ABSTRACT
The concept of sympathetic or vagal tone has been often alluded to by physiologists and clinicians, as described by W. B. Cannon; the main obstacle for making use of this concept has been related to the difficulty of its assessment. Reflex bradycardia accompanying rises in arterial pressure has traditionally been considered the result of the stimulation of a restricted reflexogenic area. Circulation and respiration, which are strictly related transport functions, are both based on discontinuous events and oscillations of various orders characterize variables such as arterial pressure and heart period. The push-pull of sympatho-vagal interaction is of paramount importance not only for physiological life, but for disturbances of regulation such as arterial hypertension. To explore this interaction, in steady-state conditions throughout the frequency domain, seems to open new perspectives. The computer program automatically calculates the model, i.e., the autoregressive coefficients, that provides best statistical estimate of the spectral distribution and prints out the power and frequency of every spectral component.
