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Ultrasound Vascular Technology > Physiology and Hemodynamics > Flashcards

Physiology and Hemodynamics Flashcards

1
Q

Multi-branched elastic conduit is set into oscillation by what?

A

each beat of the heart

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2
Q

Each beat of the heart pumps about how much blood into the aorta causing a blood pressure pulse?

A

70 milliliters

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3
Q

What are the 3 actions of a cardiac contraction?

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 arises
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4
Q

Increased hear rate delivers what?

A

An increased blood volume

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5
Q

The heart pump generates what?

A

the pressure to move the blood

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6
Q

The heart pump results in what?

A

A pressure wave (energy wave) that travels rapidly throughout the system, demonstrating transformation as it travels distally.

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7
Q

Pumping action the heart results in what?

A

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

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8
Q

Cardiac output governs the amount of:

A

The blood that enters the arterial system: arterial pressure and total peripheral resistance, determines the amount that leaves it.

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9
Q

Pressure is greatest where?

A

The heart

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10
Q

Movement of any fluid medium between two points require two things:

A
  1. A pathway along which the fluid can flow
  2. Difference in energy levels (pressure difference)
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11
Q

The amount of flow depends on:

A
  1. Energy difference: includes losses resulting from fluid movement

2.Any resistance which tends to oppose such movement

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12
Q

lower resistance =

A

higher flow rate

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13
Q

higher resistance =

A

lower flow rate

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14
Q

The total energy contained in moving fluid is the sum of what?

A

Pressure (potential)
Kinetic and gravitational energies

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15
Q

Describe pressure energy:

A

Sideways flow*

  • Stored energy
  • Major form of E for circulation of blood
  • Expressed in mmHg
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16
Q

Describe kinetic energy (velocity):

A

Forward flow*

  • Small for circulating blood
  • Expressed in terms of fluid density and its velocity measurements
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17
Q

What happens at the same time of heart contractions?

A

Pressure and Kinetic energy (velocity)

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18
Q

What is gravitational energy also called?

A

Hydrostatic pressure (HP)

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19
Q

Gravitational energy is equivalent to what?

A

The weight of the column of blood extending from the heart to level where pressure is measured

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20
Q

When standing, HP increases, adding about

A
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20
Q

When standing, HP increases, adding about:

A

100 mmHg against ankle vessels

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21
Q

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

A

Energy gradiant

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22
Q

The greater the gradient:

A

greater the flow!

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23
Q

_____________ : relates to the tendency of a fluid to resist changes in its velocity.

A

Inertia

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24
Q

As the blood moves farther out of periphery, what happens to the energy?

A

it dissipates largely in the form of heat

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25
Q

Energy is continually restored by what?

A

Pumping action of the heart

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26
Q

Movement of a fluid (blood) is dependent on:

A

physical properties of the fluid and what its moving through

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27
Q

R =
n =
r =
L =

A

R = Resistance
n = viscosity
r = radius
L = vessel length

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28
Q

R =

A

R = 8nL / pie r^4

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29
Q

What has the most dramatic effect on resistance?

A

vessel diameter

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30
Q

Internal friction within a fluid is measured by:

A

viscosity

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31
Q

Elevated hematocrit increases blood ________.

A

viscosity

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32
Q

Severe anemia decreases blood __________.

A

viscosity

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33
Q

May use hematocrit instead of ___________.

A

viscosity

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34
Q

Diminishing vessel size leads to:

A

increases frictional forces and heat energy losses

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35
Q

increased viscosity =

A

low velocity

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36
Q

Laminar flow consists of:

A

layers of fluid particles moving against one another

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37
Q

Laminal flow looks like:

A

fast flow in the center and stationary flow at the wall

38
Q

What flow is considered stable?

A

Laminar

39
Q

Where is plug flow seen?

A

At vessels origin

40
Q

Parabolic profile of laminar flow is seen?

A

usually downstream

41
Q

Viscous is also known as:

A

Thickness

42
Q

Viscous energy loss is due to:

A

Increased friction between molecules and layers which ultimately causes energy loss

43
Q

Inertial losses occur with what:

A

Deviations from laminal low, due to changes in direction and/or velocity

has biggest change

44
Q

What 3 things happen with energy losses?

A
  1. The parabolic flow profile becomes flattened
  2. Flow moves in a disorganized fashion

3.This type of energy loss occurs at the exit of a stenosis

45
Q

Poiseuille’s equation defines relationships between what?

A

pressure
volume flow
resistance

46
Q

What helps answer the question of “how much fluid moves through vessel”?

A

Poiseuille’s equation

47
Q

What is Poiseuille’s equation?

A

Q = P / R

Q = volume
P = pressure
R = resistance

48
Q

Poiseuille’s equation:

Increase in P =
Increase in R =

A

Increase in P = Increase in Q
Increase in R = Decrease in Q

49
Q

Q = (P1 - P2) pie R^4 / 8 n L

A

Q = Volume Flow
P1 - P2 = Pressure at proximal/distal ends
r = Radius of the tube
L - Length of the tube
n = viscosity of the fluid

50
Q

What has the most dramatic effect on resistance?

A

Diameter change

51
Q

Radius (r^4) of vessel is directly proportional to what?

