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RVT Review > Chapter 2 > Flashcards

Chapter 2 Flashcards

1
Q

how does the cardiac contraction begin?

A
  1. pressure in the left ventricle rises rapidly
  2. left ventricle pressure exceeds that in the aorta
  3. aortic valve opens; blood is ejected, BP rises
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2
Q

increased heart rate delivers what?

A

an increase in blood volume

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3
Q

what is the heart pump?

A

generates the pressure to move the blood

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4
Q

What does the heart pump result in?

A

in a pressure wave (energy wave) that travels rapidly throughout the system, demonstrating a gradual transformation as it travels distally

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5
Q

what is the inflow arteries?

A 
lt ventricle 
aorta
large arteries 
arterioles 
capillaries
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6
Q

what is the outflow arteries?

A 
capillaries 
venules 
large veins 
vena cava 
rt atrium
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7
Q

what does the pumping action of the heart results in?

A

high volume of blood in arteries to maintain a high pressure gradient between the arteries and veins

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8
Q

what govern that amount of blood that enters the arterial system?

A

cardiac output

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9
Q

What determines the amount of blood that leaves the arterial system?

A

arterial pressure and total peripheral resistance

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10
Q

what does the cardiac contraction do?

A

distends the arteries; which serves as reservoirs to store some blood volume and potential energy supplied to the system

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11
Q

where is the pressure the most greatest?

A

at the heart

decreases as blood moves further away from the heart

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12
Q

movement of any fluid medium between two points requires two things?

A

a. a pathway along which the fluid can flow

b. difference in energy levels (pressure difference)

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13
Q

what does the amount of flow depends upon?

A

energy difference includes losses resulting from fluid movement
any resistance which tends to oppose such movement

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14
Q

how are flow rate and resistance related?

A

inveresly

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15
Q

What is the equation for total energy?

A

sum of pressure (potential), kinetic and gravitational energy

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16
Q

What is pressure (potential) energy?

A

store energy and is the major form of energy for circulation of blood; measured in mmHg

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17
Q

what is kinetic energy?

A

small for circulating blood

expressed in fluid density and velocity measurements

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18
Q

what is gravitational energy?

A

hydrostatic pressure, is equivalent to the weight of the column of blood extending from the heart to level where pressure is measured

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19
Q

what is the HP in the ankle when a patient is standing?

A

100 mmHg

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20
Q

What is the HP in the ankle when a patient is supine?

A

0 mmHg

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21
Q

what is the formula to calculate ankle pressure?

A

ankle P= circulatory P + HP

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22
Q

what is needed to move blood from one point to another?

A

energy gradient

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23
Q

What is the relationship between energy gradient and flow?

A

direct

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24
Q

what is inertia?

A

relates to the tendency of a fluid to resist changes in its velocity
e.g body at rest tends to stay at rest

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25
Q

as the blood moves farther out to the periphery, energy is dissipated as what?

A

heat

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26
Q

how is energy restored?

A

by the pumping action of the heart

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27
Q

what is movement of a fluid is dependent upon what?

A

physical properties of the fluid and what its moving through

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28
Q

what is the formula for resistance?

A

r= 8nL/pie R4

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29
Q

what has the most influence on resistance?

A

a change in vessel diameter

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30
Q

internal friction within a fluid is measured by what?

A

viscosity

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31
Q

what are some friction measured by viscosity?

A

a. energy is lost in a form of heat ( RBCs rubbing against each other)
b. elevated hematocrit= increases in viscosity
severe anemia= decreases in viscosity

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32
Q

what does diminishing vessel size increase?

A

increases frictional forces and heat energy losses

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33
Q

what is the relationship between velocity and viscosity?

A

inversely

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34
Q

what is laminar flow?

A

layers of fluid particles moving against one another

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35
Q

where is the fastest moving particles?

A

in the center

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36
Q

where is stationary flow at?

A

remains at the walls

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37
Q

what is laminar flow considered?

A

stable flow

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38
Q

what is plug flow?

A

blunted flow
is likely seen at vessel origin
]

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39
Q

what is parabolic flow?

A

profile of laminar flow usually seen downstream

>

40
Q

what is viscous energy losses due to?

A

increased friction between molecules and layers which causes energy losses

41
Q

what is inertial losses due to?

A

occur with deviations form laminar flow due to changes in direction and/or velocity

42
Q

what are some characteristics of inertial losses?

A
  • the parabolic flow profile become flattened
  • flow moves in a disorganized fashion
  • this type of energy loss occurs at the exit of a stenosis
43
Q

what is poiseuilles equation?

A

flow=pressure/resistance

44
Q

which equation helps answer the question of how much fluid moves through a vessel?

A

poiseuilles

45
Q

what is ohms law?

A

current=voltage/resistance I=V or E/R

46
Q

what are other two ways to write poiseullies equation?

A

Q= (P) pie R4/8nL
Q= (p1-p2)pieR4/8nL
Q= AxV
P1-P2- pressures at proximal/distal ends

47
Q

what is the relationship between radius and volume flow?

A

directly

48
Q

which principle explains the relationship b/w velocity and pressure?

A

bernoulli

49
Q

if there is a change to one of the total energy what happens?

A

the other make up for the difference in order to maintain the original total fluid energy amount

50
Q

what is the relationship between velocity and pressure?

A

inversely

51
Q

why do pressure gradients (flow separations) occur?

