njit-etd2003-081 - New Jersey Institute of Technology

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2. Interpretation of the transfer relations has been limited by insufficient
characterization of the central and peripheral mechanisms, which mediate these
relations (e.g. — the sino-atrial (SA) nodal responses, the mechanical coupling
relations, and the baroreceptors).
In this research the author uses the same model of the cardiovascular system for
normal subjects using the experimental data taken from ten normal healthy subjects. In
the HRV modeling task, the transfer functions of the HRV model is estimated from a
black box model using the actual respiration (rsp) data as input and
1) The iibi signal derived from the actual ECG as output, and/or
2) The actual blood pressure data as output.
In previous studies the transfer or frequency response functions were all
calculated using the cross spectral method. The autospectra of the input signal (e.g.
respiration), S1 (f) and of the output signal (e.g. — HR), Soo (f) were estimated. The
cross-spectra, St, (f ), between the input and output signals were also computed. Then,
the complex transfer function, H(f), and its magnitude and phase, |H(f)| and 0(f)
where R and I are the real and imaginary components of the complex transfer function.