njit-etd2003-081 - New Jersey Institute of Technology

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HRV more information about HRV activities in both time and frequency domains can
now be revealed and be waiting for researcher's new and appropriate interpretations.
Figure 5.8 HR IIBI and power spectrum plots of a normal subject at 3 min rest paced
breathing at 8 bpm.
Figure 5.8 illustrates the case of a file from a normal subject paced breathing at 8
bpm during a 3 minutes rest period. The HRV analysis was performed using the four
different distributions with the same specifications (length of analysis window equal to
256, the length of the FFT analysis is 1024 and time resolution of 0.195 seconds). Even
though this was a poor choice of resolution, other resolutions showed even worse results.
It is evident from looking at the results in the figures that all the distributions show the
effect of respiration on HRV at about the respiration frequency of 0.133 Hz (due to
paced-breathing at 8 breaths per minute). Figures 5.9 (a) — (d) all show a band at 0.133
Hz and they all smear to other frequencies in various amounts. The 0.133 Hz bands of
the SPWV and CW distributions in figures 5.9 (b) and (c) show less smearing than the
STFT or the BJC distribution. When comparing the contour plots of the SPWV and CW
distributions, it is clear that CW shows the 0.133 Hz band with more intensity and much
sharper than the SPWV distribution. From these observations, the CW is the best
distribution of the four time-frequency distributions.