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Protocols for: Performing Ankle-Brachial IndexesPrior
to applying compression to lower extremities, it is necessary to assess lower
extremity blood flow. Doppler ultrasound can provide valuable data on the status
of the arterial and venous blood flow of vascular-compromised patients. The
process described here focuses on arterial blood flow. A commonly used test to
evaluate lower extremity arterial blood flow is called the ankle-brachial index
or ABI. The Doppler ultrasound
device transmits a 2-10 MHz signal into the artery being evaluated. This allows
for the assessment of three sounds - monophasic, biphasic, and triphasic. A
triphasic sound is indicative of a healthy artery. Biphasic sounds are safe and
tend to be the most common. Monophasic sounds indicate occlusion. ABI Protocol: 1.
Patient should be supine for 20 - 30 minutes to establish a resting blood
pressure 2.
Obtain the systolic blood pressure of the brachial artery 3.
Find the systolic pressure of the lower extremity by placing the pressure
cuff around the ankle with the Doppler probe placed over the posterior tibial or
dorsalis pedis artery 4.
Divide the lower extremity
pressure by the upper extremity pressure to obtain ABI reading.
It
is safe to apply compression to the lower extremity if the ABI is 0.85 or
greater. Patients with ABIs of less than 0.80 should be evaluated for arterial
compromise before compression is applied.
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