njit-etd2003-081 - New Jersey Institute of Technology

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eXogenous input (ARX) was used to estimate the impulse responses (IR) and transfer
function (TF) of the two couplings in the model. A number of indexes derived from the
IR's (peak magnitude, time of peak, delays) and TF's (gains and phases in the frequency
bands of interest) were used for subsequence statistical analysis and the assessment of
autonomic function.
The two-compartment model of RSA in the Figure is described as an ARX
representation by the equation. The coefficient of each polynomials (Bo A) were
estimated from the data by least square minimization of the prediction error W The
orders and the delays of the model were chosen by finding the model that minimized the
cross-correlation of each input and the prediction error, as well as the Minimum
Description Length (MDL)
3.13.2.2 Feedback Closed -loop ARX Model. In this section a more realistic
physiological model involving baroreflex and feedback loop. The depolarization, and
therefore contraction, of the ventricles is associated with the ejection of blood into the
aorta during systole. If one made the assumption that the volume of ejected blood is
roughly the same for each contraction, then the arterial pressure will only be a function
of the timing of the contractions. If several contractions occur close together, arterial
pressure builds, causing simultaneous stimulation and inhibition of the parasympathetic
and sympathetic branches of the ANS, respectively, resulting in a decrease in the rate of
depolarization of the SA nodal tissue. A cascade of contractions that occur further apart