Physiological regularity of cardiovascular and spontaneous respiration series in healthy humans

All cardiovascular and respiratory series are characterized by a variable regular dynamics in human beings, underlying the complexity of the interactions among the control system, the target organs and external/endogenous stimuli. Conditional corrected entropy (CCE) provides information about the regularity of dynamic signal variations: the technique has been applied to R-R interval, non-invasive systolic arterial pressure, diastolic arterial pressure and spontaneous respiratory signals from 15 healthy subjects monitored during quiet supine resting. As a regularity index (RI), ranging from 0 to 1, the difference between the minimum CCE and 1 has been calculated (mean value ±SD), resulting in an RI of 0.263±0.090 for respiration, 0.500±0.080 for systolic arterial pressure and 0.459±009 for diastolic arterial pressure. Heart rate and respiratory dynamics appear to be more complex than arterial pressure dynamics