The ankle-arm pressure index (also known as the Ankle/Brachial Index or ABI) compares the systolic blood pressure of the ankle to that of the arm (brachial).

These measurements are useful in the assessment, follow-up and treatment of patients with peripheral vascular disease (PVD). ABI's provide an objective baseline to follow the progression of the disease process and evaluate the effectiveness of the treatment plan.

Significant changes in arterial systolic pressure between sites indicate reduced blood flow caused by obstruction of blood vessels. The effects of obstructions can be emphasized by increasing blood flow, either by exercise testing or by inducing reactive hyperemia with an occlusive cuff.

Patients, such as diabetics, with calcified vessels may show falsely elevated ankle pressures. In this case, pressure measurements can be made on the foot or toes by Photo Plethysmography (PPG) for more accurate results.

Diagnostic information is obtained both from the waveform of the arterial flow when displayed on a chart recorder and from using the PPG sensor to determine the blood pressure in the digit.

To detect pressures a Doppler or PPG sensor is used. Pulse waveforms are recorded on a chart recorder.