ABI's Flashcards
What symptoms does a hemodynamically significant obstruction cause?
It causes symptoms in the LE of claudication, rest pain, gangrene, and ulceration.
What does a hemodynamically significant obstruction do to a waveform?
It causes a change in the waveform pulsatility distally due to arterioles opening and changing resistance.
What does a hemodynamically significant obstruction do to the pressure?
It causes the pressure to drop distally to the obstruction.
How does the ankle and brachial pressures compare?
Ankle pressures should be higher than the arm.
What does a decrease in the ankle pressure indicate?
It is an indication of an obstruction proximally causing a pressure gradient, therefore lowering the blood pressure at the ankles.
What do ABI’s measure?
They measure the pressure change distal to significant obstruction.
What do ABI’s indicate?
They indicate the presence of a hemodynamically significant obstruction as well as the severity of the decrease perfusion it has caused in the ankle level.
What does ABI stand for?
Ankle/Brachial Index
How do you calculate the ABI?
The systolic pressure at the ankle is measured and divided by the brachial artery systolic pressure.
What is the equation for ABI?
ABI= Ankle Pressure/ HIGHEST Brachial Pressure.
What position should ABI’s be measured in?
A patient MUST be measured in supine.
What size cuff should you use ?
10-12 cm wide.
Where should you obtain the best doppler signal?
DIstal to the cuff at the DP, PT, and brachial arteries.
Where should you measure the pressure in an ABI?
DP, PT and brachial arteries.
What happens if its not audible?
You move up to listen distal ATA, PTA, or PER A or move down to hear radial.
When taking a pressure measurement, what should you inflate the cuff to?
Inflate the cuff 20-30 mmHG over the last audible sound.
What should you listen to as you deflate the cuff 2-4 mmHg?
LIsten for the first sound, and note pressure, and continue to listen for continuation of pulses.
Will listening for the point the signal disappears on inflation yield an accurate pressure?
No!
When should you document the brachial pressures?
You should document brachial pressures when they are 20 mmHg different from each other, or do not sound multi-phasic, document the waveform.
What does a ABI interpret?
- Presence of disease
- Severity of disease
- Any changes
What is considered a normal ABI?
> .95 (asymptomatic)
What is considered a mild ABI?
.80-.95 (claudication)
What is considered a moderate ABI?
.50-.79 (claudication)
What is considered a severe ABI?
.30-.49 (possible rest pain)
What is considered a critical ABI?
Less than .30
If an ABI is >.50, what does this indicate?
It is likely there is only a single-level of obstruction.
What does it mean if an ABI is less than .50 (
It is likely there are multi-levels of obstruction.
What determines a follow up?
Changes in ABI’s from one study to the next.
What is a possible significant change?
> .15
What is a probable significant change?
> .20
What 3 things should you avoid when doing an ABI?
- Moving the probe while inflating the cuff.
- Pressing the DP too hard and compressing it with the probe.
- Not calming the patient.
What is the biggest limitation to an ABI?
Calcification.
Why is calcification a big limitation to an ABI?
If calcification is present in the arterial wall or in the plaque it is harder to compress the artery with the cuff. This results in a falsely elevated pressure that may miss disease or indicate that it is better than it truly is.
When should you suspect calcification is affecting the pressure?
When the ABI >1.35 and when the doppler and waveform disagree.
Which patients are susceptible to calcification?
Diabetics and renal failure patients.
What are some of the advantages of an ABI?
- Simple equipment
- Relatively easy to learn and execute
- Presence, severity and progression of disease in a simple test.
- Accurate
How can you improve the accuracy of an ABI?
to counteract the potential problems with each technique, doing BOTH ABI’s and DP and PT waveforms can improve accuracy.
TRUE OR FALSE: ABI’s with elevated pressures due to calcifications will have EXCELLENT pedal artery waveforms.
FALSE. They will have worse pedal artery waveforms.
