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Ultrasound Physics > Ch. 18 Hemodynamics > Flashcards

Ch. 18 Hemodynamics Flashcards

(93 cards)

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1
Q

What are the 5 concepts of hemodynamics?

A

Blood
Blood pressure
Resistance
Cardiac Output
Regulation

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2
Q

What is blood flow influenced by?

A

pressure and resistance

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3
Q

What is blood pressure?

A

The force exerted by blood on the walls of the blood vessels.

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4
Q

What is resistance?

A

the resistance the blood flow must overcome to keep blood moving through the circulation

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5
Q

What is regulation?

A

the body’s use of neural and hormonal methods to help control a stable blood volume, flow and pressure

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6
Q

What is flow?

A

the VOLUME of blood moving during a particular TIME

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7
Q

What is another name for flow?

A

Volume flow rate

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8
Q

What are the units of flow?

A

volume/time, liters/min

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9
Q

What is velocity?

A

the speed of a fluid moving from one location to another

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10
Q

What are the 3 types of blood flow?

A

Pulsatile, Phasic, Steady

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11
Q

What is pulsatile flow?

A

Blood flow that accelerates and decelerates.

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12
Q

Does pulsatile flow occur in arteries or veins and how?

A

Arteries (during cardiac contraction)

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13
Q

What is phasic flow?

A

Blood flow that accelerates and decelerates as a result of RESPIRATION

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14
Q

Does phasic flow occur in arteries or veins?

A

Veins

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15
Q

What is steady flow?

A

Blood flow moves at a constant speed or velocity.

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16
Q

Does steady flow occur in arteries or veins and how?

A

Veins (when person holds their breath)

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17
Q

What is laminar flow?

A

the flow streamlines are aligned and parallel

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18
Q

What does streamlines mean?

A

Layers of blood

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19
Q

T/F Layers of blood travel at individual speeds during laminar flow.

A

True

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20
Q

What are the 2 types of laminar flow?

A

Plug and Parabolic

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21
Q

What is plug flow?

A

all streamlines move at the same velocity

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22
Q

What is parabolic flow? and what shape?

A

velocity is highest in the center and slowest along the wall due to friction (bullet shaped)

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23
Q

What is Reynolds number used for?

A

A number used to predict when flow is laminar or turbulent

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24
Q

When the Reynolds number is less than 1,500 what type of flow is it?

