Chapter 2: Physiology and Hemodynamics Flashcards
1
Q
each heart beat pumps about _____mLs of blood into the aorta
A
70
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
3
Q
Increased heart rate delivers _____ blood volume
A
increased
4
Q
The heart pump:
A
generates pressure to move the blood
results in pressure wave (energy wave) that travels through the system
5
Q
blood flow through system
A
lt ventricle aorta large arteries arterioles capillaries venules large veins vena cava rt atrium
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
7
Q
cardiac output governs
A
the amount of blood that enters the arterial system
8
Q
what determines the amount of blood that leaves the arterial system
A
arterial pressure and total peripheral resistance
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
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)
11
Q
the amount of flow depends on
A
energy difference
resistance opposing movement
12
Q
lower resistance = _____ flow rate
A
higher
13
Q
Higher resistance = ____ flow rate
A
lower
14
Q
the total energy contained in moving fluid is the sum of
A
pressure (potential), kinetic and gravitational energy
15
Q
Pressure
A
potential/stored energy
major form of energy for circulation of blood
16
Q
pressure is expressed in
A
mmHg
17
Q
Kinetic energy
A
velocity
small for circulating blood
18
Q
kinetic energy is expressed in
A
fluid density and velocity measurements
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)
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
21
Q
standing patient hydrostatic pressure
A
at ankle pressure is about 100mmHg
22
Q
a _____ is needed to move blood from one point to another
A
energy gradient
23
Q
the greater the energy gradient the ____ the flow
A
greater
24
Q
Inertia
A
tendency of fluid to resist chanegs in its velocity
25
as blood moves farther out to the periphery
energy is dissipated in the form of heat
26
energy is continually restored by the
pumping action of the heart
27
movement of fluid is dependent upon
physical properties of the fluid and
| what is moving through
28
Resistance = 8 nl/r4pi
```
R= resistance
n= viscosity of blood
l= length of the blood vessel
r^4= radius of blood vessel
```
29
Resistance is directly proportional to
viscosity and length
30
Resistance is inversely proportional to
radius of blood vessel
31
what has the most dramatic effect on resistance?
a change in vessel diameter
32
Internal friction within a fluid is measure by
it's viscosity
33
Friction causes loss how
energy is lost in form of heat as rbcs rub together
34
elevated hematocrit _____ viscosity
increases
35
anemia ____ viscosity
decreases
36
Diminishing vessel size
increases frictional forces and heat energy loss
37
increase viscosity = _______ velocity
decreased
38
decrease viscosity = ____ velocity
increased
39
plug flow is seen at
vessel orgin
40
parabolic flow is usually seen
downstream
41
viscous energy loss is due to
increased friction between layer of blood
42
intertial losses occur
with deviations from laminar flow due to change in direction of velocity
43
what happens to the blood when deviations from laminar flow occur
parabolic flow profile becomes flattened
| flow becomes disorganized
44
inertial energy loss typically occurs at
exit of a stenosis
45
Posieuille's equation defines
relationship between pressure, volume flow, resistance
46
Poiseuille's law helps answer the question
how much fluid moves through a vessel
47
Poiseuille's equation:
Q = P / R
```
Q= volume flow
P= Pressure
R= resistance
```
48
Poiseuille's equation and the relationship between contributors to flow itself
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
Radius of the vessel is
directly proportional to volume flow
50
the Law of Conservation of Mass explains what relationship
the relationship between velocity and area
51
Law of Conservation of Mass equation
Q = A x V
52
If area increases
velocity decreases
53
if area decreases
velocity increases
54
Bernoulli describes:
pressure and velocity relationship
55
The total energy contained in a moving fluid is the sum of
pressure, kinetic and gravitational energies
56
If there is a change in either kinetic, gravitational or pressure energies what happens
the other make up for the difference in order to maintain the original total fluid energy amount
57
if velocity increases, pressure
decreases
58
if velocity decreases, pressure
increases
59
pressure gradients are also known as
flow seperations
60
flow separation occur because
geometry change with or without intra-luminal disease, curves
61
in a flow separation velocity _____ and pressure ____
decreases
| increases
62
flow separations result in regions of
stagnant flow or little movement
63
examples of flow separations include
bypass graft anastamosis site, valve cusp site
