It is important to be clear on this point in order to further the discussion about pumping vs. clamping, so I will discuss this a bit more.
I never said that negative pressure outside the penis will increase pressure inside the penis. I was discussing pressure differential between inside and outside. It is the differential that determines how much stress is on the tunica. If you have 1000 psi inside but 1001 psi outside the penis, then the penis is collapsed and you have no tunica stretching, despite the high internal pressure.
Thank you. We are in agreement. Though others dispute this. To make sure that everyone else understands, we are talking about making the pressure in a pumping tube positive not negative. This does not necessarily apply to clamping where the areas away from the clamp will distend.
Yes, and I hope now you see that it is true if we are discussing the pressure differential = P inside minus P outside.
So if you have 200mm inside and then you increase your cylinder pressure to 150mm above atmospheric outside, then you have 50 mm Hg differential. The differential is reduced from the original 200, so you have less force from inside stretching the tunica.
Thank you again. We are in agreement. However the degree of the pressure equalization depends upon the compliance of the vessel we’re sucking on. I can guaranty that at peak erection, the cavernosa pressure dose not become 50 mm Hg if a -150 mm Hg force is applied with a pump..
You are right. For your balloon model, which works for this example, positive pressure outside the balloon increases the pressure inside, but decreases, or fails to change, the pressure differential. The rigidity of the balloon wall will determine how much the pressure outside effects the pressure inside.
Thank you again. We are in agreement.
I think I know what you are getting at. Let’s look at a condom filled with water and a knot in the end.
There is a pressure on the water. Since there is no external source of pressure or flow, the pressure inside is a function of the elasticity of the condom wall, and the air pressure pushing on the condom wall.
If you put this water balloon in a vacuum cylinder, the pressure inside is still P(elasticity) + P(air pressure). Air pressure decreased so pressure inside decreased!
This example is different than the one where there is an external hose or pump attached. We were envisioning different models, so we came to different conclusions.
And I agree totally with this.
If you imagine the model of the tank with the hose and the booster pump (analgous, I hope, to the erect penis with ICM contracting to maintain pressure), then I look at it this way:
The pump maintains a constant pressure. Let”s say in the case of the erect penis it is 200 mm Hg.
Now there is one extra factor in the pressure inside the penis compared to the water balloon above.
Pressure(CC’s)= Pressure (wall elasticity) + Pressure (air pressure) + Pressure (Pump pressure).
Now you put the penis in a cylinder and pull a vacuum. The air pressure part of the equation goes down, but the pressure in the penis probably doesn’t because the pump (ICM contraction) is maintaining pressure.
However, the differential between inside and outside is now greater, because P(inside) is the same, but P (outside) is less.
Again, it is the differential that tells us that the force on the tunica has increased.
We may disagree whether a linear peristaltic pump or a mesh should be used to simulate the system, however I agree with you here.
The extent of the wall tension and response to drawing a negative pressure over the penis will definitely be controlled by the wall elasticity (or distensibility or compliance).
To complete my understanding and application of your system, I envision peak erection (because this is a quasi-stable situation). At this point the tunica is stiff. However the applied negative pressure can more than likely affect a volume-induced tension to cause connective tissue remodeling and increased girth. So even at this very stiff point, I can envision enough distortion to make growth possible
I think we are very close to a meeting of the minds.