Integrative analysis of intracranial pressure and R-R interval signals: a study of ICP B-wave using causal coherence.

Causal coherence analysis was applied to beat-to-beat mean intracranial pressure (ICP) and RR interval signals that were recorded from twelve normal pressure hydrocephalus patients. Data were organized into two groups including an ICP B-Wave group and a control baseline group. Maximal classic coherence between ICP and RR interval within [0.04-0.15] Hz was found to be significantly greater than zero for both B-wave and control groups. Causal coherence analysis further revealed that feedforward coherence due to RR interval's effect on ICP always exists for both B-wave and baseline ICP state while feedback coherence from ICP to RR interval was enhanced during the occurrence of B-wave.