a la physique de l'information - Lisa - Université d'Angers

622 A Humeau et al
(a) (b)
(c)
Figure 3. (a) HRV signal from a healthy subject at rest, in the supine position. (b) Skin LDF signal
recorded in a healthy subject at rest in the supine position. The LDF probe is positioned on the
ventral face of the forearm. (c) Skin LDF signal recorded in a healthy subject at rest in the supine
position. The LDF probe is positioned on the distal phalanx of the second finger (palmar side of
the index).
who had two LDF probes, the recordings made in the supine position were preceded by 8 min
of recordings (ECG + two LDF signals) in the upright position.
After acquisition, ECG signals were processed to obtain the HRV data: a computer
program was developed by our group (written in Matlab, The MathWorks, Inc.) to
automatically detect the R peaks of the ECG time series; the results given by the automatic
detection were then visually checked and corrected if needed, and the R–R intervals were
computed. HRV and LDF data are shown in figure 3. In what follows, the previously described
methodology estimating the multifractal spectra is applied on LDF and HRV signals.
3.2. Multifractal spectra obtained in the supine position
For the supine position, 16 384 samples of LDF signals (∼11 min of data) and 1024 samples
of HRV data (this corresponds to a mean of 14.19 min of ECG signals for the 14 subjects
studied in this position) were processed. Partition functions of LDF and HRV data for one
subject are shown in figures 4(a) and (b), respectively. The average multifractal spectra of
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