Diastolic blood pressure

[Asysin2leads]

Hey all, I'm writing a research paper on diastolic blood pressure in relation to fluid resuscitation, and I'm trying to nail down exactly what factors determine diastolic pressure. From what I've read, diastolic blood pressure is dependent directly on the Law of Laplace. In other words, Wall Tension = pressure x radius/ (2 x Wall Thickness). How could I relate this to the amount of volume circulating in the systemic vasculature?

Edited November 13, 2011 by Asysin2leads

[DwayneEMTP]

Ummm....

Diastolic is the bottom number...I'm pretty sure of that...

You're welcome.. :-)

Dwayne

[WhiskeyTangoFoxtrot]

Ummm...

Less volume equals less pressure X Radius / 2X wall thickness...

Pressure = force / area. I can't remember how to calculate force of a fluid(CHBARE might be able to tell you) but essentially if the area, in this case the walls of the arteries, remains the same, a decrease in volume will decrease the force it exerts on the walls of the artery.

This is an oversimplification of course because when you start calculating in compensation mechanisms where the artery constricts (Alpha 1) thus decreasing the area and the heart pumps harder (Beta 1,Inotropic), thus increasing the force of a smaller volume you can maintain the same pessure with less volume.

I hope this helps a little...

[DwayneEMTP]

Yeah WTF, that's what I meant...

Just sayin'..

Dwayne

[Asysin2leads]

Basically I just want to say that diastolic blood pressure is directly dependent on volume circulating and need some smart soundin' stuff to reference to prove I'm not full of it. Any ideas?

[EMS1700]

Cut and paste Whiskey's post...pretty smart soundin' to me

[systemet]

A few ideas:

* Take a look at a good physiology textbook. Ganong's "Review of Medical Physiology", Vander, Guyton, Boron & Boulpaep -- one of the texts aimed at MD students, not paramedics or RNs. Look through the CV system areas.

* Check this website, it's awesome for a whole bunch of stuff. Here's a couple of particularly relevant pages:

http://www.cvphysiology.com/Blood%20Pressure/BP006.htm

http://www.cvphysiology.com/Blood%20Pressure/BP022.htm

http://www.cvphysiology.com/Blood%20Pressure/BP019.htm

* Think about the biophysics. Consider CO = HR * SV; BP = CO * PVR = HR * SV * PVR = HR * (LVEDV-LVESV) * PVR, and think about the Frank Starling mechanism. Think about the effect that contractility has on this, consider that venous return and central venous pressure / RAP, are surrogates for preload in a healthy heart.

* I think you end up with major determinants being cardiac output, volume and PVR. All of these are affected by multiple factors and aren't completely independent. If you have no volume, you have no preload, no SV, and no CO. If you have no CO, you have no blood pressure.

* Laplace relates to both cardiac contraction, i.e. an overfilled ventricle has a larger radius, and requires the generation of a greater tension to produce the same pressure - this is the reason why nitroglycerin and preload reduction concerve MvO2 in MI, and to vascular function - if we have high PVR from atherosclerotic disease BP will go up. [*This also explains positive feedback in TAAs / AAAs, as the aneurysm dilates, the tension on the wall increases]

* Take a look at vascular function curves here:

http://www.cvphysiology.com/Cardiac%20Function/CF027.htm

I realise this is a lot of information, but if you can look through it, it will really help you understand the complex relationships between the different factors.

[WhiskeyTangoFoxtrot]

translation, we are happy to give you some ideas and point you in the right direction, but we are not going to write your paper for you. :0P

BTW Dwayne, your reply left coffee on my computer. LMAO!

Edited November 14, 2011 by WhiskeyTangoFoxtrot

[Asysin2leads]

Believe me, I wouldn't trust anyone to write a paper for me except yours truly. That would be like Gordon Ramsay asking for a fry cook to whip him up something and claim its his own.

Anyway, I was approaching this from a physics angle. I was trying to relate volume to circumferential stress in a thin walled system using a nifty equation, but upon further review I realized the circumferential stress would be different than the internal pressure of a system and that I was probably making things too complicated. I did learn that circumferential stress is the cause of thickening of the arteries in hypertension, though. We learn something knew everyday.

Edited November 14, 2011 by Asysin2leads

[basejump]

Well I could have copied and pasted that lol.....Also google starlings law and disastolic pressures. You can use google and scholar.google.com depending on how sciency your feeling. I'd love to reply more on this but im out the door for my shift. Cheers, talk soon.