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Ultrasound Physics > Ch 18: Hemodynamics > Flashcards

Ch 18: Hemodynamics Flashcards

1
Q

This indicates the volume of blood moving during a particular time.

A

flow (aka volume flow rate)

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2
Q

Flow is measured in units of…

A

volume divided by time (L/min)

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3
Q

This indicates the speed of a fluid moving from one location to another.

A

velocity

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4
Q

Velocity is measured in units of…

A

distance divided by time (cm/s)

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5
Q

Three basic forms of flow…

A
  1. pulsatile
  2. phasic
  3. steady
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6
Q

This kind of flow occurs when blood moves with a variable velocity as a result of cardiac contraction.

A

pulsatile flow

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7
Q

This kind of flow commonly appears in the arterial circulation.

A

pulsatile flow

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8
Q

This kind of flow occurs when a fluid moves with a variable velocity as a result of respiration.

A

phasic

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9
Q

This kind of flow commonly appears in the venous circulation.

A

phasic

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10
Q

This kind of flow occurs when a fluid moves at a constant speed.

A

steady

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11
Q

This kind of flow is present in the venous circulation when individuals stop breathing for a moment.

A

steady

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12
Q

This is when the flow streamlines are aligned and parallel.

A

laminar flow

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13
Q

The word lamina means…

A

layer

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14
Q

Laminar flow patterns are commonly found in __ physiologic states.

A

normal

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15
Q

This flow occurs when all of the layers and blood cells travel at the same velocity.

A

plug flow

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16
Q

This flow has a bullet-shaped profile with the highest velocity in the center of the lumen.

A

parabolic flow

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17
Q

T/F? Laminar flow is silent flow.

A

true

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18
Q

This predicts whether flow is laminar or turbulent.

A

Reynold’s number

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19
Q

The Reynolds number for laminar flow is…

A

less than 1500.

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20
Q

This flow is characterized by chaotic patterns in many different directions and at many speeds.

A

turbulent

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21
Q

This is a small swirling rotational pattern appearing in turbulent flow.

A

eddy current or vortex

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22
Q

T/F? Turbulent flow is often normal.

A

FALSE, pathologic

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23
Q

This is tissue vibration associated with turbulence, a palpable murmur.

A

thrill

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24
Q

The Reynolds number for turbulent flow is…

A

greater than 2000.

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25
Q

Blood moves from regions of higher energy to lower energy. This is called…

A

energy gradient

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26
Q

Three forms of energy associated with blood…

A
  1. kinetic
  2. pressure
  3. gravitational
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27
Q

The energy associates with a moving object is…

A

kinetic

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28
Q

Kinetic energy is determined by two factors…

A
  1. an object’s mass

2. the speed at which it moves

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29
Q

The energy associated with stored or potential energy is…

A

pressure

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30
Q

This energy is associated with any elevated object.

A

gravity

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31
Q

T/F? Identical objects at the same height have the same gravitational energy.

32
Q

The three ways energy is lost in the circulation:

A
  1. viscous loss
  2. frictional loss
  3. inertial loss
33
Q

This describes the thickness of a fluid.

34
Q

Viscosity is measured in units of..

35
Q

This is the percentage of blood made up of red blood cells.

A

hematocrit

36
Q

This occurs when flow energy is converted to heat as one object rubs against another.

A

frictional energy loss

37
Q

This is related to the tendency of a fluid to resist changes in its velocity.

38
Q

Inertial energy loss in velocity changes in…

39
Q

Maximum velocity exists where the vessel is…

A

narrowest.

40
Q

This is a narrowing in the lumen of a vessel.

41
Q

Stenosis __ the blood’s direction.

42
Q

Stenosis __ the blood’s velocity.

43
Q

This is turbulence downstream from the stenosis.

A

post-stenotic turbulence

44
Q

The pressure downstream from the stenosis is __ than the pressure upstream.

45
Q

T/F? Flow stays pulsatile after passing througha stenosis.

A

FALSE, it becomes steady

46
Q

This describes the relationship between velocity and pressure in a moving fluid.

A

Bernoulli’s principle

47
Q

This is derived from the principle of conservation of energy.

A

Bernoulli’s principle

48
Q

flow x resistance =

A

pressure gradient

49
Q

Pressure gradient increases when either…

A
  1. flow increases

2. resistance increases

50
Q

Flow increases when either…

A
  1. pressure gradient increases

2. resistance decreases

51
Q

current x resistance =

52
Q

In an electrical system, pressure is called…

53
Q

In an electrical system, flow is called…

54
Q

Electrical resistance is measured in units of…

55
Q

In the circulatory system, the resistance vessels are called…

A

arterioles.

56
Q

Veins are usually __ resistance vessels.

57
Q

When venous inflow increases, the cross-sectional shape of a vein…

A

changes from hourglass to oval to round.

58
Q

Normal veins increase flow with a __ increase in pressure.

59
Q

This is the pressure related to the weight of blood pressing on a vessel measured at a height above or below heart level.

A

hydrostatic pressure

60
Q

Hydrostatic pressure is reported in units of…

61
Q

circulatory pressure + hydrostatic pressure =

A

measured pressure

62
Q

Hydrostatic pressure at the ankle

63
Q

Hydrostatic pressure at the knee

64
Q

Hydrostatic pressure at the waist

65
Q

Hydrostatic pressure at the midchest

66
Q

Hydrostatic pressure at the top of head

67
Q

Respiration affects venous flow for two reasons…

A
  1. venous systems are low pressure

2. it alters pressures in the thorax and abdomen

68
Q

During inspiration, the diaphragm moves…

69
Q

When the chest cavity expands, it creates __ pressure in the chest.

70
Q

Negative thoracic pressure __ venous return.

71
Q

When the chest cavity expands, it creates __ pressure in the abdomen.

72
Q

Positive abdominal pressure __ venous return.

73
Q

During expiration, the diaphragm moves…

74
Q

When the chest cavity contracts, it creates __ pressure in the chest.

75
Q

Increased thoracic pressure __ venous return.

76
Q

When the chest cavity contracts, it creates __ pressure in the abdomen.

77
Q

Decreased abdominal pressure __ venous return.

Ultrasound Physics (23 decks)

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