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Vascular 2 > Module 2 : Arteriole Hemodynamics > Flashcards

Module 2 : Arteriole Hemodynamics Flashcards

1
Q

what are the two conditions for fluid to move from one point to another

A
  • a path for the fluid

- a difference in energy (pressure) level from point to point

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2
Q

3 types of energy contained in moving fluids

A
  • potential (pressure)
  • kinetic
  • gravitational
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3
Q

potential (pressure)

A
  • the primary energy present in blood flow
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4
Q

kinetic energy

A
  • energy of something already in motion
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5
Q

gravitational energy

A
  • hydrostatic pressure
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6
Q

what is the primary pressure source in circulation

A
  • the systolic contraction of the heart creates an energy gradient for blood to flow
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7
Q

what two factors dictate the volume of blood leaving the heart

A
  • blood pressure

- peripheral resistance

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8
Q

stroke volume definition

A
  • amount of blood ejected from the heart during systole
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9
Q

how does the arteriole system change with increased volume

A
  • in respones to the increase volume and pressure arterial walls expand which creates POTENTIAL ENERGY within them called SYSTOLIC PRESSURE
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10
Q

diastole effect on volume and pressure

A
  • blood volume decreased during diastole
  • artery decreases in diameter
  • pressure decreases and blood flows due to its own momentum
  • DIASTOLIC PRESSURE
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11
Q

what is the pressure gradient between left ventricle and right atrium

A
  • 120mmhg / 2-6mmhg
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12
Q

what does Bernoulli principle explain

A
  • maintenance of energy in the movement of the fluid
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13
Q

Bernoulli principle describes relationships between what three things

A
  • area
  • velocity
  • pressure at a stenosis
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14
Q

Bernoulli energy equation

A

total energy = potential E + kinetic E

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15
Q

Bernoulli and three statements on energy

A
  • over relatively STRAIGHT partial segments, balance of kinetic (blood flow) and potential (blood pressure) energy is maintained
  • if artery lumen increases kinetic energy is converted back into pressure (potential energy) when velocity is increase
  • is artery lumen decreases, the potential energy is converted into kinetic energy
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16
Q

Bernoulli increase in kinetic energy leads to what change in velocity

A
  • increase in kinetic energy occur in the systemic circulation where blood flow is high in stenotic lesions and luminal narrowing leads to increase in blood flow velocities and decrease pressure
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17
Q

laminar flow

A
  • aka parabolic
  • normal flow
  • each layer travels at different velocities
  • slowest flow is near the vessel wall
  • fastest flow located at centre of vessel
  • BLOOD MOVES IN CONCENTRIC LAYERS
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18
Q

blunt flow

A
  • aka plug flow
  • uniform flow across the vessel
  • occurs during SYSTOLE in larger vessel
  • also at some arterial branch origins
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19
Q

non laminar flow

A
  • aka disturbed
  • normal and abnormal
  • some conditions laminar flow can be disrupted and once it is altered the velocity profile is not reestablished for
    3CM
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20
Q

flow separation

A
  • occurs when there is sudden WIDENING OF VESSEL
  • fluid layers separate to fill the newly opened area creating MIXED BLOOD FLOW PATTERN
  • this causes FLOW REVERSAL ALONG THE WALL
  • considered NORMAL
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21
Q

transition zone

A
  • area where the lamina reach zero-velocity is refer to as the site of the boundary layer separation
  • seen at carotid bulb and distal to stenosis
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22
Q

flow pattern at bifurcations and branches

A
  • layers become disrupted and will show DISTURBED flow
  • flow patter may differ depending on angle and size of vessel
  • A LARGER ANGLE WILL RESULT IN GREATER FLOW DISTURBANCE
  • small pressure drop at bifurcation
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23
Q

flow patter in curved vessels

A
  • when blood moves around a cure the fluid in the centre moves outward and is replaced by the slower flow located near the arterial wall
  • called a HELICAL FLOW PATTERN
  • FLUIDS FLOW FASTER ON TEH OUTSIDE AND FLOW MAY APPEAR REVERSED ON TEH INSIDE as the fluid fils the inner void from the outward shift
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24
Q

resistance and pressure gradient relationship

A
  • to preserve blood flow through out the body if there is an increase in resistance the pressure gradient must increase
25
Q

abbreviated poiseuilles equation

A

Q = (P1 - P2) / R (resistance)

26
Q

flow (Q)

A
  • the amount of fluid traveling past a point in a given amount of time (L/min)
27
Q

poiseuilles law

A
  • defines the relationship between pressure volume flow and resistance of a fluid flowing through a cylinder tube model
28
Q

poiseuilles equation

A

Q = pi (P1 - P2)r^4 / 8Ln

Q = flow volume
n = viscosity
L = length of vessel 
r = radius
P1 - P2 = pressure gradient
29
Q

viscosity (n)

