Noninvasive quantitative method for measuring isovolumetric bladder pressure and urethral resistance in the male: I. Experimental validation of the theory

Abstract

Noninvasive measurement of intravesical pressure, impulsive flow rate, and localized urethral resistance is achieved by clamping the penis immediately above the glans with a pneumatic cuff and then instructing the patient to initiate voiding. The cuff is then deflated slowly until urinary flow of at least 1 ml/s is detected and is then released rapidly to permit unimpeded flow. Cuff pressure, voided volume, and flow rate are recorded as functions of time. From the resulting tracings it is possible to determine the isovolumetric bladder pressure, the impulsive flow rate, and the flow pattern specific to the test. We studied 53 male patients demonstrating that data thus obtained are reproducible and that the cuff pressure at the initiation of voiding does measure the bladder pressure at this moment. We then modeled the lower urinary tract by an analog electrical circuit which facilitated the analysis of the urodynamic data. This analysis suggests that it is possible to separate the effects of bladder dysfunction from the effects of urethral resistance and to localize the resistance to the proximal or distal urethra without invasive testing.

Noninvasive urodynamics: A study of male voiding dysfunction

“…The CUF report included the values of isovolumetric pressures at the inception of flow (P iso ) in cm H 2 O, maximum urethral carrying capacity (Q i ) in ml/sec following the initial surge with cuff release, and the pattern of the flow curve as outlined previously [McRae et al, 1995a]. The energy transfer ratio was calculated as R ‫ס‬ P iso /Q i 2 , with R increasing with severity of obstruction.…”

“…In a previous paper [McRae et al, 1995a] we explained the cuff-uroflow (CUF) technique of measuring isovolumetric bladder contraction pressure (P iso ), and the corresponding optimal flow rate (Q i ), noninvasively. In the present paper we exploit this technique to obtain clinically useful diagnostic information about a cohort of 26 male patients with voiding problems.…”

Noninvasive Methods to Evaluate Bladder Obstruction in Men

“…Non-invasive pressure-flow studies may be performed using an external modified condom catheter (39,40). A pressure transducer may be attached to the open outlet of a condom catheter.…”

“…A cuff is occluded around the urethra prior to voiding, then released to allow voiding and measure the pressure (40,41,43). A cuff fitted around the penile shaft is inflated to 250 cmH2O, then the subject in instructed to void against the occluded urethra.…”

“…In one study, where subjects also underwent invasive pressure-flow studies, cuff pressures were higher than measured intravesical pressure. This was accounted for by differences in height between the pressure transducer and the penile cuff (40).…”