CW Doppler, ABI's, Segmental Pressures

Question 1

What is the purpose of all these exams? (CW Doppler, ABI’s, Segmental pressures)

Answer 1

• Look for the presence of disease - Check for the severity of the disease. - Locate the disease. - Observe the progression of the disease.

Question 2

What does hemodynamically significant mean?

Answer 2

A blockage of 50% or greater.

Question 3

What are the arterial physiological techniques used?

Answer 3

-CW Doppler -ABI’s -Segmental pressures -Volume pulse recording -Photoplethysmography

Question 4

What does CW Doppler stand for?

Answer 4

Continuous wave.

Question 5

What does the CW doppler act as?

Answer 5

A sender and receiver.

Question 6

What does the CW doppler send?

Answer 6

It sends a continuous, not pulsed, ultrasound beam into the tissues.

Question 7

What does it mean if the echo has a different frequency than what was sent?

Answer 7

Something is moving.

Question 8

What is a doppler shift?

Answer 8

It is the difference in frequencies.

Question 9

What is the doppler shifted frequency proportional to?

Answer 9

It is proportional to the velocity of the blood.

Question 10

What can the doppler reveal?

Answer 10

It can tell if the blood is flowing towards the probe or away from the probe= direction of flow.

Question 11

Changes in velocity and direction of flow are displayed in two ways by the CW doppler, what are they?

Answer 11

-Audible -Analog waveforms

Question 12

Why type of doppler probe is usually used?

Answer 12

8-10 MHz Doppler probe

Question 13

When should you use a lower frequency probe?

Answer 13

For heavier patients because their arteries are deeper.

Question 14

Where do you want to obtain CW Doppler waveforms from?

Answer 14

-DPA -PTA -PER (rarely) -POP -FA -CFA

Question 15

Where would you place the CW doppler probe?

Answer 15

You would place the probe where you would feel a pulse.

Question 16

What is the optimal angle you want to aim for when trying to identify an arterial signal with the probe?

Answer 16

Keep a 30-45 ° angle to the skin.

Question 17

How many waveforms do you want to obtain?

Answer 17

Obtain at least 3 waveforms.

Question 18

How can you optimize the CW doppler signal?

Answer 18

-Adjust angle to the skin -Rest hand if you are not steady but use a glove if you rest it on the patient -Use volume control.

Question 19

Where should you look for a signal in the CFA?

Answer 19

Stay well above the bifurcation.

Question 20

Where should you look for a signal in the SFA?

Answer 20

Artery is slightly medial to the DFA

Question 21

Where should you look for a signal in the POP A?

Answer 21

Try mid to proximal; may need to sterr straight up and down rather than point to head.

Question 22

Where should you look for a signal in the DPA?

Answer 22

Keep a very light touch near toe.

Question 23

Where should you look for a signal in the PTA?

Answer 23

Angle doppler probe under the bone or check for a signal closer to the heel or proximally.

Question 24

Where should you look for a signal in the PER A?

Answer 24

Anterior to the lateral malleolus.

Question 25

How do you eliminate venous flow interference?

Answer 25

-Manually compress the limb proximal to the probe. -Have the patient take a deep breath and hold it. -Change the approach.

Question 26

What should you do if you get a reverse waveform?

Answer 26

Do NOT invert the waveform.

Question 27

What should you do if the waveform is too large for scale?

Answer 27

Turn down the scale, and note.

Question 28

If you hear two vessels, where should you move?

Answer 28

Move proximally because you might be at a branch point or a bifurcation.

Question 29

In a CW Doppler, as blood flows around the obstructions, there is a loss in what?

Answer 29

There is a loss of pulsatility in the velocity waveform along the path.

Question 30

How are LE CW Doppler waveforms describes as?

Answer 30

• Triphasic
• Biphasic
• Monophasic
• Barely Pulsatile
• Non-pulsatile

Question 31

Describe Triphasic:

Normal

Answer 31

• Rapid upstroke with a sharp peak.
• Rapid downstroke with a short peak below the baseline, then a smaller peak above.
• The large velcoity peak is produced during cardiac systole as the large bolus of bloos is propelled from the heart to the arteries.
• A brief phase of flow reversal occurs in diastole.
• Small peak of flow from late diastole–result of the artery elasticity expanding the artery walls again.

Question 32

Describe Biphasic:

Mild to moderately abnormal.

Answer 32

• Reduction in perfusion.
• Biphasic waveforms occur distal to obstructions.
• Quick upstrokes with narrow peak but no reversed flow in late systole, early diastole.
• Flow foward “with inflection”

Question 33

Describe Monophasic:

Severly abnormal reduction in perfusion.

Answer 33

• Broader, rounded peak with foward flow only.
• Reduced in amplitude, blunted.
• AKA “parvus tardus”= low (blunted) and late (slow upstroke)
• No inflection.

Question 34

Describe Barely Pulsatile:

Answer 34

Critically reduced perfusion.

Question 35

Describe non-pulsatile or absent doppler signal:

Answer 35

• could be occluded, calcified or poor angle.
• check proximal and distal to the typical point of insonation.

Question 36

A CW Doppler can be used to distinguish the arterial segments of obstruction where?

Answer 36

• Aorto-iliac
• Femoral-popliteal
• infrapopliteal

Question 37

How will all the waveforms below the site of obstruction look like?

Answer 37

Abnormal, even if there is no addisitional obstruction.