Transient interactions between blood pressure,respiration and heart rate in man

Auto regressive spectral estimation techniques have been used to follow transient interactions between mean blood pressure, respiration and heart rate. This demonstrates that these inter-relationships are variable. It is concluded that while central modulation of heart rate is the major factor in the interactions, when the heart rate is fixed, peripheral modulation of the blood pressure by respiration is clearly demonstrated.     

The variability characteristics of the arterial pressure in man and animals

The development of computer monitoring methods over haemodynamic parameters has made possible on objective quantitative estimation of blood pressure (BP) variability in humans and animals which can have both periodic and aperiodic feachers. The spectral analysis of spontaneous BP fluctuations reveals presence of several power peaks main of which, as well as in heart rate variability, reflect sympathetic and parasympathetic activity. Both in hypertensive patients and animal models of arterial hyper tension BP variability is higher, but its relationship with BP level is not realized in a simple causal scheme. Observations in prehypertensive period demonstrate an opportunity of dissociation between rates of BP level and variability increase. The pharmacological analysis permisses to suggest the sympathetic activation as the main cause of BP destabilization. Despite a leading role of baroreceptor reflex (BR) in damping of evoked BP fluctuations, its role in regulation of spontaneous variability seems to be ambiguous. The studies excluding episodes of locomotor and other activities from the curve analysis do not confirm a correlation between BP variability and BR gain. The spectral analysis of BP lability in animals with denervated mechanoreceptor zones has revealed BR effective control only of a low and superlow frequency areas (less than 0.07 Hz). The study of the regional blood flows in sinoartic denervated rats has concluded that the increase of their autonomy is the main reason of BP lability. The offset of BR efferent limb by ganglionic blocking agents or desympathization leads to analogical BP lability. Thus, BP variability seems to be a reflection of functional efficiency of BP stabilization mechanisms. Considering that on its origin, connections with other haemodynamic parameters, amplitude and frequency characteristics is a complex phenomenon, no one of mechanisms is an universal instrument of its regulation.