Physical Examination: Ankle Brachial Index (ABI)
|
|---|
- A tool for assessing the presence of peripheral artery disease (PAD)
- The ABI has a sensitivity 95% and a specificity 99%
- Patients who are unable to remain supine for the exam
- Patients in whom the occlusion from the blood pressure cuff may worsen the extremity injury
- An appropriately sized blood pressure cuff for the upper and lower extremities with a working sphygmomanometer
- A Doppler device for detecting flow
- Ultrasound transmission gel
- The patient should rest supine, with arms and legs at the level of the heart, on a exam table in a warm room for at least 10 minutes before testing
- Choose an appropriate size blood pressure cuff for both arms and ankles (cuff width should be, at a minimum, 20% greater than the diameter of the extremity)
- Place blood pressure cuffs on the arm and ankle on the side to be measured first
- The ankle cuff should go on the leg between the malleolus and the calf
- Apply ultrasound gel over brachial, dorsalis pedis, and posterior tibial arteries
- Measure systolic pressure in arms
- Use vascular Doppler to locate brachial pulse (medial side of the antecubital fossa)
- Inflate cuff 20 mm Hg above last audible pulse
- Deflate cuff slowly and record pressure at which pulse becomes audible
- Obtain 2 measures in each arm and record the average as the brachial pressure in that arm
- Measure systolic pressure in ankles
- Use vascular Doppler to locate dorsalis pedis (DP) pulse (dorsum of the foot between the proximal section of the first and second metatarsals)
- Inflate cuff 20 mm Hg above last audible pulse
- Deflate cuff slowly and record pressure at which pulse becomes audible
- Obtain 2 measures in each ankle and record the average as the dorsalis pedis pressure in that leg
- Repeat step 6 for posterior tibial (PT) arteries (just dorsal and inferior to the medial malleolus)
- Calculate ABI (see next section)
- Right ABI = highest right average ankle pressure (DP or PT) divided by highest average arm pressure (right or left)
- Left ABI = highest left average ankle pressure (DP or PT) divided by highest average arm pressure (right or left)
- > 1.30 = Noncompressible, severely calcified vessel
- >0.90 (range of 0.90 to 1.30) = normal lower extremity blood flow
- <0.89 to >0.60 = Mild PAD
- <0.59 to >0.40 = Moderate PAD (sufficient to cause claudication)
- <0.39 = Severe PAD (sufficient to cause resting pain or gangrene)
- The difference between the 2 readings for each artery should be less than 10 mm Hg
- Patients with diabetes may have extensive medial layer calcinosis, rendering the vessel resistant to compression by the pneumatic cuff
- If done properly, the ABI has a sensitivity 95% and a specificity 99%
- Bickley LS et al. Bates' Guide to Physical Examination and History Taking. 11th ed. Philadelphia, PA: Lippincott Williams & Wilkins. 2013; 516.
- Hiatt WR. Medical treatment of peripheral arterial disease and claudication. N Engl J Med. 2001;344(21):1608-21.
- McDermott MM et al. The ankle-brachial index is associated with leg function and physical activity: the walking and leg circulation study. Ann Intern Med. 2002;136:873-883.
Definition
Contraindications
Equipment
Technique
How to Calculate Ankle Brachial Index (ABI)
Interpretation of ABI Results
Pearls
References
MESH Terms & Keywords
|
|---|
|
