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

The calculation and comparison of the Detrusor Contractility Parameter and Watts Factor

“…The value of t 20-80 , in the isovolumic phase of the rise of P det during a voiding contraction, was suggested as a surrogate of v CE due to the excellent association between the two in both men and women, 2 and labelled the Detrusor Contractility Parameter (DCP). It has been pointed out that t 20-80 can be influenced by outflow resistance 14 and this should be particularly so in men, for whom prostatic obstruction is a common problem. This is supported by the less significant association of v CE and t 20-80 in men (Table 1) and also by the positive association between BOOI and t 20-80 .…”

“…Another factor needing investigation is the effect of bladder shape on this parameter. The assumption of continual spherical shape is unlikely to be true, 14 and the resultant effect on the DCP is unknown and should be quantified. Additionally, for many patients, there is negligible rise time, or even negligible P det rise, before flow starts, so DCP cannot be used in their case.…”

“…2 DCP was compared with BCI, Q max and age, but not with W max . The use of t 20-80 , whilst convenient, may be criticized 14 as it could be dependent on outflow tract opening pressure and resistance, which if increased would prolong the isovolumic phase. This study therefore aimed: to test the association between v CE and the Watts Factor; and to test whether t 20-80 depends on outflow tract resistance.…”