Compliance and aortic systolic/diastolic pressure

[IntelInside]

Why is it that aortic diastolic pressure decreases when compliance decreases?

If I am looking at a V vs P graph with compliance graphed on it and we were to compare the 3 aortas of different compliances. The one with the lowest compliance would have the greatest P at that given V. So why is it that aortic diastolic pressure decreases with a decrease in compliance.

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[Charles_Carmichael]

Why is it that aortic diastolic pressure decreases when compliance decreases?

If I am looking at a V vs P graph with compliance graphed on it and we were to compare the 3 aortas of different compliances. The one with the lowest compliance would have the greatest P at that given V. So why is it that aortic diastolic pressure decreases with a decrease in compliance.

In normal arteries, when blood is pumped from the heart, the arteries expand (increase in diameter) due to elasticity and "store" some blood and during diastole, the recoil of the arteries pushes the stored blood through the circulatory tree to give the diastolic pressure. When the compliance decreases, this capacity to "store" blood decreases and thus, the diastolic pressure decreases also.

At least, that's how I learned it.

 

[Bernoull]

In normal arteries, when blood is pumped from the heart, the arteries expand (increase in diameter) due to elasticity and "store" some blood and during diastole, the recoil of the arteries pushes the stored blood through the circulatory tree to give the diastolic pressure. When the compliance decreases, this capacity to "store" blood decreases and thus, the diastolic pressure decreases also.

At least, that's how I learned it.

+1

Vessel compliance basically modulates bp to keep it within a relatively narrow range, this is key given that the heart is an intermittent pump. Without compliance bp will peak and crash with every beat (think of quickly opening a faucet then shutting it repeatedly). Diseased aorta are less elastic/compliant therefore they can't modulate bp quite as well, hence systolic pressure increases and diastolic pressure decreases (greater swings in bp essentially)...

 

[da8s0859q]

+1

Vessel compliance basically modulates bp to keep it within a relatively narrow range, this is key given that the heart is an intermittent pump. Without compliance bp will peak and crash with every beat (think of quickly opening a faucet then shutting it repeatedly). Diseased aorta are less elastic/compliant therefore they can't modulate bp quite as well, hence systolic pressure increases and diastolic pressure decreases (greater swings in bp essentially)...

+1 to this +1.

OP, the other way you can think about it is not just a storage of a little bit of blood due to compliance / elasticity, but the release of a little bit of extra pumping pressure during diastole.

Dunno if you've already covered it, but think about the Windkessel effect (here) and how it's intended to smooth out BP and perfusion to organs. Short version:

1. Systole -> high-pressure cardiac output -> expansion of large/medium arterial walls -> storage of energy (and a little blood) in elastic arteries.

2. Diastole -> lower pressures -> "snapping" back into place of large/medium arterial walls -> release of stored energy/blood, adding a bit to blood pressure both ways.

So if compliance goes down, arteries can't expand as much, so systolic pressure goes up. And if they're not compliant, than diastolic pressure loses the impact of the "stored" blood like Kaushik said -- and whatever added pressure there might have been by the Windkessel effect.