Doppler Waveforms

What is a normal peripheral arterial doppler waveform?

• clear spectral window

• triphasic flow

• high resistance

What transducer is typically used to exam dopplers?

continuous wave (CW)

Doppler waveforms are recorded from:

• common femoral

• superficial femoral

• popliteal

• posterior tibial

• dorsalis pedis

An approximately ____ _____ angle to the skin should be used

45 degree

Interpretation of Doppler waveforms is limited to their?

their shape

triphasic

biphasic- bidirectional

biphasic- unidirectional

monophasic- moderate/severe

monophasic- severe/critical

Normal Doppler waveforms are __________ and bi to __________

bidirectional; triphasic 

Flow reversal relates to

greater resistance to flow

PAOD reduced flow energy _______ to the lesion

distal

PAOD:

• results in reduction of peripheral resistance 

• reduces amount of flow reversal

• volume flow is maintained in this way until PAOD reaches critical stage

• arteriolar bed can no longer dilate to increase blood flow

• patient experiences rest pain

What does PAOD stand for?

Peripheral Arterial Occlusive DIsease

Segmental Doppler is blood pressure at?

upper thigh, lower thigh, and calf

For a segmental Doppler pressures allow how many minutes for a rest period before examination for patients BP to stabilize?

15 minute rest period

What can you do during the patient’s rest period?

the patient’s history can be obtained

What history should we document?

risk factors, current severity and location of symptoms, and previous history of arterial interventions, including arterial operations

DO NOT place cuffs on areas of?

graft placement

Cuff Size:

width should be 20% wider than the diameter of underlying limb

-the length should be 2 times of width of the cuff

cuff too narrow=

falsely elevated pressure

cuff too wide=

falsely lower pressure

For ankle brachial indexes (ABIs)

upper arm

ankle

-ABI is a very common one they use

For multilevel lower extremity pressures

upper arm

thigh

calf 

ankles

Doppler Signal is obtained ______ to the cuff

distal

-usually obtained at PTA and DPA
-care must be taken not to compress these vessels

Once Doppler signal is obtained, cuff is inflated to register systolic pressure:

cuff should be inflated 20-30 mmHG above point where signal disappears

-cuff should be deflated at a rate of about 3 mmHg

What do you inflate to?

65 mmHg

done bilaterally 

What is pressure index?

all pressures are divided by the highest brachial pressure and expressed as a ratio

Although PIs are reported at each level that pressures are obtained, the most commonly used are?

ABIs

What does ABI stand for?

ankle brachial index

What is ABI?

ratio of doppler systolic pressures at the brachial level to those at the ankle

-indicates the overall severity of PAOD

How is ABI calculated?

by dividing the highest systolic ankle pressure by the highest brachial systolic pressures

-bilateral brachial, posterior tibial, and dorsalis pedis artery pressures should all be documented

What is the normal ABI?

about 1.0

A change of 0.15 between repeat studies is considered?

significant

Lower ABI values correspond to?

worsening PAOD

Excessively high ABI values typically correspond to?

calcified arteries

-systolic pressure is invalid when the underlying artery is calcified and incompressible

-interpretation then relies on waveform analysis

ABI indicates overall severity of PAOD but not

necessarily the site

What can add additional information about disease location?

segmental limb pressures

Volume plethysmography waveforms can also be obtained to aid in?

interpretation

Pressures are taken at multiple sites down the 

leg

Pressure differences are noted between locations and can indicate

specific level of disease

3 cuff method:

one large cuff on thigh, one cuff around calf just below the knee, and one cuff at the ankle

4 cuff method:

two smaller cuffs on thigh (high thigh and above knee), one at calf, and one at ankle

-allows ability to further define level of disease by separating iliofemoral disease from superficial femoral artery disease

Doppler signal is obtained at the

ankle

Pressures are obtained from

the ankle level followed by the calf then thigh levels

The PTA or DPA with the highest pressure is used for

pressure measurement up the limb

Systolic pressures usually ________ as blood flows distally in the lower extremity 

increase

Any reduction in distal pressure should be ______ mmHg between adjacent segments

<20

pressure drop >20 mmHg indicates presence of proximal obstruction

Width of thigh cuff changes interpretation:

-single large thigh cuff results in a thigh pressure equal to the brachial pressure

-use of narrower high thigh cuff results in higher thigh pressure (about 30 mmHg above brachial pressure)

Reasons for Underestimation:

-not able to detect very mild disease

-proximal disease may mask distal disease

-calcified vessels may falsely elevate the pressures recorded