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RVT Review > Chapter 4 > Flashcards

Chapter 4 Flashcards

1
Q

what are some capabilities for doppler waveform analysis?

A

a. help confirm diagnosis/ approx location of arterial occlusive disease
b. indicate severity of the occlusive process
c. combined with doppler segmental pressures

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2
Q

What are some limitations of doppler waveform analysis?

A

a. patients with casts or extensive bandages
b. waveforms may be affected by ambient temp
c. uncompensated CHF may result in dampened waveforms
d. unable to discriminate stenosis from occlusion
e. technically dependent test

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3
Q

what is the patient positioning?

A

supine with extremities at the same level as the heart. to decrease the influence of HP
the patients hip is externally rotated, knee slightly bent
other positions: RLD LLD or prone

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4
Q

what is the doppler effect?

A

when a wave is reflected from a moving target, the freq of the wave received is different (doppler shift) from the transmitted wave

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5
Q

why does the doppler effect occur?

A

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

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6
Q

what is considered a moving target?

A

blood

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7
Q

what is considered a stationary source?

A

the transducer

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8
Q

describe CW doppler

A

the reflected freq is higher/lower than the transmitted freq, depending on direction of flow

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9
Q

what is a type of doppler velocimetry?

A

analog

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10
Q

what is an analog?

A

employs a zero crossing freq meter, to display the signals graphically on a strip chart recorder

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11
Q

what are zero crossing freq meters?

A
  • circuitry counts each time the input signal crosses through zero (the baseline) within a time span
  • high freq waves have many oscillations ; low freq waves have few
  • direction of blood flow varies during the cardiac cycle
  • machine estimates freq present in reflected signal and displays them
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12
Q

what are some drawbacks of analog recordings?

A

noise, less sensitivity, high velocities are underestimated, low velocities are overestimated

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13
Q

what is spectral analysis?

A

individual frqs displayed by FFT method

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14
Q

when is spectral analysis more commonly used?

A

duplex evaluation

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15
Q

on the graph what is displayed on the x and y axis on a spectral analysis?

A

x=time

y=freq shifts / velocity

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16
Q

T/F spectral analysis has many drawbacks like the analog

A

false

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17
Q

what transducer is used for spectral analysis?

A

8-10 MHz

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18
Q

which arteries do you evaluate with a duplex study for UE?

A 
subclav
axillary (axilla)
brach (antecub fossa)/ elbow
radial  (wrist, thumb side)
ulnar (wrist, 5th finger side)
19
Q

which arteries do you evaluate with a duplex study for LE?

A 
CFA
SFA
pop
PTA
DPA
peroneal if necessary at lateral malleolus
20
Q

what are some potential sources of technical error?

A 
improper probe position 
inadvertent probe motion 
incorrect angle of incidence 
inadequate amount of gel 
excessive pressure on the probe tip 
insufficient period of rest before testing
21
Q

What are more signals considered?

A

triphasic

22
Q

what are some characteristics of a triphasic waveform?

A 
rapid upslope 
sharp peak 
rapid down stoke 
flow reversal 
resumption of forward flow
23
Q

what vessels are mostly triphasic?

A

UE, LE

24
Q

what are come characteristics of a biphasic waveform?

A 
rapid upslope
sharp peak 
fairly rapid downstroke 
flow reversal 
no resumption of forward flow
also considered normal in some patients
25
Q

what are some characteristics of a monophasic waveform?

A

slow upslope
rounded peak
slow down stroke
no reversal

26
Q

where is a common place to see a monophasic/dampened (pulsatile) signal?

A

is obtained proximal to an obstruction

no diastolic flow

27
Q

well collateralized occlusions can appear similar to flow ___ to a stenosis

A

distal

28
Q

what does vasodilation of the distal vessels occur with?

A

proximal obstruction

it reduces the pulsatility, causing the signals to have lower resistant steady flow quality

29
Q

what will the sub a waveform look like?

A

high resistant, multiphasic flow

30
Q

what will the sub a waveform look like with a proximal obstruction?

A

monophasic

31
Q

what are normal pre excerise waveforms?

A

no reverse component. usually just pressured obtained post exercise

32
Q

what will the waveform look like in a abnormal patient post exercise?

A

slow upstroke with more rounded peak, slow downstroke, no reverse component

33
Q

what do absent doppler signals suggest?

A

occlusion or a pre occlusive vessel (string sign).

34
Q

what is the lowest velocity that an analog doppler can display?

A

less than 6cm/s

35
Q

what should you do when the recorder stylus not recording?

A

check that proper test selection and/or probe type has been made

36
Q

what should you do when the 60 cycle noise on tracing?

A

decrease gain, turn system off/on, increase filter, try another plug receptacle

37
Q

what should you do when the recording stylus stuck at lower or upper portion of tracing?

A

activate re set control to recenter

38
Q

how do you calculate pulsatility index (PI)?

A

divide peak to peak frq difference (P1-P2_ by the mean average freq

39
Q

what does pulsatility index help defferentiate?

A

inflow from outflow disease e.g aortoiliac from femoral disease

40
Q

what does acceleration time help differentiate?

A

helps to differnetiate inflow (aorto-iliac) disease from outflow (s-femoral) disease

41
Q

what principle does acceleration time based on?

A

that proximal disease obstruction results in a slowing of the time interval between the onset of systole to the point of max peak

42
Q

slowing of time= what?

A

proximal obstruction

43
Q

what acceleration time does it suggest a proximal iliac disease?

A

> 133msec

RVT Review (30 decks)

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