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81 Cards in this Set

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  • Back
Power is
the rate energy is transferred. describes how fast work is being done

Watts=Joules/sec
Work is
the amount of energy that is transferred, integrates total power used to complete job over time

Work = avg power x total time

Joules= Joules/ sec x seconds
Energy
has multiple physical forms such as
potential
kinetic
heat
radiation

units vary on which type of energy used
conservation of energy
fundamental law stating that energy is never lost, only converted to another form
potential energy is
energy that is stored and can be converted to another form of energy
kinetic energy is
energy in motion and is proportional to the velocity squared of the movement
pressure is
the measure of force per unit of area

two categories:
Static pressure (potential energy)
Dynamic pressure (kinetic energy)
flow (volumetric) is
the volume of fluid per time that moves past a point

liters/min
meters cubed/sec
resistance is
the ratio of pressure drop across a flow path per volumetric flow

measure of the impediment which is overcome for flow to occur
capacitance is
the measure of the ability to hold a change in volume per change in time

change in V / change in t
compliance is
the ratio of the change in volume to a change in pressure

dV/dP
Velocity is
the speed that a fluid moves in a specific direction

units of distance/time

m/sec cm/sec
viscosity (fluid) is
the ratio of shear stress to the shear rate of a fluid

measure of the resistance of a fluid to flow due to the attraction of molecules
In hemodynamics the driving force that propels blood is a
change in energy

it travels from areas of high energy to those of low energy
when considering the law of conservation energy can be divided into two categories of
potential and kinetic energy
The law of conservation makes it so that there is only a conversion back and forth between
kinetic and potential energies
the pressure that represents the force exerted on the vessel walls represents
potential energy
the force in the direction of flow represents .... which is related to the velocity of the blood
kinetic energy
hydrostatic pressure is
potential energy related to the weight of a column of fluid above a reference point secondary to gravity
the equation for hydrostatic pressure is
ro x g x h
in the hydrostatic pressure equation h means
the height of the column
in the hydrostatic pressure equation ro means
density
in the hydrostatic pressure equation g means
gravity
hydrostatic pressure is proportional to the
height of the column, and density of the material
clinically hydrostatic pressure is related to the ___ and ___ of the patient
height, position
what is the hydrostatic pressure in the body?
2mmHg/inch
In volumetric flow Q means
volumetric flow
in fluid dynamics v is
velocity
high flow does/ doesn't correlate to a high velocity
doesn't
High compliance infers that there is a large increase in ___ with small change in ___
volume, pressure
fluid viscosity is defined as
the ratio of the shear stress to the shear rate

a measure of the resistance to flow offered by a fluid / molecule stickiness
fluid viscosity is ___ dependent
heat
resistance to flow is ___ to the viscosity of the fluid
proportional
for the same radius and the same volumetric flow, if the length increases the resistance ____
increases
resistance is ____ to length
proportional
resistance is ____ to 1/radius
proportional
for the same length, if the radius increases the resistance ___
decreases
which has a greater impact on resistance? length or radius
radius
resistance is ____ to 1/radius^4
proportional
a higher viscosity results in a ____ resistance to flow
higher
what is the resistance equation
R = (8 x length x viscosity) / (pi x radius^4)
for the same velocity a larger CSA ____ volumetric flow
increases
Q is ____ to area
proportional
area is equated as
radius squared
for the same CSA a higher average velocity ____ the volumetric flow
increases
Q is ____ mean spatial velocity
proportional
the contiunity equation states that
flow through one region must equal all the other flow through any other reigion in the flow system
what is the continuity equation
Q = mean spatial velocity x area
a v with a line over it represents
mean spatial velocity
change in P (pressure) is ____ to R (resistance)
proportional
the smaller radius of pipeline B results in a ____ pressure gradient for hte same volumetric lower as pipeline A
higher
change in pressure is ____ to Q
proportional
what is a Newtonian fluid
the viscosity of the fluid only changes with temp
is blood a newtonian fluid
no
What assumptions are made to us poiseuille's law
flow conduit is a rigid cylindrical tube
flow is stead, stable, laminar flow
fluid is newtonian
when is poiseuille's law applicable?
when the hemodynamic state is such that error caused by incorrect assumptions is small enough that the law is good enough to predict behavior
Bernoulli's equation says that
for a closed loop system, all the energy at one point must equal all the energy at another point
to use the simplified Bernoulli's equation we need to assume that
blood is flowing through a rigid tube
blood is a non-viscous fluid
no friction surface occurs
blood is an incompressible homogenous fluid
an blood is in laminar flow
steady flow is
constant volumetric flow
pulsatile flow is
fluid which moves in a well behaved manner and uniform direction

will move in concentric rings not crossing boundaries
plug flow is
a velocity profile that is relatively consistent across the vessel
parabolic flow is
a laminar flow profile which mimics a parabola
normal arterial blood flow in a straight, undiseased segment
disturbed flow
any deviation from laminar flow
turbulent flow is
when fluid does not move in a well behaved manner

chaotic or random flow
acceleration is
change of velocity over time

positive
entrance effect
change in velocity profile which happens when entering a vessel of reduced diameter
exit effect
change in velocity profile which results when exiting from a vessel of smaller diameter

the inertial energy is dissipated by turbulent flow
Raynolds number is
a dimensionless index that indicates the occurrence of turbulent flow
the higher the reynolds number the ____ the likelihood of turbulence occuring
greater
reynolds number is a ratio between the ____ forces and the ____ forces
inertial, viscous
What is reynolds ratio
R = intertial forces / viscous forces
What is reynolds ratio equation
R = (ro x d x v) / (nu)
reynolds number when it is _______ usually results in turbulence
>2000
Explain the normal pressure waveform in the aorta
a rapid systolic upstroke followed by a gradual decrease to the dicrotic (compliance) notch, followed by the gradual decline in pressure throughout diastole
atheroscelrotic arteries will / will not have a dicrotic notch?
will not
capacitance allows energy to be stored in the walls of the aorta to provide
energy to propel blood during diastole
when pressure is applied to an elastic vessel wall, it stretches in a
radial direction, causing an overall increase in CSA over the length of the vessel
compliant vessels cause a fallacy in poiseuille's law assumption because
the compliant vessels create a much faster increase in volume with respect to pressure than the law predicts, causing a non linear relationship change between pressure and volume
how much blood is held in the venous system at rest?
65%
what allows for the venous system to act as a reservoir
it's capacitance
where does blood also reservoir at rest?
skin and liver