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61 Cards in this Set
- Front
- Back
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Hemodynamics
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Study of blood moving through the circulatory system
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Synonym for Flow
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Flow Rate
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Flow is
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the volume of blood moving during a particular time
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Flow answers the question...
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How much?
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Flow is expressed in...
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Liters/minute
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3 forms of matter
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Gas, liquid, solid
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Gas and Liquids are
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Fluids that will conform to the shape of a container
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Example of flow
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streams (change position and possible direction)
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Blood is made up of:
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Plasma, red blood cells (99%), white blood cells, platelets
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Hematocrit
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# of total blood cells
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2 Characteristics of Fluid:
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Density and Viscosity
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Density
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mass per unit volume (g/ml),
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Viscosity
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Resistance of fluid to flow, thickness of a fluid
-measured in poise (kg/m-s) |
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In patients who are anemic, what happens to the viscosity of thier blood?
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Hematocrit reduced, reduced viscositiy with less energy lost.
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Why does blood move?
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Total fluid energy at one location DIFFERS total fluid energy at another location
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Enegy Gradient
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High to Low Pressure
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Forms of energy
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Kinetic
Pressure Gravitational |
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Kinetic Energy
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Moving Objects
Determined by: mass and speed -Heavy objects moving fast have lots of Kinetic energy (ping pong ball vs tennis ball hitting window) |
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Pressure Energy
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-Form of stored or potential energy
-Ability to perform work -force per unit area -Pressure is distributed equally throughout static fluid and exerts force in all directions |
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= Pressure =
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NO FLOW
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Gravatational Energy
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Any elevated object
Form of stored or potential energy Example: SKi downhill |
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Blood flow energy is lost on 3 ways
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Viscous loss
Frictional Loss Inertial loss |
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Viscous Loss
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-
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Frictional Loss
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-converted to heat as cells rub against each other
-blood slides against vessel walls to create heat |
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Inertial Loss
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fluid to resist change in a velocity
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Pressure/Flow Relationships:
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Vessels are elastic, made of collagin and smooth muscle.
Greater Pressure= increased flow |
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Poiseulles Equation
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In relation to steady flow in long straight tubes.
Substitute diameter for radius in flow resistance equation |
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Pousilles Predictions
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Pressure Diff increases as flow rates increases
Diameter increases as Flow rate increases If length increases, flow rate decreases If viscocity increase, flow rate decreases |
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Types of flow:
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Spatial
Laminar |
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Spatial Flow include:
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Plug
Laminar Parabolic Disturbed Turbulent |
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Laminar Flow includes the forms:
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Plug
Parabolic Disturbed |
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circulatory system consists of
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heart, arteries, arterioles, capillaries, venules, and veins, altogether containing about 5 liters (L) of blood
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Inertial Loss occurs to:
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Pulsatile Flow (arterial)
Phasic Flow (venous side) Velocity changes at a stenosis (Narrowing in vessel) |
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Pressure Gradient equation:
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Flow * Resistance
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Pressure Gradient Increases with:
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Increased flow and resistance
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when tube length increases flow...
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increases
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when tube radius increases flow...
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increases
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when viscocity increases flow...
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decreases
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Laminar Flow exists when:
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-Streamlines are aligned
-lines are parallel -layers of blood that travel at individual speed, speeds are not consistent |
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Plug Flow exists when:
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All layers are the same velocity
"unit" -form of laminar |
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Parablic flow
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bullet shaped profile
see this in cardiac initially starts with varying velocities fastest in center |
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Disturbed Flow
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3rd form of laminar
when parallel streamlines are altered particles still move in forward direction |
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Turbulent Flow
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Random and chaotic
different speeds and different directions (class dismissed example) |
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Turbulent Flow converts energy into:
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Sound (murmer)
Vibration (palpating) |
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Bruie
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Audible sound in caratoid artery
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Thrill
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when turbulant flow is being converted into something else
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Some numbers to know
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less than 1500- laminar
more than 2300 turbulent |
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critical reynolds number
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2000 ( approaching turbulent
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Pulsatile Flow
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when blood moves with a variable velocity
aterial circulation excelerates and decelerates with every cardiac contraction |
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Phasic Flow (Respiration/Venous)
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Respiration, not the heart.
found in venous system also moves with variable velocity |
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steady flow
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fluid moves at a constant speed (not normal)
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What plays a role in flow impeadance?
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Resistance
accelaration and decelarion (inertia) Compliance: expand and contract of vessels |
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2 Dominant factors of pulsatile flow:
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Windkessel effect
flow reversal |
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windkessel effect
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volume increases in vessel due to pulse
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Stenosis
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Narrowing in the lumen of a vessel
(plaque example) |
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4 Stenosis Effects
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1-change in flow direction of blood
2-increased velocity within stenosis 3-turbulence downstream from stenosis (PST) poststenoic turbulence 4-pg downstream=lower than pg upstream (high to low) |
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Most severe narrowing=
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velocity increased
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Continuity Rule
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Average flow speed. Needs to be equal but in order for that to occur q2 velocity must increase. (q1=q2=q3)
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Volumetric Flow rate
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Average flow speed within stenosis is 2x that proximal and distal to it.
example highway trafffic from 4 to 2 lanes, cars have to go faster to keep same rate |
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Bernouli Effect
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A drop in pressure with high flow speeds at stenosis.
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Bernouli simplified
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4v2, unless greater than 1 m/s.
cardiac most practical |
