical pressure–volume measurements

Abstract

Aims To describe parameters from urodynamic pressure recordings that describe urinary bladder contractility through the use of principles of muscle mechanics. Methods 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, vCE (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. Results Values of vCE, but not P0, diminished with age in female subjects. vCE was most significantly associated with the 20–80% duration of isovolumetric contraction t20–80;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 t20–80 and isovolumetric pressure indices. Conclusions The rate of isovolumetric subtracted detrusor pressure (t20–80) increase shows a very significant association with indices of bladder contractility as derived from a derived force–velocity curve. We propose that t20–80 is a detrusor contractility parameter (DCP).

Are there different patterns of detrusor overactivity which are clinically relevant? ICI‐RS 2018

“…The second is the shape and frequency content of an individual DO wave. Analysis of this second pattern group, better described as DO wave shape, is more complex, but methods of analysis that have been proposed are Fast Fourier Transform frequency analysis, high definition ultrasound of the bladder wall , and advanced analysis of the rate of muscle fibre contraction . Automated procedures need to be developed and validated before reliable classification of DO wave shape can be achieved.…”

Re: Fry et al. Estimation of bladder contractility from intravesical pressure-volume measurements

“…In 1978, van Duyl et al suggested to use (dp/dt × 1/p) max as a detrusor contractility parameter in analogy to cardiac contractility assessment. Thus, Fry et al are misleading when presenting this as a new concept. Further, a variety of similar parameters using pressure gradients have been evaluated comprehensively on clinical urodynamic data and in animal experiments .…”

“…However, the determination of such contractility parameters, particularly from the pressure rise preceding flow at normal micturition and more so at stop‐tests and with detrusor overactivity yielded highly variable values, indicating that basic assumptions are not met and that it is not a true maximum isometric contraction . Unfortunately these most important shortcomings are not taken into account with respect to DCP …”

“…Here, a new detrusor contractility parameter (DCP) is suggested from most prominent authors, so that a very close look is indicated. At first glance, this complex publication appears to tie in to the many publications on contractility from the 1970s to 1980s when detrusor contractility was comprehensively investigated.…”

“…However, a short look at the references shows that most relevant publications of this time, like from Berg, Byrne, Coolsaet, Griffiths, Schäfer, van Duyl, van Mastrigt, and many others, are not taken into consideration . A careful review of this DCP reveals that relevant shortcomings affecting the rate of pressure change and the t 20‐80 are ignored …”