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Hemodynamic and Doppler > Ch 18 Book > Flashcards

Ch 18 Book Flashcards

1
Q

Hemodynamic

A

study of blood moving through the circulatory system

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2
Q

Flow indicates

Units

A

volume of blood moving during a particular time

liters/min, L/min

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3
Q

Velocity indicates

Units

A

speed or swiftness of a fluid moving from one location to another

cm/s

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4
Q

Pulsatile Flow

A

occurs when blood moves with a variable velocity

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5
Q

Pulsatile Flow: Blood accelerates and decelerates b/c

A

cardiac contraction

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6
Q

Pulsatile Flow: Present in

A

arterial circulation

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7
Q

Phasic flow

A

occurs when blood moves with a variable velocity

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8
Q

Phasic flow: Blood accelerates and decelerates b/c

A

respiration

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9
Q

Phasic flow: Present in

A

venous circulation

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10
Q

Steady Flow

Ex:

A

occurs when a fluid moves at a constant speed or velocity

water flowing through a hose

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11
Q

Steady Flow: Present in

A

venous circulation when individual stop breathing for a brief moment

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12
Q

Laminar flow

A

when the flow streamlines are aligned and parallel

Characterized by layer of blood that travels at individual speeds

Commonly found in normal physiologic status

Silent flow

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13
Q

Laminar flow forms: Plug flow

A

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

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14
Q

Laminae flow forms: Parabolic flow

A

has a bullet-shaped profile.

Velocity is highest in the center

Gradually decreases to its minimum at the vessel wall

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15
Q

Turbulent flow

A

characterized as chaotic flow patterns in many different directions and at many speeds

Associated with cardiovascular pathology and elevated blood velocities

Found downstream from stenosis

Converts flow energy into other forms such as sound and vibration

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16
Q

Vortex

A

Small, hurricane like, swirling, rotational patterns appear

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17
Q

Murmur or Bruit

A

Sound associated with turbulence

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18
Q

Thrill

A

associated with turbulence

Described as a palpable murmur

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19
Q

Reynolds number

A

predicts whether flow is laminar or turbulent

2,000 = turbulent

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20
Q

Energy Gradient

A

Blood moves from regions of higher energy to lower energy

Energy is imparted to blood by the contraction of the heart during systole

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21
Q

Kinetic Energy

A

Associated with a moving object

Heavy moving objects have lots of kinetic energy as slow moving objects have little

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22
Q

Kinetic Energy:

Determined by two factors:

A

An object’s mass

The speed at which it moves

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23
Q

Pressure Energy

A

A form of stored or potential energy

Potential energy has the ability to perform work

major form of energy for circulating blood and creates flow by overcoming resistance

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24
Q

Gravitation Energy

Associated with

A

A form of stored or potential energy

elevated object

All elevated objects have stored energy (gravitation energy) that can perform work.

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25
Q

Viscous Energy Loss

A

Describes the thickness of a fluid

More energy is lost with movement of high viscosity

Loss is associated with blood overcoming its internal stickiness and determined by the hematocrit

26
Q

Viscous Energy Loss: Hematocrit

A

percentage of blood made up of red blood cells

Normal value is 45%

Anemia, hematocrit reduced and blood has a reduced viscosity

Units: Poise

27
Q

Frictional Energy Loss

A

Occur when flow energy is converted to heat as one object rubs against another

Blood sliding across vessel walls creates heart

28
Q

Inertial Energy Loss

A

“Objects at rest tend to stay at rest and objects in motion tend to stay in motion” – Sir Isaac Newton

Energy is lost when the speed of a fluid changes, regardless of whether the fluid speeds up or slows down

29
Q

Inertial Energy Loss: Inertia relates to

A

tendency of a fluid to resist changes in its velocity

30
Q

Inertial energy loss occurs during three events

A

Pulsatile flow (arterial)

Phasic Flow (venous)

Velocity changes at a stenosis

31
Q

Inertial Energy Loss: Velocity

A

Velocity increases as the vessel narrows

Maximum velocity exists where the vessel is narrowest
Velocity decreases as blood flows out of the stenosis into a vessel segment of normal diameter

