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Multiscale entropy of laser Doppler flowmetry signals in healthy human subjects
Anne Humeau1, Benjamin Buard, Guillaume Mahé
1Laboratoire d'Ingénierie des Systèmes Automatisés (LISA), Université d'Angers, 62 Avenue Notre Dame du Lac, 49000 Angers, France. anne.humeau@univ-angers.fr
Insights
This study introduces multiscale entropy analysis for laser Doppler flowmetry (LDF) signals, revealing distinct complexity changes at specific scales in healthy subjects. This method offers a potential stationary signature for peripheral cardiovascular regulation.
Area of Science:
- Cardiovascular Physiology
- Biomedical Signal Processing
- Complexity Science
Background:
- Cardiovascular system (CVS) regulation is studied centrally via heart rate variability (HRV) and peripherally via laser Doppler flowmetry (LDF).
- Multiscale entropy (MSE) analysis has provided physiological insights into central CVS regulation but remains unexplored for peripheral LDF signals.
- Peripheral CVS studies using multiscale approaches are a recent development.
Purpose of the Study:
- To perform the first multiscale entropy analysis on laser Doppler flowmetry (LDF) signals recorded from healthy subjects.
- To investigate the scale-dependent complexity of peripheral cardiovascular regulation using LDF data.
Main Methods:
- Processed LDF signals from seven healthy subjects with a sampling period of T=50 ms.
- Analyzed coarse-graining scales ranging from T to 23T.
- Validated the multiscale entropy algorithm using synthetic signals with known theoretical entropy values.
Main Results:
- Observed a non-monotonic evolution of LDF signal multiscale entropy, peaking around 7T and minimizing around 18T.
- Identified two distinct scales where LDF signal complexity significantly changes.
- Contrasted these findings with HRV signals, which typically show monotonic increases in multiscale entropy.
Conclusions:
- Multiscale entropy analysis of LDF signals in healthy individuals demonstrates scale-dependent variations.
- The consistent variation pattern suggests MSE could serve as a stationary signature for LDF signals, overcoming probe-position and subject dependency.
- Further research is warranted to explore the diagnostic potential of LDF multiscale entropy in cardiovascular assessment.
Purpose:
The cardiovascular system (CVS) regulation can be studied from a central viewpoint, through heart rate variability (HRV) data, and from a peripheral viewpoint, through laser Doppler flowmetry (LDF) signals. Both the central and peripheral CVSs are regulated by several interacting mechanisms, each having its own temporal scale. The central CVS has been the subject of many multiscale studies. By contrast, these studies at the level of the peripheral CVS are very recent. Among the multiscale studies performed on the central CVS data, multiscale entropy has been proven to give interesting physiological information for diagnostic purposes. However, no multiscale entropy analysis has been performed on LDF signals. The authors' goal is therefore to propose a first multiscale entropy study of LDF data recorded in healthy subjects.
Methods:
The LDF signals recorded in the forearm of seven healthy subjects are processed. Their period sampling is T=50 ms, and coarse-graining scales from T to 23T are studied. Also, for validation, the algorithm is first tested on synthetic signals of known theoretical multiscale entropy.
Results:
The results reveal nonmonotonic evolution of the multiscale entropy of LDF signals, with a maximum at small scales around 7T and a minimum at longer scales around 18T, singling out in this way two distinctive scales where the LDF signals undergo specific changes from high to low complexity. This also marks a strong contrast with the HRV signals that usually display a monotonic increase in the evolution of the multiscale entropy.
Conclusions:
Multiscale entropy of LDF signals in healthy subjects shows variation with scales. Moreover, as the variation pattern observed appears similar for all the tested signals, multiscale entropy could potentially be a useful stationary signature for LDF signals, which otherwise are probe-position and subject dependent. Further work could now be conducted to evaluate possible diagnostic purposes of the multiscale entropy of LDF signals.
