The ABI or ankle brachial index is a non invasive tool to assess the presence of peripheral arterial disease. It assesses the severity of arterial insufficiency during ambulation.
How to measure ?
The ankle-brachial index ABI is measured by dividing the systolic pressure of the ankle by brachial systolic pressure.
What is PAD-
It is the reduction in the arterial blood flow to the limbs, which is apparent while ambulation.
Risk factors –
- History of tobacco use
Procedures to diagnose-
- Loose, comfortable clothes should be worn
- Avoid nicotine/ smoking
- Supported, comfortable position for the patient
- avoid limb movement during measurements.
- The supine position is the position of choice
Technique of ABI-
Measure the brachial pressure
- Place the cuff around the patient’s arm
- Now, use the hand doppler and press against the skin at the level of the brachial artery,
- record the highest measurement and repeat on the contralateral side.
Record the ankle pressure-
- Place the cuff around the lower leg
- Record the pressure at dorsalis pedis artery and posteriar tibial artery.
To calculate, divide the highest value of ankle systolic pressure by highest brachial pressure between the two arteries between both sides
Normal values- 0.90 and 1.30
Clinical Significance of ABI-
below 0.8 – may be suggestive of PAD
Below 0.7 – indicates severe PAD
Above the normal level- indicative of arterial calcification, however not confirmative
In normal healthy individuals, a reduced ABI may occur post exercising due to vasodilatation which returns to normal within 3 minutes.