Trajectory analyses of time-varying multivariate cardiovascular dynamics based on a distance measure

The authors have investigated the cardiovascular dynamics during physiological states such as sleep and wakefulness. Its time-dependent properties during transient states are modeled as time-varying multivariate autoregressive processes. The trajectory of multivariate dynamics are described in terms of Kullback-Leibler Divergence. The cardiovascular dynamics during the state transition from wakefulness to slow wave sleep (SWS) and from rapid eye movement sleep to SWS are tracked as their trajectories in the metric system space, which show the geometrical structure peculiar to the respective state transition