Vascular Assessment in Patients With a Lower Limb Wound: A Correlational Study of Photoplethysmography and Laser Doppler Flowmetry Toe Pressure Techniques

Abstract

Background: Vascular assessment of the lower limbs is essential in patients with diabetes. In the presence of noncompressible arteries, the ankle brachial index (ABI) can either be inconclusive or provide false-positive results. Toe pressure measurement has been suggested as an alternative as a noninvasive method for detecting peripheral arterial disease (PAD). Toe pressure measurement can be performed either by photoplethysmography (PPG) or by Laser Doppler flowmetry (LDF). The aim of this study was to determine correlations between the two techniques in order to promote the use of PPG in clinical practice. Methods: This was a prospective correlational study of 108 consecutive recruited adult patients, with and without diabetes, with at least one lower limb wound from a University-affiliated hospital wound care clinic. Toe pressure measurements were both performed with PPG and LDF devices. Results: Mean toe pressure values for PPG and LDF were, respectively, 83.7 (SD 35.4) and 79.5 (SD 32.0) mmHg (with a paired t-test 3.969, P < 0.01). In patients with at least one lower limb wound, a strong linear relation was found between PPG and LDF toe pressure techniques with a Pearson’s r correlation coefficient of 0.920 (P < 0.001). Conclusions: PPG and LDF toe pressure techniques are equivalent in patients with at least one lower limb wound, irrespective of the presence of diabetes. Therefore, in the presence of an ABI with inconclusive results, such as in a patient with noncompressible vessels, both toe pressure techniques can be used for assessing the vascular supply of the lower limb with a wound.