Hemodynamics Flashcards
What are the two kinds of flow?
forward and reverse flow
What is hemodynamics?
literally “blood movement”
the study of blood FLOW or the circulation
Forward flow is _____the line, reverse flow is ______the line
Above
Below
What is circulation?
flow of blood through a closed system
What makes up the arterial system?
multibranched elastic conduit that carries blood away from the heart
What is energy?
blood flow is in motion
ability to do work
conservation of energy - energy is never lost only converts to another form
What is potential energy?
resting energy (static)
What is kinetic energy?
motion energy (dynamic)
What is power?
concentration of force per unit area
force behind fluid flow
What is total energy?
kinetic + static
the pressure exerted by a fluid due to its weight or force per unit area is called?
hydrostatic pressure
What is the energy or pressure gradient?
pressure difference in order for blood to move
flow is from high to low pressure
gradient = difference
Pressure has to build in the left ventricle before it can eject blood out of the aortic valve into the aorta, true or false?
true
What is stroke volume?
the AMOUNT (volume) of blood ejected
equal to the DIFFERENCE between end diastolic volume and end systolic volume
pressure is necessary to….
maintain flow
the greater the pressure gradient, the ______the flow rate
greater
What is the energy gradient?
determines flow
what causes loss in flow?
friction
resistance
What are some things that can cause friction/resistance?
clot
thrombus
tumor
The greater the resistance the ______the flow
lower
what is the sign for the pressure gradient?
triangle ^P
What is viscosity?
THICKNESS — resistance to flow
What are the different types of flow?
laminar flow - normal - layers with the highest velocities in the center stream
parabolic - bullet shape
plug - SAME velocity
these are all NORMAL
What is Poiseuille’s Law?
in an ARTIFICIAL SYSTEM how the flow changes
the smaller the more pressure needed
the thicker the slower the flow
how much pressure is needed if you change pressure, length or viscosity
What are the three primary factors that determine the resistance to blood flow within a single vessel
finish slide 28
In Poiseuille’s Law, what are the direct and indirect relationships?
Direct:
pressure increases, flow rate increases
diameter increases, flow rate increases
Indirect:
length increased, flow rate decreased
viscosity increases, flow rate decreases
resistance increases, flow rate decreases
What accounts for about half of the resistance in systemic circulation?
resistance of the ARTERIOLES
What does Bernoulli’s principal say about pressure?
velocity and pressure are inversely related
high velocity = low pressure
low velicity = high pressure
relationship in a stenosis high velocity with low pressure
look at slide 34…what is the diagnosis?
spectral broading….LRA stenosis
Slide 35, recognize the difference flow patterns
peripheral resistance
low resistance
high resistance
What happens to velocity and pressure when you have a stenotic vessel?
velocity increase
pressure decreases
What three things might you see on US if you have a stenotic vessel?
reduction in volume flow
bruits
spectral broadening
slide 37 for picture
What are the different types of laminar flow?
parabolic
disturbed - flow breaks down
plug - uniform speed or velocity
What are the two kinds of turbulent flow
chaotic
Eddies - flow is kind of like a tornado (ex: pseudoaneryusm)
What is Reynolds number?
a number used to show turbulence
if the number is above 2000, flow is turbulent
increase in flow speed increases _________number, increase in vessel radius _______ reynolds number
reynolds number
increases
What is pulsatile flow?
non steady flow with acceleration and deceleration over the cardiac cycle
What is the continuity rule?
flow rate must be constant proximal, at and distal to a stenosis
flow speed ______at a stenosis and _______can occur distally
increases
turbulence
What is an occlusion?
blocked vessel - no flow
what is bruits?
sound produced by turbulence - indicates a change in flow
What is triphasic - high pulsatility?
sharp upstroke in systole - has three points
flow reversal - resistance
forward flow
what is biphasic flow?
moderate pulsatility - goes up and down
What is monophasic flow?
low pulsatility
broad systolic peaks