A

Volume flow

52
Q

Small changes in radius may result in;

A

large changes in volume flow

53
Q

The Law of Conservation of Mass explains the relationship between:

A

velocity and area

(Q = A x V)

54
Q

Total energy contained in moving fluid is the sum of what?

A

Pressure, kinetic and gravitational energies

55
Q

Why do pressure gradients (slow separations) occur?

A

Because of a geometry change with or without intra-luminal disease and because of curves

56
Q

Flow separations result in what?

A

Regions with stagnant or little movement

57
Q

What does Reynolds Number (RE) predict?

A

when fluid becomes unstable/disturbed

58
Q

What is reynolds number?

A

> 2000, means laminar flow tends to become disturbed

59
Q

In a rigid tube, energy losses are mainly:

A

Viscous

60
Q

What flow changes both the driving pressure condition as well as the response of the system?

A

Pulsatile flow

61
Q

___________: forward flow throughout the periphery (fluid acceleration).

A

Systole

62
Q

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

A

Late systole/Early diastole

63
Q

The dicrotic notch is related to what?

A

the closure of the aortic valve and the influence of peripheral resistance

64
Q

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

A

Late diastole

65
Q

_______________ : flow of a continuous (steady_ nature feeding a dilated vascular bed

A

Low resistance

66
Q

What type of flow is seen in organs?

A

Low resistance

67
Q

Example arteries of low resistance flow:

A

ICA
Vertebral
Renal
Celiac
Splenic
Hepatic

68
Q

______________: flow of a pulsatile nature. Between incident pulses, hydraulic reflections travel back up the vessel from the periphery producing flow reversals in the vascular compartment

A

High resistance flow

69
Q

Example arteries of high resistance flow:

A

ECA
Subclavian
Aorta
Iliac
Extremity arteries
Fasting SMA

70
Q

The reversal component of a high resistant signal may disappear distal to a stenosis because:

A

decreased peripheral resistance, secondary to ischemia

71
Q

Doppler flow distal to a significant stenosis is ___________.

A

lower resistance

  • more rounded in appearance and is weaker in strength
72
Q

A normally high resistant (biphasic or triphasic) signal may become monophasic as it approaches what?

A

the significant stenosis and/or aterial obstruction

73
Q

Doppler flow proximal to a significant stenosis has what kind of resistance?

A

higher resistance in quality

74
Q

What happens with vasoconstrictions?

A

Pulsatile changes in medium/small sized arteries of the limbs are increased. When this occurs, pulsatility changes are usually decreased in the minute arteries.

75
Q

What happens with vasodilatation?

A

Pulsatile changes in medium/small sized arteries of the limbs are decreased (lower resistance). When this occurs, pulsatility changes are increased in minute arteries.

76
Q

What is the natural response in the periphery as the inflow pressure falls as a result in stenosis?

A

vasodilate to maintain flow

77
Q

Arterial obstruction may alter flow in collateral channels nearby or further away from site of obstruction. Changes include:

A
  1. Increased volume flow
  2. Reversed flow direction
  3. Increased velocity
  4. Waveform pulsatility changes
78
Q

What induces peripheral vasodilatation and lowers the distal peripheral resistance, increasing blood flow?

A

Exercise

79
Q

Vasoconstriction and vasodilation of blood vessels within skeletal muscles also influenced by sympathetic innervation fibers functioning primary for _________.

A

Regulation of body temperature

80
Q

What is the ability of most vascular beds to maintain constant level of blood flow over a wide range or perfusion pressures?

A

Autoregulation

81
Q

BP rise = ________________ of resistance vessels

A

constrictions

82
Q

Flow to a cool extremity (vasoconstriction) will have what type of signal?

A

pulsatile

83
Q

Flow to a warm extremity (vasodilation) will have what type of signal?

A

continuous and steady

84
Q

Distal effects of obstructive disease may only be detectable following:

A

stress

85
Q

A hemodynamically significant stenosis causes a notable reduction in what?

A

volume flow and pressure

86
Q

Cross sectional area reduction of 75% = diameter reduction of __________.

A

50%

87
Q

Effects of flow abnormality produced by a stenosis depends on factors such as:

A
  1. Length, diameter, shape, degree of narrowing
  2. Multiple obstruction in the same vessel: resistance to flow is additively it results in a higher resistance than in each individual narrowing
  3. Obstructions in different vessels that are parallel: resistance to flow is less than the resistance in each individual narrowing because only part of the blood flow is going through each narrowing
  4. Pressure gradient; peripheral resistance beyond stenosis
88
Q

Where are flow frequencies usually dampened, with or without disturbance?

A

Proximal to a stenosis

89
Q

Entrance into the stenosis produces an increase in Doppler shift frequencies (DSF), resulting in what?

A

Spectral broadening and elevated velocities

90
Q

Flow disturbance occurs due to what?

A

Interrupted flow stability with high velocities and eddy currents

91
Q

Where is post-stenotic turbulence seen?

A

At stenosis exit, flow reversals, flow separations, vortices / eddy currents occur near edge of flow pattern.

92
Q

Post-stenotic turbulence flow quality is compromised of what?

A

multiple changes in direction and spectral broadening as displayed by the spectral pattern

Ultrasound Vascular Technology (12 decks)

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