Improving Quality of Care Based on CMS Guidelines 23

How to Measure Ankle Brachial Index

by Jackie Todd MBA, BS, RN, CWCN, DAPWCA

Ankle Brachial Index (ABI) is a screening tool for significant arterial flow

problems to the extremities. It compares blood flow pressure in the lower leg to

blood flow pressure in the upper arm. Its purpose is to help identify patients for

whom compression therapy would be appropriate. Please note that ABI screening

may not be accurate in patients with diabetes whose veins are calcified.

Camera not included.

24 Healthy Skin

1 Have the patient remove their shoes and socks and lie in the supine position for at least 10 minutes prior to obtaining blood pressure readings.

2 Apply blood pressure cuff snugly to the upper arm with the lower edge of the cuff one inch above the antecubital space. An appropriately sized cuff for the arm will usu-ally be appropriately sized for the ankle. In the event that arm and ankle sizes are markedly different, choose cuff sizes that are appropriate for each site.

3 Apply an adequate amount of Doppler gel to the antecubital area.

4 Turn the Doppler on and place the probe on the antecubital space at approximately a 60-degree angle to the skin surface. Move the probe around until the clearest arterial pulse is heard, and keep the probe in that position while taking the blood pressure.

5 Inflate the blood pressure cuff to approxi-mately 20 mmHg above the numerical reading where the pulse sounds cease.

6 Deflate the cuff at a rate of 2 mmHg per second until the first arterial pulse sound is heard. Once the number is determined, deflate the cuff completely and record this sys-tolic pressure. Remove the gel from the patient’s skin.

7 Apply the same blood pressure cuff to the ankle on the same side of the body.

8 Palpate the area around the medial malleo-lus to find the posterior tibial arterial pulse.

ABI Measurement Steps

Dorsalis pedis

Posterior tibial pulse

Use the ABI Worksheet on page 26 to record your results.

Improving Quality of Care Based on CMS Guidelines 25

Follow the manufacturer’s instructions specific to the Doppler probe you are using.

Be sure to use enough gel.

Use a cuff size that is right for both the arms and ankles of the patient.

Be sure you’re centered on the pulse when you take the reading; if you are off to the side the reading will be low.

Be aware that patients with diabetes commonly have calcified vessels and abnormally high ABIs.

In a small percentage of patients, one of the ankle pressures will be undetectable. Use the detectable pressure for calculating the ABI.

Don’t be discouraged if measuring the ABI seems slow or clumsy at first. Like any procedure the ABI becomes easier to do with practice.

The following is a guide to interpreting the results of the ABI.

>1.4 Indicates noncompressible vessels > 1.0 Normal < 0.9 LEAD < 0.6 to 0.8 Borderline <0.5 Severe ischemia

*Note: In instances where only one extremity can be accessed, use the available systolic ankle/brachial reading for calculating ABI.

Source: Wound, Ostomy and Continence Nursing Society.

Ankle Brachial Index: Best Practice for Clinicians

HelpfulHints

Interpretation of Findings

9 If the pulse is palpable, apply Doppler gel to the area. If there is no palpable pulse, apply the Doppler gel, turn on the Doppler device and use the probe to find the pulse. Move it around the general area until the clearest arterial sound is heard. Keep the probe in that position and take the blood pressure by inflating the cuff and fol-lowing the procedure as before when obtaining the arm pressure readings. Record the reading.

10 Doppler device obtain the systolic reading for the pos-terior tibial reading.

11 Repeat the process for other side of body—brachial, posterior tibial and dorsalis pedis.

12 To determine the ABI, divide the higher of the two ankle pressures by the higher of the two brachial pressures. If only one ankle pressure could be obtained, use that one.

Ankle Pressure Brachial Pressure

= ABI

26 Healthy Skin

ABI WorksheetABI = Ankle brachial indexDP = Dorsalis PedisPT = posterior tibial

Highest Right Ankle Pressure Highest Right Brachial Pressure

Right ABI = Ratio ofHigher of the Right Ankle pressures (DP OR PT)

Higher Arm Pressure (right or left arm)

left ABI = Ratio ofHigher of the left Ankle pressures (DP OR PT)

Higher Arm Pressure (right or left arm)

mmHg

mmHgmmHg

mmHgmmHg

mHg mHg

mHg mHg

DP DP

PT PT

m m

m m

mmHg

RIGHT ARM BRACHIAl SYSTOlIC

RIGHT ANKlE SYSTOlIC PRESSURE

lEFT ARM BRACHIAl SYSTOlIC

lEFT ANKlE SYSTOlIC PRESSURE

Highest left Ankle Pressure Highest left Brachial Pressure

= ABI = ABI

=

=