64
Reynolds Number (Re)
determines when fluid becomes unstable / disturbed
65
at which Reynolds number does laminar flow become turbulent
> 2000
66
Steady flow originates from
steady driving pressure, predictable behavior
67
in steady flow energy losses mainly occur from
viscous loss, can be described by poiseuille's equation
68
pulsatile flow
changes in both driving pressure condition as as well as response to the system
69
Systole
forward flow throughout the periphery (fluid acceleration)
70
late systole/ early diastole
temporary flow reversal
71
late systole/early disatole is caused by
phase shifted negative pressure gradient and peripheral resistance
72
late systole/early diastole causes
reflection of the wave proximally
73
the dicrotic nothc is related to
closure of the aortic valve and influence of peripheral resistance
74
Late diastole
flow is foward again
| relective wave hits proximal resistance of the oncoming next wave and reverses
75
low resistance flow
flow is continuous (steady) feeling a dilated vascular bed
76
examples of low resistance flow
ICA, vertbral, renal, celiac, splenic, hepatic
77
high resistance flow
pulsatile in nature
78
what happens in high resistance flow
between pulses, hydraulic reflections travel back up vessel from the periphery producing flow reversals
79
examples of high resistance flow vessels
```
ECA
subclavian
aorta
iliac
extremity arteries
fasting sma
```
80
the reversal of flow in a high resistance vessel may disappear distal to a stenosis because
of decreased peripheral resistance, secondary to ischemia
81
doppler flow distal to a significant stenosis
lower resistance
more rounded in appearance
weaker in strength
82
what happens to a normally high resistant signal as it approaches a significant stenosis
normally biphasic or triphasic signal may become monophasic
83
doppler flow proximal to a significant stenosis is
higher resistant
| could have no/minimal diastole
84
during vasoconstriction, pulsatile changes in medium/small sized arteries of the limbs are
increased and pulsatility changes in minute arteries are decreased
85
during vasodilation, pulsatile changes in medium/small sized arteries of the limbs are
decreased, lower resistant,
| pulsatility changes are increased in minute arteries
86
as the inflow pressure falls as a result of stenosis, what does the periphery do?
vasodilate to maintain flow
87
at rest, total blood flow may be normal even in the presence of a stenosis/occluision.. why is this
development of a collateral network
| compensatory decrease in peripheral resistance
88
Arterial obstruction can cause changes in collateral channels near the site of obstruction, these changes include:
increased flow
reversed flow direction
increased velocity
waveform pulsatility changes
89
location of collaterals can help provide information about what
location of stenosis or obstruction
90
exercise should induce:
vasofilation
91
vasodilation does what?
lowers distal peripheral resistance, increases blood flow
92
what also influences vasoconstriction and vasodilation of blood vessels
sympathetic innervation fibers which help regulate body temperature
93
what is the best single vasodilator of resistance vessels within skeletal muscles?
exercise
94
autoregulation
ability of most vascular beds to maintain a constant level of blood flow over a wide range of perfusion pressures
95
autoregulation is not present when
perfusion pressure drops below a critical level
96
BP rise:
constriction of resistance vessels
97
BP fall:
dilation of resistance vessels
98
exercise usually decreases what in the exercising extremity
decreases reflection, decreases resistance
99
what waveform is seen in extremity arteries after exercise
low resistant, monophasic caused by vasodilation
100
with proximal arterial obstructions what happens to the flow patterns distally
monophasic wave form due to peripheral dilatation
101
higher resistance signals may be seen when
vasoconstrction at the arteriolar level or distal arterial obstruction
102
flow to cool extremity
pulsatile
103
flow to warm extremity
continuous steady signal
104
a cross sectional area reduction of 75% = ____ diameter reduction
50%
105
effects of flow abnormality produced by a stenosis depends on 4 factors
```
length, diameter, shape of narrowing
multiple obstructions (resistances are additive)
obstructions in parallel vessels
pressure gradient (peripheral resistance beyond stenosis)
```
106
Proximal to a stenosis
flow is dampened
107
at the stenosis entrance
increase in doppler shift frequencies
spectral broadening
elevated velocities
108
flow disturbance in a stenosis occurs
due to interrupted flow stability with high velocity and eddies currents
109
at the exit of a stenosis
flow reversals
flor separations
eddy currents
spectral broadening
