A device for noninvasive assessment of vascular impairment risk in the lower extremity

The repeatability and resolution of the clinical gold standard of vascular assessment, the ankle-brachial index (ABI), was compared to that of a new device that dynamically assesses tissue perfusion during external loading utilizing laser Doppler flowmetry. Eight subjects of varying levels of vascular impairment were tested in successive weeks using two different sites on the subject's posterior calf. These new measures included the perfusion decrease as well as the unloading delay during cyclic loading. Some new dynamic tissue perfusion measures demonstrated comparable levels of reproducibility with the ABI (e.g., 10%-20%). Only the unloading delay showed potentially enhanced resolution over ABI measures. The perfusion decrease showed little resolution, and the remaining parameters exhibited too great variability (25%-90%). The unloading delay associated with the reperfusion response during cyclic loading displayed the greatest combination of reproducibility and differentiation between subject groups of varying levels of vascular impairment. The preliminary results of this pilot study were also used to estimate sample sizes necessary to detect possible significant (P<0.05) differences between subject groups for all measured perfusion parameters. From these calculations, at least 30 subjects are needed for future study in each of the five subject groups.