Ventilation related heart rate oscillations – respiratory sinus
arrhythmia (RSA) – originate in human from several mechanisms.
Two most important of them – the central mechanism (direct
communication between respiratory and cardiomotor centers),
and the peripheral mechanism (ventilation-associated blood
pressure changes transferred to heart rate via baroreflex) have
been described in previous studies. The major aim of this study
was to compare the importance of these mechanisms in the
generation of RSA non-invasively during various states by
quantifying the strength of the directed interactions between
heart rate, systolic blood pressure and respiratory volume
signals. Seventy-eight healthy volunteers (32 male, age range:
16.02-25.77 years, median age: 18.57 years) participated in this
study. The strength of mutual interconnections among the
spontaneous beat-to-beat oscillations of systolic blood pressure
(SBP), R-R interval (RR signal) and respiration (volume changes –
RESP signal) was quantified during supine rest, orthostatic
challenge (head-up tilt, HUT) and cognitive load (mental
arithmetics, MA) using bivariate and trivariate measures of
cardio-respiratory information transfer to separate baroreflex and
nonbaroreflex (central) mechanisms. Our results indicate that
both basic mechanisms take part in RSA generation in the intact
cardiorespiratory control of human subjects. During orthostatic
and mental challenges baroreflex based peripheral mechanism
becomes more important