Relationship between Sacral Skin Blood Flow Oscillations and Vasodilatory Functions in People at Risk for Pressure Ulcers

The role of microvascular function in the risk for pressure ulcers can be assessed by studying the changes of skin blood flow oscillations (BFO) in response to causative factors of pressure ulcers such as local heating [1]. Previous studies, using either Fourieror wavelet-based spectral analysis, provide essential contributions to the understanding of the control mechanisms of BFO [2]. Wavelet analysis of skin BFO reveals five characteristic frequencies, associated with endothelial metabolic activities, sympathovagal neurogenic activities, vascular myogenic activities, breathing movements, and heart beats. This method allows clinicians and researchers to non-invasively assess microvascular dysfunction in various pathological populations. However, wavelet analysis is a linear method and cannot characterize the nonlinear properties embedded in BFO of the cardiovascular system. The cardiovascular system is a complex, nonlinear dynamical system, and skin blood flow regulation is therefore a nonlinear process [3].