Validation of a Novel Oscillometric-Based Algorithm for Determination of the Ankle-Brachial Index

Peripheral arterial disease (PAD) is a highly prevalent medical condition. Patients with PAD are usually diagnosed on the basis of the ankle-brachial index. The ankle-brachial index is the ratio of ankle pressure to arm pressure after measurement of blood pressures in the arms and legs using a Doppler device. The need for dedicated equipment and trained personnel, along with the time required to perform the test, have been identified as barriers to widespread implementation of ankle-brachial index screening. The use of automated oscillometric devices for blood pressure measurement has been applied to leg pressure measurement and determination of the ankle-brachial index with variable success. It will be beneficial to investigate a reliable oscillometric-based procedure that can accurately measure leg pressures for the ankle-brachial index across the entire spectrum of PAD severity.

In a previous pilot study completed in 2009 (IRB 08-823), the investigators gathered data from N=60 subjects which allowed for mathematical analysis of oscillometric waveforms derived from the lower extremities as compared to Doppler-based measurements of blood pressure. We used signal processing analysis and regression techniques to develop a two-step algorithm which will allow for accurate interpretation of oscillometric waveforms in normal/mild vs. moderate/severely diseased limb and accurate calculation of ankle pressure across the spectrum of peripheral artery disease severity.

This proposed project will validate this novel oscillometric ABI algorithm in a population of patients who have been identified as at risk for PAD and for whom screening ABI has been recommended by multiple professional organizations (AHA/ACC and American Diabetes Association). Arm, ankle, and toe pressure measurements will be made in the supine position using Doppler, oscillometric methods, and a photoplethysmographic sensor. The ankle-brachial index and toe-brachial index will be calculated.