(CR-058) The Plantar-palmar Index with near Infrared Spectroscopy Replaces the Ankle-brachial Index for Noninvasive Evaluation of Vascular Perfusion and Peripheral Arterial Disease
Introduction: The Ankle Brachial Index is a widely used diagnostic technique for peripheral artery disease. The ABI procedure can be time-consuming, labor intensive, and uncomfortable for patients.As a screening technique the ABI has poor sensitivity and can be unreliable in diabetic patients1,2.
Methods: Study subjects included normal-healthy, patients with DFU, patients with known PAD and complications of PAD.The ABIs and pulse volume recordings were accomplished and recorded in all subjects (MESI mTABLET).Near infrared spectroscopy (NIRS) (SnapshotNIR) is an imaging device that measures oxygenated and de-oxygenated hemoglobin in tissues to create an image of tissue oxygen saturation3. NIRS is non-invasive and has demonstrated efficacy assessing tissue perfusion in patients with PAD4.NIRS images were obtained of the palm-hand and the plantar-foot with all subjects lying in the supine position and an average STO2 was obtained. The Plantar-Palmar Index is similar to the ABI ratio (Plantar STO2 / Palmar STO2).
Results: A series of 90 limbs were studied. The cohort included healthy subjects and those with various degrees of PAD. ABIs and PVRs were obtained, and NIRS imaging PPI ratios were calculated for all limbs.PVRs were interpreted and classified as Normal (n=48), Mild (n=32), Moderate (n=7) and Severe (n=3).The Estimated Margin Means of the PPI in reference to the PVR were calculated; Normal 1.041, Mild 1.148, Moderate 1.457, Severe 1.570 with 95% CI’s Normal (0.998, 1.084), Mild (1.095, 1.201), Moderate (1.345, 1.589) and Severe (1.399, 1.741).ANOVA results across all 4 groups yielded p< 0.001. Pairwise comparison showed significance of Normal-Mild p< 0.005, Normal-Moderate p< 0.001 and Normal-Severe p< 0.001.
Discussion: While the ABI remains deeply entrenched in clinical assessment of PAD, the challenges and limitations associated with this test have been well recognized.As evidence, a recent proposed LCD (L35041) originally stated “An ankle-brachial index (ABI) should be taken for patients with a questionable pulse deficit…”Based on clinician input his language was modified to read “An objective, non-invasive measure of perfusion/oxygenation to determine if there is adequate flow for wound healing is helpful.”5 The positive correlation of NIRS PPI with ABI has been previously reported.6 This study suggests that NIRS-PPI also correlates well with PVR evaluations and could replace the ABI/PVR as the method for assessing both the presence and severity of PAD. Further research and clinical trials are essential to validate these results and establish standardized clinical protocols for implementation.
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