Technique for the quantification of transient quadratic phase couplings between heart rate components

A technique for the time-variant analysis of quadratic phase coupling (QPC) in heart rate data is introduced and tested in 6 human neonates during qui et sleep. The set up of the approach is based up on the assumption that QPC s in the heart rate variability (HRV) are related to amplitude modulation e ffects. The application of the biamplitude deals with the detection of the coupling pattern and the bicoherence is used for the statistical quantifica tion of coupling. By means of the results of bispectral analysis the time-v ariant processing has been adapted. The frequency-selective complex demodul ation of the HRV leads to the envelope of the respiratory sinus arrhythmia (RSA), this has been used as one input for a time-variant coherence analysi s. The other input is the low-pass filtered 10-second-rhythm of the HRV. A time-continuous quantification of the QPC, caused by amplitude modulation ( 10-second-rhythm modulates the RSA), is possible using this approach. Accor ding to our observed results in neonatal HRV both a phase co-ordination bet ween the 10-second-rhythm and RSA as well as a non-linear coupling (amplitu de modulation) between these HRV components can be seen.