A

Laminar

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25
When the Reynolds number is more than 2,000 what type of flow is it?
Turbulent
26
What is turbulent flow?
Chaotic flow patterns in many different directions at many speeds.
27
What is turbulent flow made up of?
Eddy current and vortex
28
When is turbulent flow typically seen?
Downstream from a stenosis
29
What is murmur/bruit and thrill associated with what type of flow?
Turbulent flow
30
What is murmur/bruit?
when there is turbulence in an artery or in the heart (you can hear it)
31
What is thrill?
When tissue vibrates from turbulence (you can feel it)
32
If velocity increases, what happens to turbulence? (increases or decreases)
increases
33
If diameter increases, what happens to turbulence? (increases or decreases)
increases
34
If density increases, what happens to turbulence? (increase or decrease)
increase
35
If Viscosity increases, what happens to turbulence? (increase or decrease)
Decreases
36
What are the 3 forms of blood movement? (Energy)
Kinetic, Pressure, Gravitational energy
37
What is an energy gradient?
When blood moves from regions of high energy to low energy
38
What is kinetic energy?
Motion of blood and how its moving
39
What is kinetic energy determined by?
mass and speed
40
What is pressure energy? and it creates flow by overcoming what?
stored or potential energy resistance
41
Gravitational energy is _____ or ______ energy and what is it associated with?
Stored or potential energy elevated objects
42
What are the 3 ways energy is lost?
Viscous Frictional Inertial
43
What does viscous energy loss describe?
more energy is lost with movement of high viscosity fluids (thicker blood = high energy loss)
44
What are the units for viscosity?
Poise
45
What is hematocrit?
the percentage of blood made up of RBC's
46
What is frictional energy loss?
blood that is moving along a vessel wall leads to heat loss because of friction
47
What is inertial energy loss?
energy that is lost when the speed of a fluid changes.
48
What is inertia?
when a fluid tries to resist changes in its velocity
49
What are the 3 things that cause inertial energy loss?
Pulsatile flow Phasic flow Stenosis
50
What happens to velocity when it reaches a stenosis?
it increases
51
What happens to velocity AFTER the blood flows out of the stenosis?
It decreases
52
What type of flow is found downstream from a stenosis?
turbulent flow
53
What is a stenosis?
a narrowing in the lumen of a vessel
54
What is the velocity of blood BEFORE it reaches the stenosis?
normal
55
What type of effects does a stenosis have on blood flow?
-change in flow direction -leads to a pressure gradient -changes from pulsatile flow to steady flow -post-stenotic turbulence -increased velocity within the stenosis
56
What is post-stenotic turbulence?
turbulence downstream from the stenosis
57
What is Bernoulli’s prinicple?
The relationship between pressure and velocity in a moving fluid.
58
What is the relationship between pressure and velocity?
inversely related
59
_______energy + ______ energy = total energy
Potential energy + kinetic energy = total energy
60
In regard to the Law of Conservation, An increase in velocity results in a _______ in pressure.
decrease
61
In regard to the Law of Conservation, A decrease in velocity results in an ________ in pressure.
increase
62
Pressure gradient = ______ x _______.
pressure gradient = flow x resistance
63
If the pressure gradient increases, the flow will _______ and resistance will _______.
Increase flow and increase resistance
64
If the flow increases, the pressure gradient _________ and resistance _________.
increase pressure gradient and decrease resistance
65
What is the formula for Ohms law?
Voltage(pressure) = current(flow) x resistance
66
In the body there is pressure, what is the electrical name for fluid?
voltage
67
In the body there is flow, what is the electrical name for flow?
current
68
In the body there is resistance, what is the electrical name for resistance?
resistance in Ohms
69
Blood always flows from ____pressure to _____ pressure.
high to low
70
What is the flow rate determined by?
pressure gradient and resistance to flow
71
What is resistance to flow determined by? (3 things)
-viscosity of blood -length of the vessel -radius of the lumen
72
What is Poiseuille's law?
The relationship between flow rate, pressure difference, and resistance
73
Does a vein have low or high resistance?
low
74
What is the shape of a vein?
hourglass or flattened
75
Does a vein have high or low pressure?
low
76
What happens to a vein during exercise?
the blood flow will increase causing the vein to expand from hourglass shape to oval or circular shape
77
What is transmural pressure?
the difference in pressure within a vessel compared to outside the vessel.
78
What is low transmural pressure?
the force outside the vein is greater than inside the vein
79
what happens to hydrostatic pressure and transmural pressure when a person stands?
they both increase
80
What is hydrostatic pressure? What are the units?
Pressure of the weight of blood on a vessel mmHg
81
When a person is supine, what happens to the hydrostatic pressure?
zero
82
What happens to the hydrostatic pressure below the heart?
pressure is high
83
What happens to the hydrostatic pressure above the heart?
pressure is low
84
Measured pressure = ______pressure + _______ pressure.
circulatory pressure + hydrostatic pressure
85
What is a calf muscle pump?
contraction of calf muscle propels blood from lower extremities to the heart
86
What are venous valves?
keeps blood flowing in the right direction (towards the heart)
87
What is Intrathoracic pressure?
Inspiration and expiration change the intrathoracic flow to the heart.
88
What happens to the diaphragm during inspiration?
it moves down
89
What happens to the diaphragm during expiration?
it moves up
90
What happens to venous blood flow during inspiration. (increase or decrease)?
increases blood flow
91
What happens to venous blood flow in the legs during inspiration (Increase or decrease flow)?
Venous blood flow decreases
92
What happens to venous blood flow during expiration?
decreases blood flow
93
What happens to venous blood flow in the legs during expiration?
increases blood flow

Ultrasound Physics (13 decks)

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