Study guide test 3

Question 1

What is the movement of fluid from one location to another?

Answer 1

velocity

Question 2

Fluid moving with a variable velocity, that accelerates and decelerates; what is it?

Answer 2

pulsatile flow

Question 3

What is fluid moving from one location to another that accelerates and decelerates from respiration called?

Answer 3

phasic flow

Question 4

What type of flow pattern will be seen with normal physiological states?

Answer 4

laminar flow

Question 5

Chaotic flow with many directions and speeds, whay type of flow is this?

Answer 5

turbulent flow

Question 6

Frictional loss occurs when one object rubs against another. Blood sliding across vessel walls would be considered what?

Answer 6

frictional loss

Question 7

Know the Reynolds numbers

Answer 7

< 1500= laminar

1500-2000= ????

>2000= turbulent

Question 8

What are the effects of stenosis?

Answer 8

change in flow direction

increased velocity as vessel narrows

turbulence downstream from the stenosis

pressure gradient across the stenosis

loss of pulsatility

Question 9

What is hydrostatic pressure?

Answer 9

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

Question 10

Hydrostatic pressure in a supine patient with a blod pressure of 140mmHg

Answer 10

all measurement sites= 0mmHg

Question 11

Hydrostatic pressure while standing upright in a patient with a blood pressure of 140mmHg:

Answer 11

ankle: level-far below heart level, hydrostatic pressure-100mmHg, measured pressure-240mmHg
knee: level-somewhat below heart, hydrostatic pressure-75mmHg, measured pressure-215mmHg
waist: level-slightly below heart, hydrostatic pressure-50mmHg, measured pressure-190mmHg

mid chest: level-heart level, hydrostatic pressure-0mmHg, measured pressure-140mmHg

top of head: level-above heart, hydrostatic presure–30mmHg, measured pressure-110mmHg

Question 12

What does the Doppler shift provide information about?

Answer 12

measures the velocity of blood in the circulation

Question 13

What is a positive Doppler shift?

Answer 13

blood moves towards transducer (arteries)

Question 14

What is a negative Doppler shift?

Answer 14

blood moves away from transducer (veins)

Question 15

What is the typical range of a Doppler shift?

Answer 15

20Hz to 20,000Hz (range of audible sound)

Question 16

What is the phenomenon where high velocities appear as negative?

Answer 16

aliasing

Question 17

When the sample volume is deep, the PRF is what? Nyquist limit?

Answer 17

low

Question 18

What are the 5 ways to eliminate aliasing?

Answer 18

adjust the scale to its maximum-increases Nyquist limit

select a new ultrasonic view with a shallower sample volume-increases Nyquist limit

select a lower frequency transducer-decreases Doppler shift

use baseline shift-aliasing remains but display more appealing

use continuous wave Doppler-never aliases, but range ambiguity

Question 19

Know about large and small sample volumes. Which one will fill in on Doppler?

Answer 19

large spectral broading

Question 20

What do the X and Y axis stand for on the Doppler spectrum?

Answer 20

X=time

Y=shift or velocity

Question 21

What 2 things are related to Doppler spectrum?

Answer 21

amplitude of the reflected signal

number of blood cells creating the reflection

Question 22

When we look at our Doppler Spectrums and we see our wave form, if you have a higher waveform, is a higher freq or lower freq being used?

Answer 22

higher frequency

Question 23

What is Doppler shift inversely related to?

Answer 23

propagation speed

Question 24

What is the basic Doppler system that simply identifies blood flow by the pressence of the frequency shift?

Question 25

What is the Doppler effect?

Answer 25

frequency shift

Question 26

What is the difference betwen speed and velocity?

Answer 26

speed measures distance velocity measures magnitude and direction

Question 27

Know about angles with Doppler:

Answer 27

when the angle between the direction of motion and sound is 0º or 180º, flow is parallel to the sound beam the measured and true velocities are equal: Cosine 0º=1 (flow toward transducer), Cosine 180º=-1 (flow away from transducer) Cosine 90º=0 (perpindicular/normal incidence can not measure Doppler shifts and velocities

Question 28

What's a primary advantage for pulsed wave Doppler?

Answer 28

range resolution (being able to select the exact location where velocities are measured)

Question 29

What's the primary advantage to continuous wave Doppler?

Answer 29

ability to accurately measure very high velocities

Question 30

What kind of processing does bidirectional Doppler use?

Answer 30

phase quadrature

Question 31

Fast Fourier Transform (FFT) is used in what type of process?

Answer 31

used to process both pulsed and continuous wave Doppler signals

Question 32

What type of velocities does color flow measure?

Answer 32

negative and positive shifts slower and faster velocities laminar and turbulent flow

Question 33

What is autocorrelation?

Answer 33

a digital technique used to analyze color flow Doppler

Question 34

What are the personal limitations to color flow imaging?

Answer 34

more time needed to aquire data reduced frame rate decreased temporal resolution

Question 35

What is the area of interrogation in a Pulsed Doppler jam called?

Answer 35

sample volume

Question 36

What are the advantages and disadvantages of large Doppler packets?

Answer 36

Advantages: more accurate velocity measurement, increased sensitivity to low flow Disadvantages: more time needed to aquire data, reduced frame rate, decreased temporal resolution

Question 37

How do you measure low flow rates?

Question 38

Know about inspiration:

Answer 38

diaphragm moves upward toward abdomen thoracic pressure decreases abdominal pressure increases venous return to the heart increases venous flow in legs decreases

Question 39

Know about expiration:

Answer 39

diaphragm moves upward into thorax thoracic pressure increases abdominal pressure decreases venous return to the heart decreases venous flow in legs increases

Question 40

When venous pressure is low, what is the volume of pressure in the veins?

Answer 40

low

Question 41

What happens to the shape of veins when the venous pressure increases?

Answer 41

becomes more circular