A pharmaco-cavernosometry based clinical study was designed to define hemodynamic parameters consistent with complete trabecular smooth muscle relaxation, establish a methodology for overcoming incomplete trabecular smooth muscle relaxation, and determine under controlled conditions the contribution of venous outflow and arterial inflow to the steady-state equilibrium intracavernous pressure. Flow-pressure relationships were analyzed in 21 patients each of whom was assumed to have complete smooth muscle relaxation by virtue of the full, rigid and maintained erectile response following intracavernous vasodilator administration, which required intracavernous adrenergic agonists to achieve detumescence. Flow-to-maintain values increased linearly with intracavernous pressure while venous outflow resistance values were high and constant. Based on these relationships, trabecular smooth muscle tone was assessed in 123 impotent patients. In 14%, 63% and 14% of the patients (112 of 123 overall), respectively, 1, 2 and 3 doses of vasoactive agents were required to achieve hemodynamic relationships consistent with complete trabecular smooth muscle relaxation. In 9% of the patients such hemodynamic relationships were unable to be reached. In the 112 patients the influence of different engineering based measures of corporeal veno-occlusive function, including flow-to-maintain, pressure decay, venous outflow resistance and corporeal capacitance, was analyzed against the spectrum of equilibrium steady-state intracavernous pressures. Two distinct equilibrium pressure groups were identified reflecting different capacitance states: pressures greater than 60 mm. Hg (associated with low capacitance values) and pressures less than 50 mm. Hg (associated with high capacitance values), with pressures 50 to 59 mm. Hg representing a hemodynamic transition zone. When analyzed during complete trabecular smooth muscle relaxation, corporeal veno-occlusive hemodynamic variables in conjunction with cavernous arterial perfusion pressure determine the steady-state equilibrium intracavernous pressure. Failure to assess corporeal veno-occlusive function under such conditions will overestimate the degree of suspected corporeal structural disease.

An animal model using the spinal rat was characterized. Electrical stimulation of the dorsal nerve of the penis elicited reflex tonic erections of the penile body and reflex bulbospongiosus muscle activity, flips and ejaculations. The tonic erections of the penile body are independent from contractions of the bulbospongiosus muscle and appear to be the result of a neurovascular process. Our observations suggest that reflex bulbospongiosus muscle activity, flips and ejaculations are a single complex reflex response, which we define as reflex ejaculatory response. Two parameters predicted the occurrence and type of reflex response. The visualization of bulbospongiosus muscle activity during surgical isolation of the dorsal nerve of the penis was sufficient to anticipate the elicitability of reflex ejaculatory responses. The latter, together with a systemic systolic pressure > or = 73 mmHg., warranted the elicitability of reflex tonic erections. The similarities found in the physiology of rat tonic penile body erections and of human erections make this model promising for further elucidation of sexual function. Moreover, the present model may prove useful for the investigation of neurogenic erectile dysfunction, and of neurogenic ejaculatory disorders.

During impotence evaluations a positive intracavernous injection test has been presumed to signify normal erectile hemodynamics. This premise was tested by obtaining hemodynamic data in 80 patients 17 to 65 years old with positive injection tests: patients achieved maximal circumference responses and equilibrium intracavernous pressures of 80 mmHg or more (range 80 to 136) sustained for 30 minutes or longer. Corporeal veno-occlusive testing revealed that flow-to-maintain (0.5 to 3 ml. per minute) and pressure decay (0 to 47 mmHg) values as well as pharmaco-cavernosography findings (absent or minimal contrast medium in venous structures in 92% of the cases) were all consistent with low outflow erection states. Arterial testing revealed right and/or left cavernous systolic arterial blood pressures always at 80 mmHg or more, consistent with a prerequisite cavernous artery pressure value for a positive injection test. Systemic-cavernous systolic arterial blood pressure gradients were 0 to 24 mmHg, 25 to 34 mmHg and 35 mmHg or more in 47 (59%), 18 (22%) and 15 (19%) patients, respectively. Large systemic-cavernous pressure gradients suggested the presence of arterial occlusive disease. In 8 patients with positive injection tests and gradients of 35 mmHg or more pharmaco-arteriography revealed hemodynamically significant arterial occlusions. In conclusion, hemodynamic data in selected patients with positive injection tests revealed low outflow erection states, threshold cavernous artery pressures and disparities in systemic-cavernous systolic pressure gradients that suggested arterial disease in 19% of the cases. The erectile response in a positive test is equal to or greater than a threshold response, not always the maximum response as determined by the systemic blood pressure. A positive intracavernous injection test did not necessarily signify normal erectile hemodynamics.

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