Doppler Principles

Question 1

Flow

Answer 1

go from one place to another in a steady stream

Question 2

velocity

Answer 2

the speed of something in a given direction

Question 3

Pulsatile flow

Answer 3

blood that flows with variable changes with the cardiac cycle in arterial circulation

Question 4

Phasic flow

Answer 4

when blood moves with a varying velocity, such as changes that occur with respiration (venous phase

Question 5

Laminar flow

Answer 5

• Layers of fluid are straight and parallel to each other, they slide over each other
• Highest flow speed at center of vessel
• Minimum or zero speed at walls
• Results in parabolic flow profile

Question 6

Plug flow

Answer 6

Flow with all fluid portions traveling with the SAME flow speed and direction (type of laminar flow)

Question 7

Parabolic flow

Answer 7

Laminar flow with a profile shape of a bullet; middle layers of blood travel faster than the layers at the sides of vessels

Question 8

Turbulent flow

Answer 8

• Random and chaotic flow pattern
• Particles move at different speeds in different directions
• Net result of forward flow is maintained

Question 9

Disturbed flow

Answer 9

• Layers are now altered from their straight flow
• Occurs at bifurcations and at stenoses
• The layers are still moving in the forward direction so is a form of laminar flow

Question 10

Bruit

Answer 10

Blowing, swishing sound indicating blood flow turbulence or atherosclerotic narrowing

Question 11

Thrill

Answer 11

a thrill is considered a palpable cardiac murmur. It feels like the throat of a purring cat and is abnormal. It signifies turbulent blood flow and accompanies loud murmurs. Absence doesn’t necessarily mean a murmur isn’t present

Question 12

Reynolds number

Answer 12

predicts wheather flow is laminar or tubulent

• laminar R# is 1,500.
• Turbulent flow Reynolds # is 2300
• critical reynolds number is 2000

Question 13

Energy Gradient

Answer 13

total fluid energy at one location differs from the total fluid energy at another location causing an

Question 14

Kinetic Energy

Answer 14

energy that a body possesses by virtue of being in motion.

Question 15

Pressure Energy

Answer 15

Pressure is defined as force per unit area

-the heart acts like a pump in the body

Question 16

Gravitational energy

Answer 16

potential energy associated with the gravitational field

Question 17

Viscous / viscosity

Answer 17

• defined as the friction existing between contiguous layers of fluid
• The resistance to flow offered by a fluid in motion
• Water has a low viscosity compared to molasses
• Viscosity of blood is 5 times that of water

Question 18

Frictional

Answer 18

of or produced by the action of one surface or object rubbing against or moving over another.

Question 19

Inertial

Answer 19

Mass is an object’s resistance to acceleration or flow

The resistance is called inertia

Greater mass = greater inertia

Question 20

Stenosis

Answer 20

Narrowing of a vessel lumen

Produces disturbed or turbulent flow

Question 21

Effects of a Stenosis

Answer 21

produces disturbed or turbulent flow

Question 22

Bernoulli’s Principle

Answer 22

• Explains that fluid moves against a pressure gradient from a point of low pressure to a point of high pressure
• Total fluid energy remains the same
• Pressure energy is converted to flow energy upon entrance to a stenosis
• As flow energy increases, pressure energy decreases (velocity goes up; pressure goes down)

Question 23

Pressure flow Relationships

Answer 23

Fluid in a tube flows in response to a pressure difference at both ends

Blood flows in response to pressure differences

With equal pressures at both ends, fluid will not flow

The pressure difference can be generated by a pump (such as the heart) or by gravity

The greater the pressure difference, the greater the flow rate

Question 24

Ohm’s Law

Answer 24

the voltage in a circuit equals the product of the current and the resistance

Question 25

Hydrostatic pressure

Answer 25

The pressure that the fluid exerts on the walls of its container.

Question 26

Expiration & inspiration

Answer 26

• inspiration- diaphragm contracts, expands, greater volume.
• expiration- passive, relaxation rib and sternum back in regular position

Question 27

external/ internal respiration

Answer 27

• external respiration- moving gases from outside the body into the lungs and then the blood.
• Internal respirtaiton- gas exchange between blood and tissues