MONOFRACTALITY IN RR HEART RATE BY MULTIFRACTAL TOOLS

Multifractal formalism is tested if it can work as a robust estimatorof monofractals when scaling intervals are fixed. Intervals for scaling areselected to be consistent with known frequency bands of power spectralanalysis used in estimates of heart rate variability: low frequency (LF),very low frequency (VLF), and ultra low frequency (ULF). Tests on frac-tional Brownian motions and a binomial cascade are performed to vali-date popular multifractal methods: Wavelet Transform Modulus Maximaand Multifractal Detrended Fluctuation Analysis. Then the methods areapplied to identify monofractal elements of control processes driving theheart rate. A transition is found in the dynamic organization of autonomicnervous system control of the heart rate related to the change in scalingintervals. The control over the diurnal heart rate is of a multifractal typewhen considered in LF and of a monofractal type when observed in ULF.Additionally, this transition affects on a switch in a relation between widthsof diurnal and nocturnal multifractal spectra.PACS numbers: 95.75.Wx, 87.90.+y, 89.75.Da, 05.65.+b