D. Hoyer et al., ESTIMATION OF NONLINEAR COUPLINGS ON THE BASIS OF COMPLEXITY AND PREDICTABILITY - A NEW METHOD APPLIED TO CARDIORESPIRATORY COORDINATION, IEEE transactions on biomedical engineering, 45(5), 1998, pp. 545-552
Nonlinear coordination is an essential property of the complex functio
ning of the autonomic nervous system. Therefore, the coupled behavior
of heart rate fluctuations (HRF) and respiratory movements (RM) was an
alyzed on the basis of their joint reconstruction in the phase space.
Independence measures of complexity and predictability were approximat
ed from the correlation integrals which enabled the strength of cardio
respiratory couplings to be quantified. These measures were validated
in a simulation study of two coupled nonlinear oscillators in dependen
ce on their coupling strength and respective synchronization effects.
The cardiorespiratory coordination during quiet sleep and active sleep
of newborn piglets was quantified by means of the proposed independen
ce measures of complexity and predictability. The difference of those
measures between the sleep states investigated was more significant th
an the difference of the respective linear coherence peaks.