Steady-state time series and code

Pressure-flow travelling waves are a key topic for understanding arterial
haemodynamics. However, wave trasmission and reflection processes induced
by body posture changes have not been thoroughly explored yet. Current
in-vivo research has shown that the amount of wave reflection detected at
the central level (ascending aorta, aortic arch) decreases during tilting
to the upright position, despite the widely-proved stiffening of the
cardiovascular system (CVS). Moreover, it is not known whether the
optimized configuration of the arterial system typical of the supine
condition - i.e., enabled propagation of direct waves vs. trapping of
reflected waves, protecting the heart - is preserved or not after posture
changes.  To shed light on these aspects, we propose a multiscale
modelling approach to inquire into posture-induced arterial wave dynamics
elicited by simulated head-up tilting. In spite of remarkable remodelling
of the human vasculature following posture changes, our analysis shows
that: (i) vessels lumens at arterial bifurcations remain well matched in
the forward direction; (ii) the reduced wave reflection observed at the
central level seems to be caused by backward propagation of weakened
pressure waves produced by cerebral autoregulation; and (iii) backward
wave trapping is preserved upon orthostatic stress.