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

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 anti PPG ankle pressure measurements. The PPG signals were analysed both by visual judgement anti 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 algorithin 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.