AJP - Heart and Circulatory Physiology, Vol 269, Issue 6 2109-H2123, Copyright © 1995 by American Physiological Society
Assessment and modeling of the physical components of human corporovenous function
J. G. Venegas, M. P. Sullivan, S. V. Yalla and M. A. Vickers Jr
Division of Urology, West Roxbury Veterans Affairs Medical Center, Boston, Massachusetts, USA.
To understand and quantify specific causes of venoocclusive dysfunction, an
analog model of penile hemodynamics, including a mechanism of flow
limitation by subtunical veins, was developed and a detailed analytic study
was conducted in patients with erectile dysfunction. Computer simulations
for steady-state and transient intracavernosal conditions were carried out
to study graded changes in cavernosal smooth muscle tone, subtunical
venular resistance, and cavernosal and tunical compliances. The model
predicted a steady-state cavernosal pressure (Pca)-infusion flow
relationship with two phases: an initial phase characterized by a gradual
slope up to a critical flow and a second phase characterized by a much
steeper slope after limitation of subtunical venular flow. Model
predictions were compared with clinical data obtained during incremental
saline cavernosometry (SaC) and pharmacocavernosometry (PhC) in 13 patients
with erectile dysfunction with use of a computer-controlled infusion system
that automatically changed from constant-flow to constant-pressure feedback
control when Pca reached the threshold of 80 mmHg. Steady-state
pressure-flow and pressure-circumference relationships of the penis were
analyzed and interpreted in terms of specific components of the electrical
analog model. These clinical studies demonstrated that patients with a
functional venoocclusive mechanism (i.e., those able to achieve 100 mmHg
Pca with infusion flow rates < 60 ml/min during PhC) had a steeper
initial slope of the pressure-flow relationship during SaC and a greater
increase in penile circumference and Pca after intracavernosal injection of
papaverine-phentolamine than those with an impaired venoocclusive
mechanism. From the electrical analog model, initial steepness of the
pressure-flow relationship (slope) during SaC mainly represented subtunical
venular resistance, whereas maintenance of flow during PhC depended on
overall function of the different components, i.e., subtunical venular
resistance, cavernosal and subtunical compliances, and full relaxation of
cavernosal smooth muscle. We conclude that the proposed analog model can be
used to interpret and characterize clinical penile hemodynamic data and may
provide guidelines for more successful management of patients with erectile
dysfunction.
