njit-etd2003-081 - New Jersey Institute of Technology

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This section looks at some applications of the wavelet time frequency distribution
techniques. At the same time, comparisons of different wavelets are done to find the best
wavelet for the sympathovagal case.
The wavelet distributions were calculated using our wavelet time frequency
distribution software. The program then analyzed the representative heart rate and blood
pressure RBI signals of a COPD subject. The 3D, contour plots and the activity plots
were obtained for the entire file by calculating the areas under the LF, HF ranges for each
instant of time. The sympathovagal balance (the ratio of the LF to the HF range, LF:HF)
was also obtained. As mentioned earlier drug studies indicate that the LF range is a
mixture of sympathetic and parasympathetic division activity. The ratio is an indication
of both reciprocity and non-reciprocity [50].
Figures 5.18 — 5.27 display the 5-minute activity plots of a COP subject at rest
breathing at 16 breaths per minute using the Morlet, Meyer, Daubechies 4, Mexican Hat
and Haar wavelet. The even figures (5.18, 5.20, 5.22, 5.24 and 5.26) present the low
frequency, the high frequency and the ratio of low frequency to high frequency as
obtained by summing the areas under the curves in the LF and HF bands at each instant of
time throughout the whole experiment period. The odd figures (5.19, 5.21, 5.23, 5.25
and 5.27) present the normalized low frequency, the normalized high frequency and the
normalized ratio of the low frequency to high frequency. The normalized LF and HF
activity plots are obtained by dividing at each instant of time the LF and HF power by the
sum of both as follows: