Nonlinear chaotic dynamics of mean arterial pressure after carotid baroreceptor isolation

The relationships between the carotid baroreflex and the nonlinear chaotic dynamics of short-term arterial blood pressure control was investigated. Studies in conscious dogs with their baroreceptors either intact (control group: n=7) or surgically isolated (intervention group: n=7), demonstrated deterministic chaotic behavior in mean arterial blood pressure. To assess nonlinear dynamical behavior, we constructed phase-space trajectories from the time series data. The correlation dimension of the reconstructed trajectories was measured using the Grassberger-Procaccia algorithm. A significant increase (P<0.01) in the correlation dimension was measurable between the control (3.46±0.38) and intervention groups (4.59±0.23). Sensitive dependence on initial conditions as determined by the largest Lyapunov exponents, revealed a significant (P<0.01) decrease in the intervention group (0.261±0.03) when compared with the control group (0.40±0.04). Surrogate data analysis involving the removal of essential nonlinear characteristics from the original data using phase randomisation, revealed that the correlation dimension did not converge over the range of embedding dimensions possible, and that the nonlinear forecasting ability decreased