Complexity of heart rate, blood pressure and respiration disclosed by pattern fractal analysis

The complex nature of physiological signals, such as heart rate, arterial pressure and respiration is an inherent property of the homeostasis of the cardiovascular and the respiratory system: this complexity should be well represented by fractal analysis. To test this hypothesis, cardiovascular and respiratory signals have been evaluated by a modified algorithm, Pattern Fractal Analysis, which has been applied to multiparametric recordings in healthy subjects during quiet supine resting. Signals have been analysed over consecutive 256-beat long windows; in all subjects, the Pattern Fractal Dimension has been extracted for each signal. Both the Fractal Dimension time course during the recording session and the overall average individual and population values have been considered. Pattern Fractal Analysis seems able to detect and quantify the complexity of biological signals; the roughness of respiratory and RR intervals resulting is more evident than for blood pressure signals.