Ankle Brachial Pressure Index

Daytonite, BSN, RN · May 23, 2006

The ABPI (Ankle Brachial Pressure Index) is calculated by taking blood pressure measurements at the ankle and in the upper arm of the patient. The systolic measurements that are obtained are then put into a ratio, or fraction, with the systolic pressure of the ankle as the numerator and the systolic pressure from the upper arm, or brachial artery, in the denominator. By converting this fraction into a decimal (divide the numerator by the denominator) you obtain a decimal number, the ABPI. A normal ABPI would fall between .95 to 1.2. In other words, the systolic pressure at both sites should be about the same. You start getting smaller and smaller decimals when the systolic blood pressure at the ankle is less than the systolic blood pressure in the brachial artery. This is a very strong indicator that peripheral artery disease (PAD) is present.

Now, the risk for the development of leg ulcers increases as the ABPI gets smaller. So, someone with an ABPI of .4 is at a real risk of any tissue injury in the lower extremity turning into a stasis ulcer. The information that I have on this is that problems seldom develop with ABPI's of .8 or above. Between .4 and .8 there is a moderate risk, but PAD is present. The patient may have leg pain and definitely foot care needs to be instituted and the feet and lower extremities examined frequently and protected from injury. Below .4 indicates a high risk for stasis ulcer formation accompanied by infection. Amputation is a complication of stasis ulcers that do not respond to treatment which is likely to occur if there has been significant progression of the PAD.

I was just wondering how does it work if to say: Brachial Pulse might be 0.9 and if ankle pulse is for example 0.7 then what would the Ankle Brachial Pressure Index be???

Are these dopler readings? Because they certainly aren't blood pressure readings. Assuming they are dopler readings, you merely place the ankle figure (.7) over the brachial figure (.9) which would result in .7777 rounded off to .8 which is a low risk. However, you see that the ankle figure is lower than the brachial figure which indicates that there is most likely some PAD already occurring in the patient although perhaps not significant enough to produce bothersome symptoms as of yet.

AussieKylie · May 23, 2006

Thank you once again DaytoNite

I understand fully.

Thanking you heaps :balloons: