Doppler Waveform Analysis Flashcards
Capabilities of doppler waveform analysis?
- help confirm diagnosis / approximate location of arterial occlusive disease
- Indicate severity
- Combine with doppler segmental pressures
Limitations of doppler waveform analysis?
- casts/bandages
- waveforms may be affected by ambient temperature
- Uncompensated congestive heart failure may result in dampened waveforms ***
- Unable to discriminate stenosis from occlusion
- tech dependent
Why do you do doppler waveforms with patient supine?
to decrease influence of hydrostatic pressure
Positioning for doppler waveform:
- supine
- hip rotated / knee slightly bent
- RLD/LLD
- prone
What is the doppler effect?
When a wave is reflected from a moving target, the frequency of the wave received is different (doppler shift) from the transmitted wave
Why does the doppler effect occur?
Relative to motion between the source and the receiver of the sound
(blood is moving target; transducer is stationary source)
What many crystals does continuous wave (CW) have?
two
The reflected frequency is higher/lower than the transmitted frequency depending on what?
direction of flow
What does an analog reader do?
employs a zero crossing frequency meter, to display the signals graphically on a strip chart recorder
Paper speed of an analog reader is:
25mm/sec
What does a zero crossing frequency meter count?
Each time the input signal crosses though zero (the baseline) within a time span
With zero crossing frequency meter, high frequency waves have how many oscillations?
many
lower frequencies have fewer
What does a zero crossing frequency meter machine estimate?
Frequencies present in reflected signal and displays them
Drawbacks of Analog:
- Noise
- Less sensitivity
- High velocities are underestimated
- Low velocities are oversestimated
What does spectral analysis display?
Individual frequencies displayed by Fast Fourier Transform (FFT) method
How is spectral analysis displayed? (x/y)
(X) Horizontal - displays time
(Y) Vertical - displays frequency shifts
What analysis is more commonly used during duplex evaluations?
Spectral
What probe is utilized for CW doppler?
8-10 MHz doppler probe
Upper extremity arteries are recorded from the following (top to bottom) bilaterally:
- Subclavian
- Axillary
- Brachial (at elbow)
- Radial (thumb side, at wrist)
- Ulnar (5th finger side, at wrist)
Lower extremity arteries are recorded from the following (top to bottom) bilaterally:
- Common femoral (CFA)
- Superficial femoral (SFA)
- Popliteal
- Posterior tibial (PTA) (medial malleolus)
- Dorsalis pedis (DPA) (top of foot)
- Peroneal (if necessary) (lateral malleolus)
The audible AND wave form qualities are observed, documented, and combined with what?
Doppler segmental pressures
What waveform has a rapid upslope, sharp peak, rapid down-stroke, flow reversal, and resumption of forward flow?
Triphasic
What are examples of triphasic flow?
UE, LE, arteries
What waveform has a rapid upslope, sharp peak, fairly rapid downstroke, flow reversal, no resumption of forward flow and can be considered normal in some patients?
Biphasic
What waveform has a slow upslope, rounded peak, slow down-stroke, and no reversal?
Monophasic
The dicrotic notch is also known as what?
Reflected wave
A monophasic/dampened (pulsatile) signal is often obtained where?
proximal to an obstruction
Well collateralized occlusions can appear similar to flow distal to what?
a stenosis
Vasoldilation of the distal vessels often occur with
Proximal obstruction
What will happen with a proximal occlusion or critical stenosis of the subclavian artery?
Will make the signal more monophasic
Strandness and Subner describe what?
arteriovenous shunts in the skin of fingertips that cause flow patterns in the hand to be tremendously variable
What is a normal doppler wave-form post exercise?
Pre-exercise wave form qualities are maintained and/ or augmented
What is an abnormal doppler wave-form post exercise?
Slow upstroke with more rounded peak, slow downstroke, no reverse component
Analog Doppler not capable of portraying velocities of less than:
6 cm/sec
How do you troubleshoot the machine if it says “60 cycle” noise on tracing?
Decrease gain; turn system off/on; increase filter; try another plug receptable.
How is the pulsatility Index (PI) calculated?
By dividing the peak-to-peak frequency difference (P1-P2) by the mean (average) frequency
An acceleration time of >133msec suggests what?
presence of proximal iliac disease
