Autonomic Stress in Plateau Waves of Intracranial Pressure: Spectral Mutual Information Rate Analysis

Plateau waves (PW) in intracranial pressure (ICP) often manifest in traumatic brain injury (TBI), presenting as abrupt increases in ICP exceeding 40 mmHg, accompanied by a decrease in cerebral perfusion pressure (CPP). The occurrence of PWs is a significant cerebrovascular phenomenon with potentially devastating effects for the patient, which is reflected in heart rate variability (HRV), typically assessed by RR intervals in electrocardiographic recordings. This study employs the spectral formulation of mutual information rate (MIR) to dynamically quantify the coupling between RR intervals and ICP across 27 episodes of PWs from 7 patients with TBI. Furthermore, this measure of information theory can be decomposed into entropy rate components related to complexity, each of which can be integrated into frequency bands with physiological significance. Our findings demonstrate the feasibility of using non-parametric spectral measures to analyze cardio-cerebral interactions. Specifically, during PW events, complexity decreases across all frequency bands examined, indicating increased regularity in RR intervals. Changes in dynamic coupling during PW may be linked to autonomic nervous system dysfunction, potentially stemming from the interaction between the parasympathetic system and ICP. These results suggest the potential inclusion of information-theoretic measures into intensive care units (ICU) monitors to improve the prediction and management of these stress episodes.