There are limited non-invasive methods to assess lower extremity arterial injuries in the emergency department (ED) and pre-hospital setting. The ankle-brachial index (ABI) requires careful auscultation by Doppler, an approach made difficult in noisy environments. We sought to determine the agreement of the ABI measured using the pulse oximeter plethysmograph waveform (Pleth) with auscultation by Doppler in a controlled setting. A secondary outcome sought to examine the agreement of ABI by automated oscillometric sphygmomanometer (AOS) with Doppler.

We measured blood pressure in the right upper and lower extremities of healthy volunteers using: (1) Doppler and manual sphygmomanometer; (2) Pleth and manual sphygmomanometer; and (3) AOS. The Bland-Altman approach to assessing agreement between methods was used comparing mean differences between ABI pairs to their means for Doppler versus Pleth and Doppler versus AOS. The intraclass correlation coefficient (ICC) from mixed effects models examined intra- and inter-rater reliability.

Among 100 participants with normal ABI the mean ABI (95%CI) were Doppler 1.11 (0.90–1.33), Pleth 1.10 (0.91–1.30), and AOS 1.10 (0.90–1.30). The ABI difference (95% CI for limits of agreement) were 0.01 (−0.20,0.18) for Doppler-Pleth and 0.02 (−0.26, 0.22) for Doppler-AOS. The ICC for the Doppler-Pleth comparison (ICC = 0.56, 95% CI 0.47–0.63) was greater than for the Doppler-AOS (ICC = 0.32, 95% CI 0.19–0.43).

The ABI measured using the Pleth has a high level of agreement with measurement by Doppler. The AOS and Doppler have good agreement with greater measurement variability. Pleth and AOS may be reasonable alternatives to Doppler for ABI.