32
Q

Stenosis

A

Narrowing in the lumen of a vessel

33
Q

Stenosis Effects

A 
change in flow direction
increased velocity as vessel narrows
turbulence downstream from the stenosis
pressure gradient across the stenosis
loss of pulsatility
34
Q

Stenosis Effects: increased velocity within the stenosis

A

highest where vessel is narrowest

35
Q

Stenosis Effect: turbulence downstream from stenosis

A

post stenotic turbulence

Lumen expands more dramatically than the streamlines of blood flow are able to fill it

Streamlines are destroyed and turbulence appears

Converted to sound (bruit) or vibrations (thrill) or both

36
Q

Stenosis Effect: Pressure gradient across the stenosis

A

the pressure downstream from the stenosis is lower than the pressure upstream

decreases the results from the loss of energy as blood moves through the stenosis

37
Q

Bernoulli’s Principle describes

A

relationship between velocity and pressure in a moving fluid

38
Q

Bernoulli’s Principle derived from

A

the principle of conservation of energy

39
Q

Bernoulli’s Principle states

A

with a steady flow, the sum of all forms of energy is same everywhere

The sum of kinetic energy and pressure energy remains constant

40
Q

Bernoulli’s Principle: The Law of Conservation of Energy

A

states that energy is neither created nor destroyed, it is converted from one form to another

41
Q

Arterioles

A

resistance vessels

42
Q

Pressure gradient =

A

flow x resistance

43
Q

Pressure gradient increase when either

A

Flow increases

Resistance increases

44
Q

Flow increases when either

A

Pressure gradient increases

Resistance decreases

45
Q

Fluids vs Electricity

Fluids: Pressure
Electricity: ______

A

Voltage

46
Q

Fluids vs Electricity

Fluids: Flow
Electricity: ______

A

Current

47
Q

Fluids vs Electricity

Fluids: Resistance
Electricity: ______

A

Resistance

48
Q

Ohm’s Law

Units

A

Voltage = current x resistance

Ohms

49
Q

Veins

A

thin-walled collapsible

low pressure: partially filled with blood, partially expanded

low resistance vessels

50
Q

Veins during exercise

A

increases

changes from hourglass to oval than round

allows veins to accommodate a large volume increases with a very small increase in pressure

more round, resistance decreases, increasing outflow toward heart

51
Q

Hydrostatic Pressure

Unit

A

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

mmHg

52
Q

Hydrostatic Pressure accuracy measured at

A

level of the heart

too high, below the heart

too low, above the heart

53
Q

Hydrostatic Pressure- Supine

A

flat on your back

All parts of the body are at the same level as the heart and the pressure is zero everywhere

54
Q

Hydrostatic Pressure - Standing

Upright at heart level

A

pressure 0

measured pressure accurately represents true circulatory pressure

55
Q

Hydrostatic Pressure - Standing

below heart level

A

positive

measured pressure will be higher than the true circulatory pressure

56
Q

Hydrostatic Pressure - Standing

above heart level

A

negative

measured pressure will be lower than the true circulatory pressure

57
Q

Respiration affects venous flow for two reasons

A

Venous system is low pressure

Muscles responsible for respiration alter pressures in the thorax and the abdomen

58
Q

Breathing affects two venous flows

A

Venous flow to legs

Venous returns to heart, which comprises venous flow from the head, arms, and flow from the IVC to heart

59
Q

Diaphragm

A

Responsible for breathing

moves up and down, alternating the pressure in thorax and abdomen

60
Q

Inspiration

A

Diaphragm moves downward towards the abdomen

Thoracic pressure decreases

Adnominal pressure increases

Venous return to the hear increases

Venous flow in legs decreases

61
Q

Expiration

A

Diaphragm moves upward into thorax

Thoracic pressure increases

Abdominal pressure decreases

Venous return to the heart decreases

Venous flow in legs increases

Hemodynamic and Doppler (6 decks)

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