A
  • resistance to flow of a fluid in motion
  • how thick it is / stickiness
  • frictional forces that occur as molecules of blood move against eachother
  • measured in POISE
  • concentration of RBC (hematocrit) and plasma protein is MOST IMPORTANT FACTOR EFFECTING VISOCISTY
30
Q

length (L)

A
  • due to increase friction a longer tube contains more resistance than a smaller tube
  • RESISTANCE INCREASES AS LENGTH INCREASES
31
Q

radius (r)

A
  • artery radius has THE LARGEST EFFECT on resistance
  • as vessel radius decreases resistance increases to the 4th power
  • in lower extremity this is effected by ecersize and vasodilation radius increases resistance decreases
32
Q

poiseuelles vs Bernoulli

A
  • poiseuille us based in entire long tube so flow speed is less in smaller diameters
  • Bernoulli is based on just the short portion of the vessel (stenosis) so flow speed is increased with smaller diameters
33
Q

what is turbulent flow

A

chaotic flow where fluid is exiting a tight spot and entering an enlarged space

34
Q

how is the fluid moving in turbulent flow

A
  • eddies and whirls

- very disordered

35
Q

what types of vessels does turbulent flow occur

A
  • develops more easily in larger vessels with high flow volumes
36
Q

spectral trace of turbulent flow

A
  • feathered appearance

- spectral broadening

37
Q

what is the Reynolds number

A
  • the number at which turbulence occurs when it is met or exceeded
  • 2000
38
Q

Reynolds number equation

A

Re = average flow x density x tube diameter / viscosity

39
Q

according to the equation what will increase turbulence

A
  • increases flow
  • increasing density
  • increasing tube diameter
  • decreasing velocity
40
Q

why will the velocity increase at a stenosis

A
  • velocity increases because pressure decreases (BERNOUILLI)
41
Q

why will there be turbulence post stenosis

A
  • because of increased velocity and sudden increase to vessel radius (REYNOLDS POISEUILLE)
42
Q

hemodynamic effect of arterial stenosis

A
  • according to bernouille there will be a pressure drop at the entrance to a stenosis because a higher velocity is needed to maintain flow volume
  • at the exit turbulent flow may be seen due to jet entering the wider lumen
  • distal to exit the velocity decreases due to increase lumen size resulting in an increase in pressure
43
Q

how are velocity and pressure related in a stenosis according to Bernoulli

A

they are inversely related

44
Q

energy can be lost within a stenosis due to what three factors

A
  • length of stenosis
  • whether there is tandem stenosis
  • surface contour of plaque
45
Q

7 factors within a stenosis that cause hemodynamic change

A
  • length and diameter of narrowed segment
  • surface roughness
  • surface irregularity and shape of lesion
  • ratio of normal vessel diameter to narrowed segment
  • collateral circualtion
  • pressure gradient
  • peripheral resistance to stenosis
46
Q

spectral tracing proximal to stenosis

A
  • increased pulsatility
  • narrow sharp peak
  • low PSV dues to decreased flow
  • laminar flow
  • THUMPING IN SYSTOLE
47
Q

spectral trace within stenosis

A
  • increased velocities not necessarily isolated to stenotic segment
  • PSV increases until 80% reduction occurs
  • EDV is markedly increased with > 70% stenosis
48
Q

spectral trace distal to stenosis

A
  • flow reversal, flow separations, vortices and eddy currents seen (post stenotic turbulence)
  • maximum flow disturbance is seen within 1cm with visible bruit
  • ## dampened or trades parvus seen distal
49
Q

tandem lesions characteristics

A
  • greater loss of energy and volume
  • first stenosis have greater incoming energy and will usually produce higher velocities than the second stenosis as it will have decreased incoming energy
50
Q

low resistance flow pattern

A
  • constant foward flow in systole and diastole with a diastolic component way above baseline
  • feeding important things like brain
51
Q

high resistance flow pattern

A
  • sharp upstroke with low to absent diastolic flow
  • more pulsatility
  • feeding things that are less important
52
Q

pulsatiility is caused by what and causes what

A
  • due to the pulsatile pumping activity of the heart
  • causes alternating phases of acceleration and deceleration
  • low, moderate, high
53
Q

low pulsatility

A
  • low resistance

- broad systolic peak with forward flow in diastole

54
Q

moderate pulsatility

A
  • tall sharp peak

- little diastolic flow

55
Q

high pulsatility

A
  • high resistance
  • narrow systolic peak
  • flow reversal in early diastole
  • little or absent late diastolic flow
56
Q

pulsatility index equation

A

PI = PSV - EDV (lowest point) / MEAN V

57
Q

resistivity index equation

A

RI = PSV - EDV / PSV

58
Q

systolic / diastolic ratio

A

S/D = PSV / EDV

Vascular 2 (9 decks)

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