njit-etd2003-081 - New Jersey Institute of Technology

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The purpose of this is to show that, although the output for different wavelets
varies, the fundamental characteristics of the wavelet transform are the same. Figure 5.29
— 5.33 show the results of these transforms. A band of cones of influence corresponding
to each minima and maxima on the BP IIBI signal at the frequency of respiration (16
bpm, 0.266667 Hz) appears in each wavelet transform representation. In addition, the
power intensity of the band is as high as the similar band shown in the normal subject
case investigated in section 5.2.2. Another band of cones of influence in the very low
frequency range (0.01 — 0.15 Hz) also exists with high energy and in longer time (from 10
seconds to 120 seconds, to 180 seconds, to 250 seconds). This matches the trend of the
blood pressure IIBI signal that can be seen in figure 5.28 (top panel, signal in green).
Among the wavelets, the Morlet wavelet again provides the best representation in terms
of time, frequency resolution and meaningful details. The band of the cones of influence
at 0.266667 Hz modulated slightly indicating that the BPV is also dominated by the
respiration signal and is also not a stationary signal.
There are also many interesting observations unveiled from the data and the
experimental setup of the normal and COPD subjects. The first was the interplay of the
two opposing physiological factors that were simultaneously revealed in the timefrequency
analysis of the heart rate variability signal during stressful exercise conditions
for normal subjects and during rest for COPD patients. Another was the compensation of
the HR in COPD by having a cyclic modulation at about 4 to 5 minutes while normal
subjects took longer to have these HR modulations and in a more random nature.