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Vascular Boards > Chapter 2: Physiology and Hemodynamics > Flashcards

Chapter 2: Physiology and Hemodynamics Flashcards

1
Q

each heart beat pumps about _____mLs of blood into the aorta

A

70

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2
Q

Cardiac Contraction stages:

A 
pressure in lt ventricle rises
lt ventricle pressure exceeds aortic pressure
aortic valve opens
blood is ejected
BP rises
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3
Q

Increased heart rate delivers _____ blood volume

A

increased

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4
Q

The heart pump:

A

generates pressure to move the blood

results in pressure wave (energy wave) that travels through the system

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5
Q

blood flow through system

A 
lt ventricle
aorta
large arteries
arterioles
capillaries
venules
large veins
vena cava
rt atrium
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6
Q

the pumping action of the heart results in

A

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

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7
Q

cardiac output governs

A

the amount of blood that enters the arterial system

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8
Q

what determines the amount of blood that leaves the arterial system

A

arterial pressure and total peripheral resistance

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9
Q

pressure is greatest at

A

the heart
gradually decreases as blood moves further away
this pressure difference is necessary to maintain blood flood

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10
Q

movement of any fluid between two points requires two things:

A

a pathway along which the fluid can move

difference in energy levels (pressure difference/energy gradient)

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11
Q

the amount of flow depends on

A

energy difference

resistance opposing movement

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12
Q

lower resistance = _____ flow rate

A

higher

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13
Q

Higher resistance = ____ flow rate

A

lower

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14
Q

the total energy contained in moving fluid is the sum of

A

pressure (potential), kinetic and gravitational energy

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15
Q

Pressure

A

potential/stored energy

major form of energy for circulation of blood

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16
Q

pressure is expressed in

A

mmHg

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17
Q

Kinetic energy

A

velocity

small for circulating blood

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18
Q

kinetic energy is expressed in

A

fluid density and velocity measurements

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19
Q

gravitational energy

A 
equivalent to weight of column of blood extending from the heart to the level where pressure is measured
hydrostatic pressure (HP)
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20
Q

supine patient hydrostatic pressure

A

arteries and veins are at the same level as the heart

0mmHg against arteries and veins at ankle

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21
Q

standing patient hydrostatic pressure

A

at ankle pressure is about 100mmHg

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22
Q

a _____ is needed to move blood from one point to another

A

energy gradient

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23
Q

the greater the energy gradient the ____ the flow

A

greater

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24
Q

Inertia

A

tendency of fluid to resist chanegs in its velocity

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25
Q

as blood moves farther out to the periphery

A

energy is dissipated in the form of heat

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26
Q

energy is continually restored by the

A

pumping action of the heart

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27
Q

movement of fluid is dependent upon

A

physical properties of the fluid and

what is moving through

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28
Q

Resistance = 8 nl/r4pi

A 
R= resistance
n= viscosity of blood
l= length of the blood vessel
r^4= radius of blood vessel
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29
Q

Resistance is directly proportional to

A

viscosity and length

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30
Q

Resistance is inversely proportional to

A

radius of blood vessel

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31
Q

what has the most dramatic effect on resistance?

A

a change in vessel diameter

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32
Q

Internal friction within a fluid is measure by

A

it’s viscosity

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33
Q

Friction causes loss how

A

energy is lost in form of heat as rbcs rub together

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34
Q

elevated hematocrit _____ viscosity

A

increases

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35
Q

anemia ____ viscosity

A

decreases

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36
Q

Diminishing vessel size

A

increases frictional forces and heat energy loss

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37
Q

increase viscosity = _______ velocity

A

decreased

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38
Q

decrease viscosity = ____ velocity

A

increased

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39
Q

plug flow is seen at

A

vessel orgin

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40
Q

parabolic flow is usually seen

A

downstream

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41
Q

viscous energy loss is due to

A

increased friction between layer of blood

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42
Q

intertial losses occur

A

with deviations from laminar flow due to change in direction of velocity

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43
Q

what happens to the blood when deviations from laminar flow occur

A

parabolic flow profile becomes flattened

flow becomes disorganized

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44
Q

inertial energy loss typically occurs at

A

exit of a stenosis

45
Q

Posieuille’s equation defines

A

relationship between pressure, volume flow, resistance

46
Q

Poiseuille’s law helps answer the question

A

how much fluid moves through a vessel

47
Q

Poiseuille’s equation:

A

Q = P / R

Q= volume flow
P= Pressure
R= resistance
48
Q

Poiseuille’s equation and the relationship between contributors to flow itself

A

Q = (p1 - p2) pie r^4 / 8nL

Q= volume flow
P1 - P2 = pressures at proximal / dst ends
R = Radius of vessel
L = Length of vessel
n = viscosity of fluid
49
Q

Radius of the vessel is

A

directly proportional to volume flow

50
Q

the Law of Conservation of Mass explains what relationship

A

the relationship between velocity and area

51
Q

Law of Conservation of Mass equation

A

Q = A x V

52
Q

If area increases

A

velocity decreases

53
Q

if area decreases

A

velocity increases

54
Q

Bernoulli describes:

A

pressure and velocity relationship

55
Q

The total energy contained in a moving fluid is the sum of

A

pressure, kinetic and gravitational energies

56
Q

If there is a change in either kinetic, gravitational or pressure energies what happens

