CW Doppler, ABI's, Segmental Pressures Flashcards
What is the purpose of all these exams? (CW Doppler, ABI’s, Segmental pressures)
- Look for the presence of disease - Check for the severity of the disease. - Locate the disease. - Observe the progression of the disease.
What does hemodynamically significant mean?
A blockage of 50% or greater.
What are the arterial physiological techniques used?
-CW Doppler -ABI’s -Segmental pressures -Volume pulse recording -Photoplethysmography
What does CW Doppler stand for?
Continuous wave.
What does the CW doppler act as?
A sender and receiver.
What does the CW doppler send?
It sends a continuous, not pulsed, ultrasound beam into the tissues.
What does it mean if the echo has a different frequency than what was sent?
Something is moving.
What is a doppler shift?
It is the difference in frequencies.
What is the doppler shifted frequency proportional to?
It is proportional to the velocity of the blood.
What can the doppler reveal?
It can tell if the blood is flowing towards the probe or away from the probe= direction of flow.
Changes in velocity and direction of flow are displayed in two ways by the CW doppler, what are they?
-Audible -Analog waveforms
Why type of doppler probe is usually used?
8-10 MHz Doppler probe
When should you use a lower frequency probe?
For heavier patients because their arteries are deeper.
Where do you want to obtain CW Doppler waveforms from?
-DPA -PTA -PER (rarely) -POP -FA -CFA
Where would you place the CW doppler probe?
You would place the probe where you would feel a pulse.
What is the optimal angle you want to aim for when trying to identify an arterial signal with the probe?
Keep a 30-45 ° angle to the skin.
How many waveforms do you want to obtain?
Obtain at least 3 waveforms.
How can you optimize the CW doppler signal?
-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.
Where should you look for a signal in the CFA?
Stay well above the bifurcation.
Where should you look for a signal in the SFA?
Artery is slightly medial to the DFA
Where should you look for a signal in the POP A?
Try mid to proximal; may need to sterr straight up and down rather than point to head.
Where should you look for a signal in the DPA?
Keep a very light touch near toe.
Where should you look for a signal in the PTA?
Angle doppler probe under the bone or check for a signal closer to the heel or proximally.
Where should you look for a signal in the PER A?
Anterior to the lateral malleolus.
How do you eliminate venous flow interference?
-Manually compress the limb proximal to the probe. -Have the patient take a deep breath and hold it. -Change the approach.
What should you do if you get a reverse waveform?
Do NOT invert the waveform.
What should you do if the waveform is too large for scale?
Turn down the scale, and note.
If you hear two vessels, where should you move?
Move proximally because you might be at a branch point or a bifurcation.
In a CW Doppler, as blood flows around the obstructions, there is a loss in what?
There is a loss of pulsatility in the velocity waveform along the path.
How are LE CW Doppler waveforms describes as?
- Triphasic
- Biphasic
- Monophasic
- Barely Pulsatile
- Non-pulsatile
Describe Triphasic:
Normal
- 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.
Describe Biphasic:
Mild to moderately abnormal.
- 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”
Describe Monophasic:
Severly abnormal reduction in perfusion.
- Broader, rounded peak with foward flow only.
- Reduced in amplitude, blunted.
- AKA “parvus tardus”= low (blunted) and late (slow upstroke)
- No inflection.
Describe Barely Pulsatile:
Critically reduced perfusion.
Describe non-pulsatile or absent doppler signal:
- could be occluded, calcified or poor angle.
- check proximal and distal to the typical point of insonation.
A CW Doppler can be used to distinguish the arterial segments of obstruction where?
- Aorto-iliac
- Femoral-popliteal
- infrapopliteal
How will all the waveforms below the site of obstruction look like?
Abnormal, even if there is no addisitional obstruction.