A

geometry change with or without intra-luminal disease and b/c of curves
e.g bulb
tortuous vessel

52
Q

where flow separations result in?

A

in regions with stagnant or little movement

e.g bypass graft anastomosis site, or valve cusp site

53
Q

where does steady flow originate from?

A

from a steady driving pressure

54
Q

what are some characteristics of steady flow?

A

a. easy to deal with b/c behavior is more predictable

b. in a rigid tube, energy losses are mainly viscous can be described by poseuilles equation

55
Q

what is pulsatile flow?

A

changes both the driving pressure conditions as well as the response of the system

56
Q

what are some characteristics of systole?

A

forward flow throughout the periphery

fluid acceleration

57
Q

what are some characteristics of late systole/ early diastole?

A

temporary flow reversal, due to a phase shifted negative pressure gradient and peripheral resistance, causing reflection of the wave proximally

58
Q

what are some characteristics of late diastole?

A

flow is forward again, as reflective wave hits the proximal resistance of the next oncoming wave, and reverses

59
Q

what is low resistance flow?

A

flow of a continuous steady nature feeding a dilated vascular bed

60
Q

what vessels are low resistive?

A

ICA, verts, renal, celiac, splenic, hepatic, non fasting SMA

61
Q

what is high resistance flow?

A

flow of a pulsatile nature. between incident pulses, hydraulic reflections travel back up the vessel fro the periphery producing flow reversals in the vascular compartment

62
Q

what vessels are high resistive?

A

ECA, subclavian, aorta, iliac, extremity arteries, fasting SMA

63
Q

what can happen to the reversal component of a high resistant signal distal to a stenosis?

A

it may disappear due to decreased peripheral resistance, secondary to ischemia

64
Q

what does the doppler flow distal to a stenosis look like?

A

lower resistant
more rounded in appearance and is weaker in strength
tardus parvus

65
Q

what can happen to a high resistive waveform as it approaches a stenosis?

A

it can go from tiphasic to monophasic

66
Q

what does the doppler flow proximal to a stenosis look like?

A

higher resistant

could have no diastole or minimal diastole

67
Q

what happens with vasoconstriction?

A

pulsatile changes in the medium/small sized arteries of the limbs are increased. the pulsatility changes are usually decreased in the minute arteries

68
Q

what waveform is normally seen with vasoconstriction?

A

high resistive

69
Q

what waveform is normally seen with vasodilation?

A

low resistive

70
Q

what happens with vasodilation?

A

pulsatile changes in the medium/small sized arteries of the limbs are decreased. while in the minute arteries are increased

71
Q

as the inflow pressure falls as a result of stenosis, what is the peripheries natural response? vasodilate or vasocontrict

A

vasodilate

72
Q

why can total blood flow be fairly normal due to collaterals?

A

development of a collateral network and a compensatory decrease in peripheral resistance

73
Q

what changes occur with collaterals?

A

increased volume flow
reversed flow direction
increased velocity
waveform pulsatility changes

74
Q

T/F location of collaterals help provide tentative location of the obstruction

A

true

75
Q

what effect does exercise have?

A

exercise should induce peripheral vasodilation which lower the distal peripheral resistance, increasing blood flow

76
Q

what is the best single vasodilator of resistance to vessels?

A

exercise

77
Q

what is augoregulation?

A

ability of most vascular beds to maintain constant level of blood flow over a wide range of perfusion pressures

78
Q

what changes occur when BP rises?

A

constriction of vessels

vasoconstriction

79
Q

what changes occur when BP falls?

A

dilation of vessels

vasodilation

80
Q

does exercise increase or decrease reflection?

A

decrease

81
Q

flow to a cool extremity will have what kind of signals?

A

pulsatile signals

vasoconstriction

82
Q

flow to a warm extremity will have what kind of signals?

A

continuous, steady signals

vasodilation

83
Q

T/F pulsatiliy changes do differentiate well between occusion and severe stenosis?

A

false

84
Q

T/f waveforms may not be altered with good colateralization

A

true

85
Q

T/F distal effects of obstructive disease may only be detectable following stress

A

true

86
Q

T/F a hemodynamically significant stenosis does not cause a notable reduction in volume flow and pressure

A

false

87
Q

what happens when cross sectional area reduction of 75%?

A

diameter reduction by 50%

88
Q

where are lower frequencies distributed?

A

at walls, boundary layer

89
Q

where are high frequencies distributed?

A

centerstream

90
Q

what factors does effects of flow abnormality produced by a stenosis depend on?

A

a. length, diameter, shape, and degree of narrowing
b. multiple obstructions in the same vessel, resistance to flow is additive. it results in a higher resistance than in each individual narrowing
c. obstructions in different vessels that are parallel, resistance is lower
d. pressure gradient; peripheral resistance beyond stenosis

91
Q

what happens pre stenosis?

A

flow frequencies are usually dampened, with or without disturbance

92
Q

what happens at stenosis?

A

increase in doppler shift frequencies, resulting in spectral broadening and elevated velocities

93
Q

why do flow distrubances occur?

A

occurs due to interrupted flow stability with high velocities and eddy currents

94
Q

what happens post stenosis?

A

flow reversals, flow separations, vortices/eddy currents occur near edge of flow pattern
spectral broadening
energy expended as heat as eddys and vortices work against blood viscosity

95
Q

what are abnormal jet?

A

elevated velocities

RVT Review (30 decks)

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