A

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

57
Q

if velocity increases, pressure

A

decreases

58
Q

if velocity decreases, pressure

A

increases

59
Q

pressure gradients are also known as

A

flow seperations

60
Q

flow separation occur because

A

geometry change with or without intra-luminal disease, curves

61
Q

in a flow separation velocity _____ and pressure ____

A

decreases

increases

62
Q

flow separations result in regions of

A

stagnant flow or little movement

63
Q

examples of flow separations include

A

bypass graft anastamosis site, valve cusp site

64
Q

Reynolds Number (Re)

A

determines when fluid becomes unstable / disturbed

65
Q

at which Reynolds number does laminar flow become turbulent

A

> 2000

66
Q

Steady flow originates from

A

steady driving pressure, predictable behavior

67
Q

in steady flow energy losses mainly occur from

A

viscous loss, can be described by poiseuille’s equation

68
Q

pulsatile flow

A

changes in both driving pressure condition as as well as response to the system

69
Q

Systole

A

forward flow throughout the periphery (fluid acceleration)

70
Q

late systole/ early diastole

A

temporary flow reversal

71
Q

late systole/early disatole is caused by

A

phase shifted negative pressure gradient and peripheral resistance

72
Q

late systole/early diastole causes

A

reflection of the wave proximally

73
Q

the dicrotic nothc is related to

A

closure of the aortic valve and influence of peripheral resistance

74
Q

Late diastole

A

flow is foward again

relective wave hits proximal resistance of the oncoming next wave and reverses

75
Q

low resistance flow

A

flow is continuous (steady) feeling a dilated vascular bed

76
Q

examples of low resistance flow

A

ICA, vertbral, renal, celiac, splenic, hepatic

77
Q

high resistance flow

A

pulsatile in nature

78
Q

what happens in high resistance flow

A

between pulses, hydraulic reflections travel back up vessel from the periphery producing flow reversals

79
Q

examples of high resistance flow vessels

A 
ECA
subclavian
aorta
iliac
extremity arteries
fasting sma
80
Q

the reversal of flow in a high resistance vessel may disappear distal to a stenosis because

A

of decreased peripheral resistance, secondary to ischemia

81
Q

doppler flow distal to a significant stenosis

A

lower resistance
more rounded in appearance
weaker in strength

82
Q

what happens to a normally high resistant signal as it approaches a significant stenosis

A

normally biphasic or triphasic signal may become monophasic

83
Q

doppler flow proximal to a significant stenosis is

A

higher resistant

could have no/minimal diastole

84
Q

during vasoconstriction, pulsatile changes in medium/small sized arteries of the limbs are

A

increased and pulsatility changes in minute arteries are decreased

85
Q

during vasodilation, pulsatile changes in medium/small sized arteries of the limbs are

A

decreased, lower resistant,

pulsatility changes are increased in minute arteries

86
Q

as the inflow pressure falls as a result of stenosis, what does the periphery do?

A

vasodilate to maintain flow

87
Q

at rest, total blood flow may be normal even in the presence of a stenosis/occluision.. why is this

A

development of a collateral network

compensatory decrease in peripheral resistance

88
Q

Arterial obstruction can cause changes in collateral channels near the site of obstruction, these changes include:

A

increased flow
reversed flow direction
increased velocity
waveform pulsatility changes

89
Q

location of collaterals can help provide information about what

A

location of stenosis or obstruction

90
Q

exercise should induce:

A

vasofilation

91
Q

vasodilation does what?

A

lowers distal peripheral resistance, increases blood flow

92
Q

what also influences vasoconstriction and vasodilation of blood vessels

A

sympathetic innervation fibers which help regulate body temperature

93
Q

what is the best single vasodilator of resistance vessels within skeletal muscles?

A

exercise

94
Q

autoregulation

A

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

95
Q

autoregulation is not present when

A

perfusion pressure drops below a critical level

96
Q

BP rise:

A

constriction of resistance vessels

97
Q

BP fall:

A

dilation of resistance vessels

98
Q

exercise usually decreases what in the exercising extremity

A

decreases reflection, decreases resistance

99
Q

what waveform is seen in extremity arteries after exercise

A

low resistant, monophasic caused by vasodilation

100
Q

with proximal arterial obstructions what happens to the flow patterns distally

A

monophasic wave form due to peripheral dilatation

101
Q

higher resistance signals may be seen when

A

vasoconstrction at the arteriolar level or distal arterial obstruction

102
Q

flow to cool extremity

A

pulsatile

103
Q

flow to warm extremity

A

continuous steady signal

104
Q

a cross sectional area reduction of 75% = ____ diameter reduction

A

50%

105
Q

effects of flow abnormality produced by a stenosis depends on 4 factors

A 
length, diameter, shape of narrowing
multiple obstructions (resistances are additive)
obstructions in parallel vessels
pressure gradient (peripheral resistance beyond stenosis)
106
Q

Proximal to a stenosis

A

flow is dampened

107
Q

at the stenosis entrance

A

increase in doppler shift frequencies
spectral broadening
elevated velocities

108
Q

flow disturbance in a stenosis occurs

A

due to interrupted flow stability with high velocity and eddies currents

109
Q

at the exit of a stenosis

A

flow reversals
flor separations
eddy currents
spectral broadening

Vascular Boards (30 decks)

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