Cavernosal Oxygenation

This is the concept that the penis is a large vein in the flaccid state and a large artery in the erect state. In the flaccid state, the pO2 is approximately 35–40 mmHg. It has been postulated that this results in upregulation of fibrogenic cytokines including TGF-beta. TGF-Beta results in collagen production which may eventually lead to fibrosis and venous leak. During erection the penis is oxygenated with pO2 rising to 75–100 mmHg. In vitro evidence demonstrates that oxygenation upregulates the production of endogenous prostanoids as well as cyclic AMP. Moreland et al. have shown in a series of in vitro experiments that the expo-sure of cultured corporal cavernosal smooth muscle cells that low oxygen levels suppress his PGE1 and cAMP production. Upon returning oxygen environment to normoxia, levels of both normalized. In a further series of experiments, the same authors showed that in the in vitro setting that prostanoids inhibit TGF-beta activity and thus reduce collagen production. Therefore, in a healthy male there is a balance between the flaccid and erect states and as long as men obtaining erections with some degree of regularity, erectile tissue health is preserved. However, after radical prostatectomy in a state of unantagonized flaccidity everything is shifted in favor of fibrogenic cytokine production leading to structural changes and venous leak development. Generic viagra Australia

In a recent study, Mueller et al. demonstrated the potential benefit to hyperbaric oxygen therapy (HBOT) in the cavernous nerve injury model. Animals with bilateral nerve crush injury were divided into the treatment with room air within a hyperbaric chamber versus hyperbaric O2 (3 atm) for 90 min. Animals were treated for a period of 10 days consecutively and at 28 days after bilateral nerve crush, animals underwent functional assessment. Using intracavernosal pressure/mean arterial pressure (ICP/MAP) ratios the animals treated with HBOT had an ICP/MAP ratio of 31%. This com-pared with ICP/MAP ratio of 55% in animals exposed to 10 days of HBOT (p < 0.005). This is not to suggest that patients after prostatectomy be encouraged to enter a decompression chamber for HBOT. However, I do believe that these data support the concept that cavernosal oxygenation is critical to the recovery of erectile func-tion. In unpublished data, emanating from Pfizer Central labs in the UK, a canine model was used to explore the impact of hypoxic conditions on erectile function. In the anesthetized, ventilated dog with the cavernous nerve exposed, cavernous nerve stimulation resulted in progressively poorer ICP/MAP ratios as the FiO2 was dropped from 21% to 18%. In a second series of experiments, the pretreatment of the animals with sildenafil citrate resulted in the preservation of erectile response following cavernous nerve stimulation even under profoundly hypoxic conditions. This suggests that sildenafil at least and perhaps PDE5 inhibitors in general are capable of preserving erectile tissue relaxation profiles even under hypoxic conditions.