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Flashcards in Hemodynamics Deck (18)
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1

What is the equation for simple blood flow?

change in pressure/Resistance

2

What is Poiseuille's law

check

3

what is a way of defining resistance?

Change in pressure/ flow

4

What is the rearrangement of Poiseuille's law when resistance is substituted as change in pressure/flow

check

5

What do flow and resistance depend on

Change in pressure, length of vessel, viscosity of fluid but huge dependence on radius of vessel

6

What are 5 assumptions that Ps law makes

1. The blood flow is laminar
2.The blood flow is consistent and not pulsatile
3. The blood vessel is rigid, unbranched and with a consistent radius
4.The viscosity of the fluid must be consistent
5. The fluid must be incompressible

7

What happens if tissue pressure drops

causes the collapse of some vessels - at the critical closing pressure

8

What is transmural pressure? - Laplace's law

The change in pressure between inside the vessel and just outside the vessel
P=tension/radius - tension = (P.internalradius)/wall width

9

What is an aneurysm

A swelling of blood - internal radius increases - wall width decreases so tension decreases (Laplace's law) - Is the vessel can no longer produce the level of tension required a blowout (burst) may occur - positive feedback mechanism - increased tension leads to more vessel damage....

10

What is compliance

The change in volume/ change in pressure

11

What is a compliant vessel

One that can produce a large change in volume for a small change in pressure

12

Which are more compliant: veins or arteries

Veins - store more blood - act as capacitance vessels - post mortem blood tends to pool in veins

13

How is the blood flow in the aorta described

Pulsatile and discontinuous - Periods of time where there is zero flow followed by peaks and troughs

14

Where else is pulsatile flow seen

Renal artery - but it never hits zero
seen in arteries supplying major organs

15

Why is discontinuous/ pulsatile flow seen in arteries supplying the main organs

Mainly due to the elastic aorta region - Elastic tissue stretches and stores energy - once the pressure begins to drop the tissue recoils. Energy in the tissue has to go somewhere so provides an extra pumping action for the movement of blood

16

What is the equation for reynolds number

check

17

What R number dictates laminar flow of blood

<2000

18

What R number dictates turbulent flow of blood

>3000