Arterial Hemodynamics Flashcards
what causes blood to move through the circulatory system?
movement of any fluid requires a pathway AND a pressure/energy differential
what determines the amount of flow
energy difference and resistance
blood moves from ____ to _____
high pressure
low energy pressure
potential (pressure) energy
ejection of blood from th heart into the arteries
kinetic (motion) energy
movement of blood as it is ejected from the heart
gravitational energy (hydrostatic pressure)
weight of the column of blood from the heart to the level where the pressure is measured
define plug flow
streamline velocities that are similar from wall to wall along the flow profile. more common at transitions in vessel size and especially at branches and bifurcations.
define parabolic flow
flow that is faster in the center of the vessel (streamline)
what is the Reynolds number for laminar flow
<1500
what is the Reynolds number for turbulent flow
> 2000
resistance is DIRECTLY proportional to
viscosity and length
increased resistance, increased viscosity and length
resistance is INVERSELY proportional to
vessel radius
decreased radius, increased resistance
describe Poiseuille’s law and what is the formula
formula:
Flow=Pressure/Resistance
defines how blood moves through a given vessel segment and the entire system
pulsatile flow, describe early systole
cardiac contraction
aortic valve opens
high velocity ejection of blood
see page 50
pulsatile flow, describe late systole/early diastole
rapid deceleration and aortic valve closes
“dicrotic notch” represents aortic valve closure
see page 50
pulsatile flow, describe late diastole
low flow velocity or no forward flow
depends upon the resistance of the vascular bed
see page 50
describe area/velocity relationship
area and velocity are inversely proportional
decreased area, increased velocity
describe Bernoulli’s principle
Relationship between velocity and pressure
velocity and pressure are inversely proportional
increased velocity, decreased pressure
describe what happens when hematocrit increases
increases viscosity (thickness of blood)
what happens when patient is anemic
decreased viscosity
describes systolic upstroke, and what does it mean when there is a delay
shows where the blood came from
delayed systolic upstroke means stenosis proximal
describe diastolic flow, and how does it relate to resistance
shows where the blood is going
the resistance of the downstream vascular bed
