title: Transitions in skin blood flow fractal scaling: the importance of fluctuation amplitude in microcirculation.
abstract: Detrended fluctuation analysis (DFA) of laser Doppler flowmetry (LDF) time series from volar skin reveals three scaling regions: cardiac, cardio-respiratory and local. Scaling exponents, slopes (αC, αCR and αL) of the straight lines, in these regions indicate correlation properties of LDF signal. Transitions from uncorrelated to positive in cardiac (αC) and positive to negative correlations in the cardio-respiratory (αCR) exponent have been observed for vasodilatation signals in response to local heating. However, positive correlation in local region (αL) did not change with vasodilatation. We studied whether the transitions in scaling exponents are correlated with the increase in peak to peak fluctuation amplitude (AF) of LDF signal. LDF signals were normalized to unity using average values of their pulsatile parts: baseline and saturation signals. If AF of normalized LDF signal is ≥0.5, we observed transitions in αC and in αCR but not in αL, in healthy subjects. It is suggested that the transition from positive to negative correlation in αCR with increasing amplitude may be explained by intact arteriolar myogenic activity in healthy young (Y) and middle aged (MA) subjects. In contrast, we did not observe transition in αCR suggesting impaired myogenic activity in patients with essential hypertension (EHT).
authors.affiliation: Department of Biophysics, Faculty of Medicine, Eskişehir Osmangazi University, 26480 Eskişehir, Turkey. Electronic address: hesen@ogu.edu.tr.
authors.forename: Hamza
authors.initials: H
authors.lastname: Esen
authors.affiliation: Department of Biophysics, Faculty of Medicine, Eskişehir Osmangazi University, 26480 Eskişehir, Turkey.
authors.forename: Necmi
authors.initials: N
authors.lastname: Ata
authors.affiliation: Department of Biophysics, Faculty of Medicine, Eskişehir Osmangazi University, 26480 Eskişehir, Turkey.
authors.forename: Ferhan
authors.initials: F
authors.lastname: Esen
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity; D016022:Case-Control Studies; D005260:Female; D017709:Fractals; D006801:Humans; D006973:Hypertension / Q000175:diagnosis / Q000503:physiopathology*; D017078:Laser-Doppler Flowmetry / Q000379:methods*; D008297:Male; D008833:Microcirculation; D008875:Middle Aged; D008955:Models, Cardiovascular; D010363:Pattern Recognition, Automated; D011673:Pulsatile Flow; D012039:Regional Blood Flow; D012815:Signal Processing, Computer-Assisted; D012867:Skin / Q000098:blood supply*; D012881:Skin Temperature; D013997:Time Factors; D014664:Vasodilation
keywords: Blood flow; Essential hypertension; Fluctuation amplitude; Forearm skin; Transition in fractal scaling