Development and evaluation of a cardiac coherence index for sleep analysis

Abstract

Cardiac coherence measurement is an established technology in biofeedback systems for stress release. Studies have typically been conducted with participants during ordinary waking consciousness, yet cardiac coherence during sleep may be even more important in illness prevention and health promotion. We investigated whether it was possible to develop an alternative effective technology: the Cardiac Coherence Index (CCI), for sleep analysis. The CCI is based on heart inter-beat interval spectral entropy and autonomic nervous system resonance analysis. We tested the hypothesis that the CCI could be a way to assess sleep quality and eventually as a tool to assess consciousness states during sleep. Our analysis suggests that high CCI corresponds to deep sleep stage, low CCI to awake state, and medium CCI to dream state. These findings further suggest that the CCI method is potentially a useful tool for the study of consciousness and as a home-based system for sleep management.

Keywords:

• cardiac coherence
• consciousness
• quality of life
• sleep continuity
• sleep stages
• stress

Acknowledgements

This work is based on research supported by the University of Zululand and the South African National Research Foundation (NRF). Any opinion, finding, conclusion, or recommendation expressed in this material is that of the author(s) and the NRF does not accept any liability in regard thereto.

Notes

1 The reason for choosing this duration of segment is that it coincides with gold standard polysomnography analysis.

2 The ANS resonant frequency is different in every person but always close to 0.1Hz. Ideally, we should measure for the individual resonant frequency of each person.