Using multifractal detrended fluctuation analysis to assess sacral skin blood flow oscillations in people with spinal cord injury.

The purpose of this study was to investigate whether the multifractal detrended fluctuation analysis (MDFA) of skin blood flow oscillations (BFO) differed between nondisabled controls and people with spinal cord injury (SCI). The study of skin BFO has shown promise for assessing blood flow control mechanisms and risk for pressure ulcers. We recruited 23 subjects, including 11 people with SCI and 12 nondisabled controls. Thermally induced maximal sacral skin BFO were measured by laser Doppler flowmetry. MDFA was used to characterize nonlinear complexity of metabolic (0.0095 to 0.02 Hz), neurogenic (0.02 to 0.05 Hz), and myogenic (0.05 to 0.15 Hz) BFO. We found that maximal vasodilation was significantly smaller in people with SCI than in nondisabled controls (p < 0.05). MDFA showed that metabolic BFO exhibited less complexity in people with SCI (p < 0.05), neurogenic BFO exhibited less complexity in people with complete SCI (p < 0.05), and myogenic BFO did not show significant differences between people with SCI and nondisabled controls. This study demonstrated the feasibility of using the MDFA to characterize nonlinear complexity of BFO, which is related to vasodilatory functions in people with SCI.