Chapter 4 Doppler waveform analysis

Question 1

Help confirm diagnosis/approx. location and severity of arterial occlusive disease

Combine with doppler segmental pressures

Answer 1

Capabilities

Question 2

Patients with casts or extensive bandages

Ambient temp can affect waveform quality

Congestive heart failure may result in dampened waveforms.

Cannot discriminate stenosis from occlusion

Technically dependent test

Answer 2

Limitations

Question 3

Supine with extremities at the same level as the heart to decrease influence of hydrostatic pressure

The patients hip is externally rotated, knee slightly bent (Reduce extrinsic compression)

Other positions: Rt/Lt lateral decubitus position, or prone

Answer 3

Patient positioning

Question 4

When wave is reflected from a moving target, the frequency of the wave received is different (doppler shift) from the transmitted wave.

This effect occurs with relative motion between the source and the receiver of the sound

Blood is moving target; transducer is stationary source

Answer 4

The doppler effect

Question 5

Two piezo-electric crystals: one constantly sending ultrasound, one constantly receiving reflected waves

The reflected frequency is higher/lower than the transmitted frequency depending on direction of flow

Answer 5

Continuous-wave (CW) Doppler is utilized

Question 6

Employs a zero crossing frequency meter

Answer 6

Analog

Question 7

Circuitry counts each time the input signal crosses through zero (the baseline) within a time span

Machine estimates frequencies present in reflected signal and displays them.

Answer 7

Zero crossing frequency meter

Question 8

Individual frequencies displayed by Fast Fourier Transform (FFT) method

Answer 8

Spectral analysis

Question 9

Timed displayed on what axis

Answer 9

horizontal axis (x)

Question 10

Frequency shifts displayed on the

Answer 10

Vertical axis (y)

Question 11

Acoustic gel applied; 8-10 MHz Doppler probe utilized

Answer 11

Technique

Question 12

Subclavian 
Axillary (axilla)
Brachial (at elbow- antecubital fossa)
Radial (thumb side)
Ulnar (5th finger side)

Answer 12

Upper extremities

Question 13

Common femoral  (CFA)
Superficial femoral (SFA)
Popliteal 
Posterior tibal (PTA) 
Dorsalis pedis (DPA)
Peroneal

Answer 13

Lower extremities

Question 14

Incorrect probe position 
Incorrect angle of incidence 
Inadequate amount of gel
Excessive pressure on the probe tip
Insufficient period of rest before testing (exercise messes it up vasodilation)

Answer 14

Potential sources of technical error

Question 15

Rapid upslope 
Sharp peak
Rapid downstroke
Flow reversal 
Resumption of forward flow
Examples: UE, LE, arteries

Answer 15

Triphasic

Question 16

Rapid upslope 
Sharp peak
Fairly rapid downstroke
Flow reversal 
No resumption of forward flow
Considered as normal in some patients

Answer 16

Biphasic

Question 17

Slow upslope
Rounded peak
Slow downstroke
No reversal

Answer 17

Monophasic

Question 18

Normal signals

Answer 18

Triphasic

Question 19

Abnormal signals

Answer 19

Biphasic, monophasic

Question 20

_____ ______ often occurs with proximal obstruction, reducing the pulsatility; causing the signals to have lower resistant (steady) flow quality

Answer 20

Vasodilatation of the distal vessels

Question 21

A high resistant, multiphasic flow

Answer 21

Subclavian

Question 22

Proximal occlusion will cause a more monophasic signal in the ______

Answer 22

Subclavian

Question 23

Post exercise

Pre-exercise wave form qualities are maintained and / or augmented. No reverse component

Answer 23

Normal

Question 24

Post exercise

More rounded peak, no reverse component

Answer 24

Abnormal

Question 25

Post exercise

Analog doppler not capable of portraying velocities of less than 6 cm/sec.
Pre-occlusive vessel (string sign).

Answer 25

Absent doppler signals