Ankle-Brachial Pressure Index (ABPI)

The ankle brachial pressure index (ABPI) is an easily measured clinical parameter that is often used to assess the adequacy of blood flow to the lower limbs.

The patient should lie flat on a bed when having an ABPI measured. The systolic blood pressure in the brachial artery is measured using a stethoscope and sphygmomanometer. The systolic blood pressure at the ankle is then measured using a sphygmomanometer wrapped around the calf and a Doppler probe positioned over the posterior tibial or dorsalis pedis artery. Cuff pressure is inflated until blood flow to the foot is cut off. Flow is slowly re-established by deflating the cuff, and the pressure at which the first Doppler signal is obtained is noted.

After performing these tests, the observer will have two figures – the systolic blood pressures in the brachial artery and at the ankle. The ABPI is calculated simply by finding their ratio. In health, the ratio should be greater than or equal to 1. As the value decreases, symptoms and signs of arterial insufficiency to the lower limbs would be expected. Values lower than 0.5 may result in critical ischemia. ABPIs of lower than 0.2 can be associated with ulceration and gangrene.

ABPI	INTERPRETATION
>1	Normal
<0.5	At risk of critical ischemia
<0.2	At risk of ulceration and gangrene