Automatic ankle pressure measurements using PPG in ankle-brachial pressure index determination

Abstract

Objective: To evaluate a new technique using a photoplethysmographic (PPG) probe for automatic ankle pressure measurements. Design: Comparative study on two techniques for ankle pressure measurement. Setting University hospital. Material: Thirty-five patients with leg arterial disease and eight healthy volunteers. Ankle-brachial indices (ABPI) were measured using conventional CW Doppler technique and PPG-based prototype equipment for the ankle pressure recordings. Chief outcome measures: ABPIs calculated from CW Doppler and PPG ankle pressure measurements. The PPG signals were analysed both by visual judgement and by a software based, automatic algorithm. Main results: The mean difference between ABPIs calculated from CW Doppler recordings and PPG (visual analysis) was -0.01 (limits of agreement (±two standard deviations) +0.16 to -0.19). The correlation coefficient was 0.93. When the algorithm was used, the mean difference (CW Doppler-PPG) was 0.05 (limits of agreement 0.28 to -0.18, r=0.89). Conclusions: The PPG method is a promising technique with an inherent potential for automatisation of the ankle pressure measurements, thereby reducing the observer-dependency in ABPI recordings. © 2005 Elsevier Ltd. All rights reserved.