Photoplethysmography & Ankle Brachial Index (ABI)

An Ankle Brachial Index is a test that can indicate the presence of’ furring’ in the leg arteries, a common cause of poor circulation to the feet.

Systolic blood pressures are taken in the arms and divided by the pressures recorded from the ankle. Healthy leg arteries would exhibit little difference between the arm and ankle pressures (1.0 – 1.3).Readings between 0.8-0.9 would indicate modest PAD, readings between 0.6 -0.8 would indicate more established PAD and readings below 0.6 would indicate significant and probably symptomatic PAD.

The test can be undertaken manually or by using a Photoplethysmography (PPG) machine. PPG provides more reliable results, and offers the practitioner the opportunity of viewing a waveform of blood flow via a PPG sensor attached to the tip of a toe.

ABI readings of above 1.3 would indicate hardening of the leg arteries and therefore a Toe Brachial Index (TBI) is undertaken instead. Hardening of leg arteries produce high ABI readings since the arteries require more pressure to compress and therefore the toe arteries are used as an alternative (arteries in toes do not usually become hardened).




This equipment is used regularly at this practice and is the main focus of our Diabetic Vascular Testing. It is exceptionally rare for a podiatry practice to have access to such equipment and to undertake such testing.






The test is useful in identifying Asymptomatic PAD in patients considered to be at high risk, particularly Diabetics.

Where high risk patients are identified as having very low ABI readings and are symptomatic (where the poor circulation causes symptoms that affect the patient adversely) then we would normally refer to a vascular specialist via a GP for their assessment.

This test provides the patient with the ‘Gold Standard’ in community based peripheral vascular testing and in line with diabetic protocol we encourage our diabetic patients to undertake this test annually. The test takes approximately 30-40 mins. A copy of the test results are given to the patient who are then advised to present the results to their Diabetic Nurse at their next annual Diabetic ‘check up’.