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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
as the blood moves farther out to the periphery, energy is dissipated as what?
heat
26
how is energy restored?
by the pumping action of the heart
27
what is movement of a fluid is dependent upon what?
physical properties of the fluid and what its moving through
28
what is the formula for resistance?
r= 8nL/pie R4
29
what has the most influence on resistance?
a change in vessel diameter
30
internal friction within a fluid is measured by what?
viscosity
31
what are some friction measured by viscosity?
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
32
what does diminishing vessel size increase?
increases frictional forces and heat energy losses
33
what is the relationship between velocity and viscosity?
inversely
34
what is laminar flow?
layers of fluid particles moving against one another
35
where is the fastest moving particles?
in the center
36
where is stationary flow at?
remains at the walls
37
what is laminar flow considered?
stable flow
38
what is plug flow?
blunted flow is likely seen at vessel origin ]
39
what is parabolic flow?
profile of laminar flow usually seen downstream | >
40
what is viscous energy losses due to?
increased friction between molecules and layers which causes energy losses
41
what is inertial losses due to?
occur with deviations form laminar flow due to changes in direction and/or velocity
42
what are some characteristics of inertial losses?
- 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
what is poiseuilles equation?
flow=pressure/resistance
44
which equation helps answer the question of how much fluid moves through a vessel?
poiseuilles
45
what is ohms law?
current=voltage/resistance I=V or E/R
46
what are other two ways to write poiseullies equation?
Q= (P) pie R4/8nL Q= (p1-p2)pieR4/8nL Q= AxV P1-P2- pressures at proximal/distal ends
47
what is the relationship between radius and volume flow?
directly
48
which principle explains the relationship b/w velocity and pressure?
bernoulli
49
if there is a change to one of the total energy what happens?
the other make up for the difference in order to maintain the original total fluid energy amount
50
what is the relationship between velocity and pressure?
inversely
51
why do pressure gradients (flow separations) occur?
geometry change with or without intra-luminal disease and b/c of curves e.g bulb tortuous vessel
52
where flow separations result in?
in regions with stagnant or little movement | e.g bypass graft anastomosis site, or valve cusp site
53
where does steady flow originate from?
from a steady driving pressure
54
what are some characteristics of steady flow?
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
what is pulsatile flow?
changes both the driving pressure conditions as well as the response of the system
56
what are some characteristics of systole?
forward flow throughout the periphery | fluid acceleration
57
what are some characteristics of late systole/ early diastole?
temporary flow reversal, due to a phase shifted negative pressure gradient and peripheral resistance, causing reflection of the wave proximally
58
what are some characteristics of late diastole?
flow is forward again, as reflective wave hits the proximal resistance of the next oncoming wave, and reverses
59
what is low resistance flow?
flow of a continuous steady nature feeding a dilated vascular bed
60
what vessels are low resistive?
ICA, verts, renal, celiac, splenic, hepatic, non fasting SMA
61
what is high resistance flow?
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
what vessels are high resistive?
ECA, subclavian, aorta, iliac, extremity arteries, fasting SMA
63
what can happen to the reversal component of a high resistant signal distal to a stenosis?
it may disappear due to decreased peripheral resistance, secondary to ischemia
64
what does the doppler flow distal to a stenosis look like?
lower resistant more rounded in appearance and is weaker in strength tardus parvus
65
what can happen to a high resistive waveform as it approaches a stenosis?
it can go from tiphasic to monophasic
66
what does the doppler flow proximal to a stenosis look like?
higher resistant | could have no diastole or minimal diastole
67
what happens with vasoconstriction?
pulsatile changes in the medium/small sized arteries of the limbs are increased. the pulsatility changes are usually decreased in the minute arteries
68
what waveform is normally seen with vasoconstriction?
high resistive
69
what waveform is normally seen with vasodilation?
low resistive
70
what happens with vasodilation?
pulsatile changes in the medium/small sized arteries of the limbs are decreased. while in the minute arteries are increased
71
as the inflow pressure falls as a result of stenosis, what is the peripheries natural response? vasodilate or vasocontrict
vasodilate
72
why can total blood flow be fairly normal due to collaterals?
development of a collateral network and a compensatory decrease in peripheral resistance
73
what changes occur with collaterals?
increased volume flow reversed flow direction increased velocity waveform pulsatility changes
74
T/F location of collaterals help provide tentative location of the obstruction
true
75
what effect does exercise have?
exercise should induce peripheral vasodilation which lower the distal peripheral resistance, increasing blood flow
76
what is the best single vasodilator of resistance to vessels?
exercise
77
what is augoregulation?
ability of most vascular beds to maintain constant level of blood flow over a wide range of perfusion pressures
78
what changes occur when BP rises?
constriction of vessels | vasoconstriction
79
what changes occur when BP falls?
dilation of vessels | vasodilation
80
does exercise increase or decrease reflection?
decrease
81
flow to a cool extremity will have what kind of signals?
pulsatile signals | vasoconstriction
82
flow to a warm extremity will have what kind of signals?
continuous, steady signals | vasodilation
83
T/F pulsatiliy changes do differentiate well between occusion and severe stenosis?
false
84
T/f waveforms may not be altered with good colateralization
true
85
T/F distal effects of obstructive disease may only be detectable following stress
true
86
T/F a hemodynamically significant stenosis does not cause a notable reduction in volume flow and pressure
false
87
what happens when cross sectional area reduction of 75%?
diameter reduction by 50%
88
where are lower frequencies distributed?
at walls, boundary layer
89
where are high frequencies distributed?
centerstream
90
what factors does effects of flow abnormality produced by a stenosis depend on?
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
what happens pre stenosis?
flow frequencies are usually dampened, with or without disturbance
92
what happens at stenosis?
increase in doppler shift frequencies, resulting in spectral broadening and elevated velocities
93
why do flow distrubances occur?
occurs due to interrupted flow stability with high velocities and eddy currents
94
what happens post stenosis?
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
what are abnormal jet?
elevated velocities

RVT Review (30 decks)

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